Author: bstansberry(a)jboss.com Date: 2008-02-22 18:24:53 -0500 (Fri, 22 Feb 2008) New Revision: 14347 Added: core/trunk/documentation/jbosscache2/ core/trunk/documentation/jbosscache2/README core/trunk/documentation/jbosscache2/pom.xml core/trunk/documentation/jbosscache2/src/ core/trunk/documentation/jbosscache2/src/main/ core/trunk/documentation/jbosscache2/src/main/docbook/ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/Hibernate_JBC2_Reference.xml core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/architecture.xml core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/concepts.xml core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/configuration.xml core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/eviction.xml core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/introduction.xml core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/preface.xml core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/hibernate_logo_a.png core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/multi-cache.png core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/single-cache.png core/trunk/documentation/jbosscache2/src/main/docbook/en-US/legal_notice.xml Log: [HHH-3127] Create reference guide for the Hibernate/JBC2 integration Property changes on: core/trunk/documentation/jbosscache2 ___________________________________________________________________ Name: svn:ignore + target .project .settings Added: core/trunk/documentation/jbosscache2/README =================================================================== --- core/trunk/documentation/jbosscache2/README (rev 0) +++ core/trunk/documentation/jbosscache2/README 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,176 @@ +THE HIBERNATE DOCUMENTATION +christian(a)hibernate.org + +COPYRIGHT NOTICE: This documentation system and all its source files are +licensed under the GNU Lesser Public License (LGPL). Authors and translators +retain the copyright of their work. All font and other build files (the DocBook +system) are property of their respective copyright holders. Some of the files +(especially font files) might require a license from the respective vendor; you +are responsible to check and obtain these licenses as necessary before you use +and/or distribute these files. + + +Preface + +The Hibernate documentation is a modular documentation, it uses +various XML files (written with the DocBook DTD) and a Java-based +build process to generate HTML and PDF output. Use a simple text +editor with XML support, such as JEdit, to edit the source files. You +will need Java and Ant installed for the output generation. The toolset +is Java only and should work on any operating system. + +Note: Always use 4 spaces to indent, no tabstops (code examples will +be broken otherwise). + + +1. How to get it + +Check out a copy of Hibernate from the repository. A regular +Hibernate download will not contain the build process for the +documentation, only the PDF/HTML output, use the repository! +See http://www.hibernate.org/Download/DownloadOverview + + +2. Working on the original language + +The original and master language is English, hence the "en" subdirectory +in /doc/reference/ is authorative. We use "id" and "revision" attributes on +XML elements to track changes. Here are the rules, they are mandatory: + +2a. Changing existing content involves an update of the "revision" of the XML +element you are working on (e.g. a <sect1>, <sect2> or even a <para>). + +If a <sect1> has a revision="1", you update it to "2" after updating the +content in that section. + +You can also add a revision attribute to an element if there is none, +start with revision="1". You should not add a revision attribute to each +paragraph, try to only add/use revision attributes to sections. You can' +t add a revision attribute to elements without an "id" attribute! + +2b. Adding new content involves adding new elements (even new files), such +as <sect1>, <para> and so on. Any new element (or its new parent element) +needs an "id" attribute if the new content is to be included in the change +tracking. If you add a section, give it a unique short text +identifer, look at the parent element's identifier for the common prefix. + +2c. Deleting content involves removing old elements. Just remove them and +make sure that the parent elements revision is updated, if the removed +element did not itself have an identifer and a revision. If you remove an +element with its own identifier, everything is fine and no other changes are +necessary. + + +3. Starting a new language + +If you start a translation for a new language, you have to copy +the default language (English) and start an initial translation. + +3a. First, duplicate the default language "en" by duplicating the directory +/doc/reference/en. For example, a new German translation +will be a copy of that directory in /doc/reference/de. We use the ISO +codes to name the language subdirectories. + +3b. You also have to add your new language to the language build file, +/doc/reference/build.xml. Look for the lines that have a "TRANSLATOR" +comment and duplicate them. Change the default "en" to your language +code, every language listed here will be included in both the PDF/HTML +generation and the revision diff change tracking reports (discussed later). + + +4. The initial translation + +If you just copied the default language, start translating the DocBook +XML modules and illustrations in the new language subdirectory. For +example, all modules for German would be in /doc/reference/de/modules +and all illustrations in /doc/reference/de/images, note that you also have +to translate the master.xml in your language subdirectory. + +The initial translation is straightforward: Translate all modules and +all illustrations, but don't add any files, don't add any new XML elements +(like a section or a chapter, not even a paragraph). Simply translate +sentence by sentence. This is very important. + +Note that every DocBook XML file needs an encoding, specific to a +language. Add a line like this at the top of every file, if it doesn't exist: +<?xml version='1.0' encoding="iso-8859-1"?> + +You can use UTF-8 or any other character set, please experiment with +the builds to see what works for you. + +If you need a new section or paragraph, because your translation requires +more explanation, you can add it if you also add an "id" and a "revision" +to that new section or paragraph. + +For example, if you add a new <para> element to the existing document, +give it an identifier, a short unique string that extends the identifier +string of the parent element: <para id="queryhql-projection-specialnote"> +would be a special paragraph in the <sect1 id="queryhql-projection"> +section in the chapter <chapter id="queryhql">. + +Never add a new element in a translated version without also adding a new +unique identifier value! Also, you have to mark this new element as "only +relevant in the translated version". Simply set the "revision" attribute of +your new element to "-1". For example, set the previously created +paragraph to "only relevant in the translation" by declaring +<para id="queryhql-projection-specialnote" revision="-1">. +Changes to that paragraph will not be tracked, it is your responsibility to +watch out for neccessary updates. Any element with revision="-1" will not be +tracked. + + +5. Updating translated documentation + +Translators get updates by updating their working directory from the +repository. As a translator you will get an e-mail from us when translation +is required, you can then update your copy. Or, subscribe to the commit +mailing list to get all updates automatically. + +The documentation tools can generate a report after you updated +from the repository and show you what needs to be translated and/or removed +in your local translation copy. To generate that report, run "ant all.revdiff" +in the doc/reference/ subdirectory. Click on the generated HTML report +file for your language and you will see what has to be updated and/or +removed. + +If the report indicates that content in the original has been removed, +simply remove the identified XML element from your language modules. + +If the report detects a new revision, open the file that has been updated +in your translation, find the identified XML element and update/translate +its contents. Important: Make sure you also update the "revision" +attribute of that XML element by setting it to the same version as in +the original file, hence both the original XML file and your translated +file should have the same revision number for all elements. If an +XML element in your translation doesn't have a revision, but the original +file has, add a new "revision" attribute to your XML element. +The HTML report shows the identifiers and revisions for both the original +and the translated files, use it to compare. + +Rerun the "ant all.revdiff" report generation as often as you like until +no more differences are detected. You should always try to get your +copy clean, with all updated revisions and all identified elements +synchronzied. + + +6. Committing a translation + +All translators will be asked to submit their translated versions from +time to time. This will be a manual process, you will get an e-mail from +the Hibernate team and simply send your language subdirectory as +a ZIP file to us. It will then be integrated in the main Hibernate +distribution and on the website. Or, you can contact us for commit access +to the repository, where you can maintain a translation directly. + + +7. Generating PDF and HTML output + +The documentation is generated with the target 'ant all.doc'. + +To build the reference docs for a particular language only, use +"ant -Dlang=en", for example, and call either lang.all, lang.docpdf, +lang.dochtml, or lang.dochtmlsingle for the target of your choice. + +You can also call lang.section-check to track down missing identifiers in +a particular language, or you can call lang.revdiff to get a difference +report for a particular language, compared with the English reference. Property changes on: core/trunk/documentation/jbosscache2/README ___________________________________________________________________ Name: svn:executable + * Added: core/trunk/documentation/jbosscache2/pom.xml =================================================================== --- core/trunk/documentation/jbosscache2/pom.xml (rev 0) +++ core/trunk/documentation/jbosscache2/pom.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,86 @@ +<project xmlns="http://maven.apache.org/POM/4.0.0" + xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" + xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> + + <modelVersion>4.0.0</modelVersion> + + <parent> + <groupId>org.hibernate</groupId> + <artifactId>hibernate-core-parent</artifactId> + <version>1</version> + </parent> + + <groupId>org.hibernate</groupId> + <artifactId>hibernate-jbc2-manual</artifactId> + <version>3.3.0-SNAPSHOT</version> + <packaging>jdocbook</packaging> + + <name>Hibernate/JBoss Cache 2 Reference Manual</name> + <description>The Hibernate / JBoss Cache 2 integration reference manual</description> + + <build> + <plugins> + <plugin> + <groupId>org.jboss.maven.plugins</groupId> + <artifactId>maven-jdocbook-plugin</artifactId> + <version>2.1.0-SNAPSHOT</version> + <extensions>true</extensions> + <dependencies> + <dependency> + <groupId>org.hibernate</groupId> + <artifactId>hibernate-jdocbook-style</artifactId> + <version>1.0.1-SNAPSHOT</version> + <type>jdocbook-style</type> + </dependency> + </dependencies> + <configuration> + <sourceDocumentName>Hibernate_JBC2_Reference.xml</sourceDocumentName> + <masterTranslation>en-US</masterTranslation> + <translations> + <translation>es-ES</translation> + <translation>fr-FR</translation> + <translation>ja-JP</translation> + <translation>ko-KR</translation> + <translation>pt-BR</translation> + <translation>zh-CN</translation> + </translations> + <imageResource> + <directory>src/main/docbook/en-US</directory> + <excludes> + <exclude>*.xml</exclude> + <exclude>**/*.xml</exclude> + <exclude>*.zargo</exclude> + <exclude>**/*.zargo</exclude> + </excludes> + </imageResource> + <formats> + <format> + <formatName>pdf</formatName> + <stylesheetResource>classpath:/xslt/hibernate/pdf/main-pdf.xsl</stylesheetResource> + <finalName>hibernate_reference.pdf</finalName> + <profilingTypeName>two_pass</profilingTypeName> + </format> + <format> + <formatName>html_single</formatName> + <stylesheetResource>classpath:/xslt/hibernate/html/main-single.xsl</stylesheetResource> + <finalName>index.html</finalName> + <profilingTypeName>two_pass</profilingTypeName> + </format> + <format> + <formatName>html</formatName> + <stylesheetResource>classpath:/xslt/hibernate/html/main-chunk.xsl</stylesheetResource> + <finalName>index.html</finalName> + <profilingTypeName>two_pass</profilingTypeName> + </format> + </formats> + <options> + <xincludeSupported>true</xincludeSupported> + <localeSeparator>-</localeSeparator> + <useRelativeImageUris>true</useRelativeImageUris> + </options> + </configuration> + </plugin> + </plugins> + </build> + +</project> Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/Hibernate_JBC2_Reference.xml =================================================================== --- core/trunk/documentation/jbosscache2/src/main/docbook/en-US/Hibernate_JBC2_Reference.xml (rev 0) +++ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/Hibernate_JBC2_Reference.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,61 @@ +<?xml version='1.0' encoding="UTF-8"?> +<!-- + ~ Copyright (c) 2008, Red Hat Middleware, LLC. All rights reserved. + ~ + ~ This copyrighted material is made available to anyone wishing to use, modify, + ~ copy, or redistribute it subject to the terms and conditions of the GNU + ~ Lesser General Public License, v. 2.1. This program is distributed in the + ~ hope that it will be useful, but WITHOUT A WARRANTY; without even the implied + ~ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + ~ Lesser General Public License for more details. You should have received a + ~ copy of the GNU Lesser General Public License, v.2.1 along with this + ~ distribution; if not, write to the Free Software Foundation, Inc., + ~ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + ~ + ~ Red Hat Author(s): Brian Stansberry + --> +<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [ + <!ENTITY versionNumber "3.3.0.alpha1"> + <!ENTITY copyrightYear "2008"> + <!ENTITY copyrightHolder "Red Hat Middleware, LLC."> +]> + +<book> + + <bookinfo> + <title>HIBERNATE - Relational Persistence for Idiomatic Java</title> + <subtitle>Using JBoss Cache 2 as a Hibernate Second Level Cache</subtitle> + <releaseinfo>&versionNumber;</releaseinfo> + <productnumber>&versionNumber;</productnumber> + <issuenum>1</issuenum> + <mediaobject> + <imageobject role="fo"> + <imagedata fileref="images/hibernate_logo_a.png" align="center" /> + </imageobject> + <imageobject role="html"> + <imagedata fileref="images/hibernate_logo_a.png" depth="3cm" /> + </imageobject> + </mediaobject> + <copyright> + <year>&copyrightYear;</year> + <holder>&copyrightHolder;</holder> + </copyright> + <xi:include href="legal_notice.xml" xmlns:xi="http://www.w3.org/2001/XInclude" /> + <!-- include translators... --> + </bookinfo> + + <toc/> + + <xi:include href="content/preface.xml" xmlns:xi="http://www.w3.org/2001/XInclude" /> + + <xi:include href="content/introduction.xml" xmlns:xi="http://www.w3.org/2001/XInclude" /> + + <xi:include href="content/concepts.xml" xmlns:xi="http://www.w3.org/2001/XInclude" /> + + <xi:include href="content/configuration.xml" xmlns:xi="http://www.w3.org/2001/XInclude" /> + + <xi:include href="content/eviction.xml" xmlns:xi="http://www.w3.org/2001/XInclude" /> + + <xi:include href="content/architecture.xml" xmlns:xi="http://www.w3.org/2001/XInclude" /> +</book> + Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/architecture.xml =================================================================== --- core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/architecture.xml (rev 0) +++ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/architecture.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,293 @@ +<?xml version='1.0' encoding="UTF-8"?> +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> + +<!-- + ~ Copyright (c) 2008, Red Hat Middleware, LLC. All rights reserved. + ~ + ~ This copyrighted material is made available to anyone wishing to use, modify, + ~ copy, or redistribute it subject to the terms and conditions of the GNU + ~ Lesser General Public License, v. 2.1. This program is distributed in the + ~ hope that it will be useful, but WITHOUT A WARRANTY; without even the implied + ~ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + ~ Lesser General Public License for more details. You should have received a + ~ copy of the GNU Lesser General Public License, v.2.1 along with this + ~ distribution; if not, write to the Free Software Foundation, Inc., + ~ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + ~ + ~ Red Hat Author(s): Brian Stansberry + --> +<chapter id="architecture"> + + <title>Architecture</title> + + <para> + We've now gone through all the main concepts and the configuration + details; now we'll look a bit under the covers to understand a bit + more about the architectural design of the Hibernate/JBoss Cache + integration. Readers can skip this chapter if they aren't interested + in a look under the covers. + </para> + + <sect1 id="architecture-interface" revision="1"> + <title>Hibernate Interface to the Caching Subsystem</title> + + <para> + The rest of Hibernate interacts with the Second Level Cache subsystem + via the <literal>org.hibernate.cache.RegionFactory</literal> interface. + What implementation of the interface is used is determined by the + value of the <literal>hibernate.cache.region.factory_class</literal> + configuration property. The interface itself is straightforward: + </para> + + <programlisting><![CDATA[void start(Settings settings, Properties properties) + throws CacheException; + +void stop(); + +boolean isMinimalPutsEnabledByDefault(); + +long nextTimestamp(); + +EntityRegion buildEntityRegion(String regionName, + Properties properties, + CacheDataDescription metadata) + throws CacheException; + +CollectionRegion buildCollectionRegion(String regionName, + Properties properties, + CacheDataDescription cdd) + throws CacheException; + +QueryResultsRegion buildQueryResultsRegion(String regionName, + Properties properties) + throws CacheException; + +TimestampsRegion buildTimestampsRegion(String regionName, + Properties properties) + throws CacheException;]]></programlisting> + + <itemizedlist> + <listitem> + <para> + The <literal>start</literal> method is invoked during + <literal>SessionFactory</literal> startup and allows the region + factory implementation to access all the configuration settings + and initialize itself. The <literal>stop</literal> method is + invoked during <literal>SessionFactory</literal> shutdown. + </para> + </listitem> + <listitem> + <para> + The various <literal>build***Region</literal> methods are invoked as + Hibernate detects it needs to cache different data. Hibernate can + invoke these methods multiple times, with different + <literal>regionName</literal> values; each call results in the + establishment of a separate area in the underlying JBoss Cache + instance(s). For example, if an application includes an + entity class <literal>org.example.Order</literal> and another entity + class <literal>org.example.LineItem</literal>, you would see two + calls to <literal>buildEntityRegion</literal>, one for the + <literal>Order</literal> class and one for the + <literal>LineItem</literal> class. (Note that it is possible, and + recommended, to configure one or more shared regions for entities, + collections and queries. See <xref linkend="eviction-organization"/> + for some examples.) + </para> + </listitem> + <listitem> + <para> + For each call to a <literal>build***Region</literal> method, the + region factory returns a region object implementing the + <literal>EntityRegion</literal>, <literal>CollectionRegion</literal>, + <literal>QueryResultsRegion</literal> or <literal>TimestampsRegion</literal> + interface. Each interface specifies the needed semantics for + caching the relevant type of data. Thereafter, the Hibernate core + invokes on that region object to manage reading and writing data + in the cache. + </para> + </listitem> + </itemizedlist> + + <para> + Next, we'll look at the architecture of how the JBoss Cache integration + implements these interfaces, first in the case where a single JBoss + Cache instance is used, next in the case where multiple instances are + desired. + </para> + + </sect1> + + <sect1 id="architecture-single-cache" revision="1"> + <title>Single JBoss Cache Instance Architecture</title> + + <para> + The following diagram illustrates the key elements involved when + a single JBoss Cache instance is used: + </para> + + <mediaobject> + <imageobject role="fo"> + <imagedata fileref="images/single-cache.png" format="PNG" align="center" /> + </imageobject> + <imageobject role="html"> + <imagedata fileref="images/single-cache.png" format="PNG" align="center" /> + </imageobject> + </mediaobject> + + <itemizedlist> + <listitem> + <para> + For the single cache case, the user should specify + <literal>SharedJBossCacheRegionFactory</literal> as their + <literal>hibernate.cache.region.factory_class</literal>. + </para> + </listitem> + <listitem> + <para>As part of its startup process, te region factory delegates + responsibility for providing JBoss Cache instances to an + implementation of the + <literal>org.hibernate.cache.jbc2.CacheInstanceManager</literal> + interface. The region factory separately requests a JBoss Cache + instance for entities, one for collections, one for queries and one + for timestamps. Whether the <literal>CacheInstanceManager</literal> + provides the same underlying JBoss Cache instance for each + request or provides multiple caches is an implementation detail + of the <literal>CacheInstanceManager</literal>. + </para> + </listitem> + <listitem> + <para> + <literal>SharedJBossCacheRegionFactory</literal> creates an + instance of <literal>SharedCacheInstanceManager</literal> as + its <literal>CacheInstanceManager</literal>. + <literal>SharedCacheInstanceManager</literal> uses the JBoss Cache + configuration file specified by the user to create a single + <literal>org.jboss.cache.Cache</literal> instance, and provides + that same instance to the region factory when it requests the + cache for entities, collections, queries and timestamps. + <literal>SharedCacheInstanceManager</literal> also creates an + <literal>org.jgroups.ChannelFactory</literal> and passes it to + the <literal>Cache</literal>. The <literal>ChannelFactory</literal> + provides the cache with the <literal>org.jgroups.Channel</literal> + it uses for intra-cluster communication. + </para> + </listitem> + <listitem> + <para> + At this point, the region factory has a reference to a cache + for entities, a reference to a cache for collections, one for + queries and one for timestamps. In this particular case, each + reference points to the same underlying <literal>Cache</literal> + instance. When core Hibernate invokes the + <literal>buildEntityRegion</literal> operation on the region + factory, it instantiates an implementation of the + <literal>EntityRegion</literal> interface that knows how to + interface with JBoss Cache, passing it a reference to its + entity cache. Same thing happens for collections, etc. + </para> + </listitem> + <listitem> + <para> + Core Hibernate invokes on the <literal>EntityRegion</literal>, + which in turn invokes read and write operations on the underlying + JBoss Cache. The cache uses its <literal>Channel</literal> to + propagate changes to its peers in the cluster. + </para> + </listitem> + <listitem> + <para> + When the <literal>SessionFactory</literal> shuts down, it + invokes <literal>stop()</literal> on the region factory, which + in turn ensures that the JBoss Cache instance is stopped and + destroyed (which in turn closes the JGroups channel). + </para> + </listitem> + </itemizedlist> + </sect1> + + <sect1 id="architecture-cache-per-type" revision="1"> + <title>Multiple JBoss Cache Instance Architecture</title> + + <para> + The situation when multiple JBoss Cache instances are used is very + similar to the single cache case: + </para> + + <mediaobject> + <imageobject role="fo"> + <imagedata fileref="images/multi-cache.png" format="PNG" align="center" /> + </imageobject> + <imageobject role="html"> + <imagedata fileref="images/multi-cache.png" format="PNG" align="center" /> + </imageobject> + </mediaobject> + + <itemizedlist> + <listitem> + <para> + Here the user should specify + <literal>MultiplexedJBossCacheRegionFactory</literal> as their + <literal>hibernate.cache.region.factory_class</literal>. The + <literal>MultiplexedJBossCacheRegionFactory</literal> shares + almost all its code with <literal>SharedJBossCacheRegionFactory</literal>; + the main difference is it constructs a different <literal>CacheInstanceManager</literal> + implementation -- the <literal>MultiplexedCacheInstanceManager</literal>. + </para> + </listitem> + <listitem> + <para> + <literal>MultiplexedCacheInstanceManager</literal> differs from + <literal>SharedCacheInstanceManager</literal> in that it does + not directly instantiate a cache. Rather, it creates an + instance of <literal>org.jboss.cache.CacheManager</literal>, + providing it with a <literal>ChannelFactory</literal> and the + location of the user-specified cache configuration file. The + <literal>CacheManager</literal> parses the configuration file. + </para> + </listitem> + <listitem> + <para> + <literal>MultiplexedCacheInstanceManager</literal> analyzes + Hibernate's configuration to determine the name of the desired + cache configuration for entities, collections, queries and + timestamps. See <xref linkend="sessionfactory-multiplexed"/> for + details. It then asks its <literal>CacheManager</literal> to + provide each needed cache. In the diagram, two different caches are needed: + </para> + <itemizedlist> + <listitem> + <para>One, using the "optimistic-entity" configuration, + that is used for entities, collections and queries + </para> + </listitem> + </itemizedlist> + <itemizedlist> + <listitem> + <para>Another, with the "timestamps-cache" configuration, + that is used for timestamps. + </para> + </listitem> + </itemizedlist> + + <para> + Both the "optimistic-entity" configuration and the "timestamps-cache" + configuration specify the use of the "udp" JGroups channel + configuration, so the <literal>CacheManager</literal>'s + <literal>ChannelFactory</literal> will ensure that they share + the underlying JGroups resources. + </para> + </listitem> + <listitem> + <para> + The way the region factory creates regions is exactly the same + as in the single JBoss Cache case; the only difference is the + region factory's internal reference to its timestamps cache + now points to a different cache object from the entity, collection + and query cache references. + </para> + </listitem> + </itemizedlist> + + </sect1> + +</chapter> \ No newline at end of file Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/concepts.xml =================================================================== --- core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/concepts.xml (rev 0) +++ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/concepts.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,944 @@ +<?xml version='1.0' encoding="UTF-8"?> +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> + +<!-- + ~ Copyright (c) 2008, Red Hat Middleware, LLC. All rights reserved. + ~ + ~ This copyrighted material is made available to anyone wishing to use, modify, + ~ copy, or redistribute it subject to the terms and conditions of the GNU + ~ Lesser General Public License, v. 2.1. This program is distributed in the + ~ hope that it will be useful, but WITHOUT A WARRANTY; without even the implied + ~ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + ~ Lesser General Public License for more details. You should have received a + ~ copy of the GNU Lesser General Public License, v.2.1 along with this + ~ distribution; if not, write to the Free Software Foundation, Inc., + ~ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + ~ + ~ Red Hat Author(s): Brian Stansberry + --> +<chapter id="concepts"> + + <title>Core Concepts</title> + + <para> + This chapter focuses on some of the core concepts underlying how the + JBoss Cache-based implementation of the Hibernate Second Level Cache works. + There's a fair amount of detail, which certainly doesn't all need to be + mastered to use JBoss Cache with Hibernate. But, an understanding of some + of the basic concepts here will help a user understand what some of the + typical configurations discussed in the next chapter are all about. + </para> + + <para> + If you want to skip the details for now, feel free to jump ahead to + <xref linkend="concepts-cache-matching-process"/> + </para> + + <sect1 id="concepts-data-types" revision="1"> + <title>Types of Cached Data</title> + + <para> + The Second Level Cache can cache four different types of data: entities, + collections, query results and timestamps. Proper handling of each + of the types requires slightly different caching semantics. A major + improvement in Hibernate 3.3 is the addition of the + <literal>org.hibernate.cache.RegionFactory</literal> API, which + allows Hibernate to tell the caching integration layer what type + of data is being cached. Based on that knowledge, the cache integration + layer can apply the semantics appropriate to that type. + </para> + + <sect2 id="concepts-data-types-entity" revision="1"> + <title>Entities</title> + <para> + Entities are the most common type of data cached in the second level + cache. Entity caching requires the following semantics in a + clustered cache: + </para> + + <itemizedlist> + <listitem> + <para> + Newly created entities should only be stored on the node on + which they are created until the transaction in which they + were created commits. Until that transaction commits, the + cached entity should only be visible to that transaction. + After the transaction commits, cluster-wide the cache should + be in a "consistent" state. The cache is consistent if on + any node in the cluster, the new entity is either: + + <itemizedlist> + <listitem> + <para> + stored in the cache, with all non-collection fields + matching what is in the database. + </para> + </listitem> + <listitem> + <para> + not stored in the cache at all. + </para> + </listitem> + </itemizedlist> + </para> + + <para> + Maintaining cache consistency basically requires that the + cluster-wide update messages that inform other nodes of + the changes made during a transaction be made + <emphasis>synchronously</emphasis> as part of the transaction + commit process. This means that the transaction thread will + block until the changes have been transmitted to all nodes + in the cluster, those nodes have updated their internal + state to reflect the changes, and have responded to the + originating node telling them of their success (or failure) + in doing so. JBoss Cache uses a 2 phase commit protocol, so + there will actually be 2 synchronous cluster-wide messages per + transaction commit. If any node in the cluster fails in the + initial prepare phase of the 2PC, the underlying transaction + will be rolled back and in the second phase JBoss + Cache will tell the other nodes in the cluster to revert + the change. + </para> + </listitem> + + <listitem> + <para> + For existing entities that are modified in the course of a + transaction, the updated entity state should only be stored + on the node on which the modification occurred until the + transaction commits. Until that transaction commits, the + changed entity state should only be visible to that transaction. + After the transaction commits, cluster-wide the cache should + be in a "consistent" state, as described above. + </para> + <para> + Concurrent cache updates of the same entity anywhere in the + cluster should not be possible, as Hibernate will acquire + an exclusive lock on the database representation of the entity + before attempting to update the cache. + </para> + </listitem> + + <listitem> + <para> + A read of a cached entity holds a transaction scope read lock on + the relevant portion of cache. The presence of a read lock + held by one transaction should not prevent a concurrent read + by another transaction. Whether the presence of that read + lock prevents a concurrent write depends on whether the cache + is configured for READ_COMMITTED or REPEATABLE_READ semantics + and whether the cache is using optimistic locking. READ_COMMITTED + will allow a concurrent write to proceed; pessimistic locking + with REPEATABLE_READ will cause the write to block until the + transaction with the read lock commits. Optimistic locking + allows a REPEATABLE_READ semantic without forcing the writing + transaction to block. + </para> + + <para> + A read of a cached entity does not result in any messages to + other nodes in the cluster or any cluster-wide read locks. + </para> + + </listitem> + + <listitem> + <para> + The basic operation of storing an entity that has been directly + read from the database should have a <emphasis>fail-fast</emphasis> + semantic. This type of operation is referred to as a <emphasis>put</emphasis> + and is the most common type of operation. Basically, the + rules for handling new entities or entity updates discussed + above mean the cache's representation of an entity should + always match the database's. So, if a <literal>put</literal> + attempt encounters any existing copy of the entity in the cache, + it should assume that existing copy is either newer or the same + as what it is trying to store, and the <literal>put</literal> + attempt should promptly and silently abort, with no impact on + any ongoing transactions. + </para> + + <para> + A <literal>put</literal> operation should not acquire any + long-lasting locks on the cache. + </para> + + <para> + If the cache is configured to use replication, the replication + of the <literal>put</literal> should occur immediately, not + waiting for transaction commit and without the calling thread + needing to block waiting for responses from the other nodes + in the cluster. This is a "fire-and-forget" semantic that + JBoss Cache refers to as <emphasis>asynchronous replication</emphasis>. + When other nodes receive a replicated <literal>put</literal>, + they use the same fail-fast semantics as a local <literal>put</literal> + -- i.e. promptly and silently abort if the entity is already cached. + </para> + + <para> + If the cache is configured to use invalidation, a + <literal>put</literal> should not result in any cluster-wide + message at all. The fact that one node in the cluster has + cached an entity should not invalidate another node's cache + of that same entity -- both caches are storing the same + information. + </para> + + </listitem> + + <listitem> + <para> + A removal of an entity from the cache (i.e. to reflect a + DELETE from the underlying database) is basically a special + case of a modification; the removal should not be visible on + other nodes or to other transactions until the transaction that + did the remove commits. Cache consistency after commit means the + removed entity is no longer in the cache on any node in the + cluster. + </para> + </listitem> + </itemizedlist> + </sect2> + + <sect2 id="concepts-data-types-collection" revision="1"> + <title>Collections</title> + <para> + Collection caching refers to the case where a cached entity has as + one of its fields a collection of other entities. Hibernate handles + this field specially in the second level cache; a special area in + the cache is created where the primary keys of the entities in the + collection are stored. + </para> + + <para> + The management of collection caching is very similar to entity + caching, with a few differences: + + <itemizedlist> + <listitem> + <para> + When a new entity is created that includes a collection, + no attempt is made to insert the collection into the cache. + </para> + </listitem> + <listitem> + <para> + When a transaction updates the contents of a collection, + no attempt is made to reflect the new contents of the collection + in the cache. Instead, the existing collection is simply + removed from the cache across the cluster, using the same + semantics as an entity removal. + </para> + </listitem> + </itemizedlist> + </para> + + <para> + In essence, for collections Hibernate only supports cache reads and + the <literal>put</literal> operation, with any modification of the + collection resulting in cluster-wide invalidation of that collection + from the cache. If the collection field is accessed again, a new read from + the database will be done, followed by another cache <literal>put</literal>. + </para> + </sect2> + + <sect2 id="concepts-data-types-queries" revision="1"> + <title>Queries</title> + + <para> + Hibernate supports caching of query results in the second level + cache. The HQL statement that comprised the query is cached (including + any parameter values) along with the primary keys of all entities + that comprise the result set. + </para> + + <para> + The semantics of query caching are significantly different + from those of entity caching. A database row that reflects an + entity's state can be locked, with cache updates applied with that + lock in place. The semantics of entity caching take advantage of + this fact to help ensure cache consistency across the cluster. + There is no clear database analogue to a query result set that can + be efficiently locked to ensure consistency in the cache. As a result, + the fail-fast semantics used with the entity caching <literal>put</literal> + operation are not available; instead query caching has semantics + akin to an entity insert, including costly synchronous cluster + updates and the JBoss Cache two phase commit protocol. Furthermore, + Hibernate must agressively invalidate query results from the cache + any time any instance of one of the entity classes involved in the + query's WHERE clause changes. All such query results are invalidated, + even if the change made to the entity instance would not have affected + the query result. It is not performant for Hibernate to try to + determine if the entity change would have affected the query result, + so the safe choice is to invaldiate the query. See + <xref linkend="concepts-data-types-timestamps"/> for more on query + invalidation. + </para> + + <para> + The effect of all this is that query caching is less likely to + provide a performance boost than entity/collection caching. Use it + with care and benchmark your application with it enabled and disabled. + Be careful about replicating query results; caching them locally + only on the node that executed the query will be more + performant unless the query is quite expensive, is very likely to + be repeated on other nodes, and is unlikely to be invalidated out + of the cache.<footnote><para>See the discussion of the + <literal>hibernate.cache.region.jbc2.query.localonly</literal> + property in <xref linkend="sessionfactory"/></para> for more on how + to only cache query results locally.</footnote>. + </para> + + <para> + The JBoss Cache-based implementation of query caching adds a couple + of interesting semantics, both designed to ensure that query + cache operations don't block transactions from proceeding: + + <itemizedlist> + <listitem> + <para> + The insertion of a query result into the cache is very much + like the insertion of a new entity. The difference is it + is possible for two transactions, possibly on different + nodes, to try to insert the same query at the same time. + (If this happened with entities, the database would throw + an exception with a primary key violation before any + caching work could start). This could lead to long delays + as the transactions compete for cache locks. To prevent + such delays, the cache integration layer will set a very + short (a few ms) lock timeout before attempting to cache a + query result. If there is any sort of locking conflict, + it will be detected quickly, and the attempt to cache the + result will be quietly abandonded. + </para> + </listitem> + <listitem> + <para> + A read of a query result does not result in any long-lasting + read lock in the cache. Thus, the fact that an uncommitted + transaction had read a query result does not prevent concurrent + transactions from subsequently invalidating that result and + caching a new result set. However, an insertion of a query result + into the cache will result in an exclusive write lock that + lasts until the transaction that did the insert commits; this + lock will prevent other transactions from reading the result. + Since the point of query caching is to improve performance, + blocking on a cache read for an extended period seems + suboptimal. So, the cache integration code will set a very + low lock acquisition timeout before attempting the read; if + there is a lock conflict, the read will silently fail, + resulting in a cache miss and a re-execution of the query + against the database. + </para> + </listitem> + </itemizedlist> + </para> + + </sect2> + + <sect2 id="concepts-data-types-timestamps" revision="1"> + <title>Timestamps</title> + + <para> + Timestamp caching is an internal detail of query caching. As part of + each query result, Hibernate stores the timestamp of when the query + was executed. There is also a special area in the cache (the + <emphasis>timestamps cache</emphasis>) where, for each entity class, + the timestamp of the last update to any instance of that class is + stored. When a query result is read from the cache, its timestamp + is compared to the timestamps of all entities involved in the query. + If any entity has a later timestamp, the cached result is discarded + and a new query against the database is executed. + </para> + + <para> + The semantics of of the timestamp cache are quite different from + those of the entity, collection and query caches. + + <itemizedlist> + <listitem> + <para> + For all nodes in the cluster, the contents of the timestamp + cache should be identical, with all timestamps represented. + For the other cache types, it is acceptable for some nodes + in the cluster to not store some data, as long as everyone + who does store an item stores the same thing. Not so with + timestamps -- everyone must store all timestamps. Using a + JBoss Cache configured for invalidation is not allowed for + the timestamps cache. Further, configuring JBoss Cache + eviction to remove old or infrequently used data from the + timestamps cache should not be done. Also, when a new node + joins a running cluster, it must acquire the current state of all + timestamps from another member, performing what is known as an + <emphasis>initial state transfer</emphasis>. + For other cache types, an initial state transfer is not + required. + </para> + </listitem> + <listitem> + <para> + A timestamp represents an entire entity class, not a single + instance. Thus it is quite likely that two concurrent + transactions will both attempt to update the same timestamp. + These updates need to be serialized, but no long lasting + exclusive lock on the timestamp is held. + </para> + </listitem> + <listitem> + <para> + As soon as a timestamp is updated, the new value needs to be + propagated around the cluster. Waiting until the transaction + that changed the timestamp commits is inadequate. So, changes + to timestamps can be quite "chatty" in terms of how many + messages are sent around the cluster. Sending the timestamp + update messages synchronously would have a serious impact + on performance, and would quite likely result in + cluster-wide lock conflicts that would prevent transactions + from progressing for tens of seconds at a time. To mitigate + these issues, timestamp updates are sent asynchronously. + </para> + </listitem> + </itemizedlist> + </para> + + </sect2> + </sect1> + + <sect1 id="concepts-cache-attributes" revision="1"> + <title>Key JBoss Cache Behaviors</title> + + <para> + JBoss Cache is a very flexible tool and includes a great number of + configuration options. See the <emphasis>JBoss Cache User Guide</emphasis> + for an in depth discussion of these options. Here we focus on the + main concepts that are most important to the Second Level Cache use case. + This discussion will focus on concepts; see <xref linkend="jbc-config"/> for + details on the actual configurations involved. + </para> + + <sect2 id="concepts-cache-attr-repl" revision="1"> + <title>Replication vs. Invalidation vs. Local Mode</title> + + <para> + JBoss Cache provides three different choices for how a node in the + cluster should interact with the rest of the cluster when its local + state is updated: + + <itemizedlist> + <listitem> + <para> + <emphasis>Replication:</emphasis> The updated cache will + send its new state (e.g. the new values for an entity's fields) + to the other members of the cluster. This is heavy in terms + of the size of network traffic, since the new state needs to + be transmitted. It also has the effect forcing the data that + is cached in each node in the cluster to be the same, even if + the users accessing the various nodes are interested in + different data. So, if a user on node A reads an + <literal>Order</literal> entity with primary + key <literal>12343439485030</literal> from the database, + with replication that entity will be cached on every node + in the cluster, even though no other users are interested + in that particular <literal>Order</literal>. + </para> + + <para> + Because of these downsides, replication is generally not the + best choice for entity, collection and query caching. + However, in a cluster <emphasis>replication is the only + valid choice for the timestamps cache</emphasis>. + </para> + + </listitem> + + <listitem> + <para> + <emphasis>Invalidation:</emphasis> The updated cache will + send a message to the other members of the cluster telling + them that a particular piece of data (e.g. a particular entity) + has been modified. Upon receipt of this message, the other + nodes will remove this data from their local cache, if it + is stored there. Invalidation is lighter than replication + in terms of network traffic, since only the "id" of the + data needs to be transmitted, not the entire new state. + The downside to invalidation is that if the invalidated + data is needed again, it has to be re-read from the database. + However, in most cases data that many nodes in the cluster + all want to have in memory is not data that is frequently + changed. + </para> + + <para> + Invalidation makes no sense for query caching; if it is + used for a query cache region the Hibernate/JBoss Cache + integration will detect this and switch any query cache + related calls to Local mode. Invalidation must not be used + for timestamp caching; Hibernate will throw an exception + during session factory startup if it finds that it is. + </para> + + </listitem> + + <listitem> + <para> + <emphasis>Local:</emphasis> The updated cache does not even + know if there are any other nodes, and will not attempt + to update them. If JBoss Cache is used as a Second + Level Cache in a non-clustered environment, Local mode + should be used. <emphasis>If there is a cluster, Local + mode should never be used for entity, collection or + timestamp caching.</emphasis> Local mode can be used + for query caching in a cluster, since the replicated + timestamps cache will ensure that outdated cached queries + are not used. Often Local mode is the best choice for + query caching, as query results can be large and the cost + of replicating them high. + </para> + + <para> + If the same underlying JBoss Cache instance is used for + the query cache and any of the other caches, the + <literal>SessionFactory</literal> can be configured to suppress + replication of the queries, essentially making the queries + operate in Local mode. This is done by adding the following + configuration: + </para> + + <programlisting><![CDATA[hibernate.cache.region.jbc2.query.localonly=true]]></programlisting> + + <para> + If the JBoss Cache instance that the query cache is using + is configured for invalidation, setting this property isn't + even necessary; the Hibernate/JBoss Cache integration will + detect this condition and switch any query cache-related + calls to Local mode. + </para> + + </listitem> + </itemizedlist> + </para> + </sect2> + + <sect2 id="concepts-cache-attr-sync" revision="1"> + <title>Synchronous vs. Asynchronous</title> + + <para> + In JBoss Cache terms, <emphasis>synchronous</emphasis> vs. + <emphasis>asynchronous</emphasis> refers to whether a thread that + initiates a cluster-wide message blocks until that message has been + received, processed and acknowledged by the other members of the + cluster. Synchronous means the thread blocks; asynchronous means + the message is sent and the thread immediately returns; more of a + "fire and forget". An example of a message would be a set of cache + inserts, updates and removes sent out to the cluster as part of a + transaction commit. + </para> + + <para> + In almost all cases, the cache should be configured to use synchronous + messages, as these are the only way to ensure data consistency + across the cluster. JBoss Cache supports programatically overriding + the default configured behavior on a per-call basis, so for the + special cases where sending a message asynchronously is appropriate, + the Hibernate/JBoss Cache integration code will force the call + to go asynchronously. So, configure your caches to use + synchronous messages. + </para> + + </sect2> + + <sect2 id="concepts-cache-attr-lock" revision="1"> + <title>Locking Scheme</title> + + <para> + JBoss Cache supports both optimistic and pessimistic locking schemes. + See the <emphasis>JBoss Cache User Guide</emphasis> for an in depth + discussion of these options. In the Second Level Cache use case, the + main benefit of optimistic locking is that updates of cached entities + by one transaction do not block reads of the cached entity by other + transactions, yet REPEATABLE_READ semantics are preserved. Optimistic + locking has a higher level of runtime overhead, however. + </para> + + <para> + If you are using optimistic locking and data versioning in Hibernate + for your entities, you should use it in the entity cache as well. + </para> + + </sect2> + + <sect2 id="concepts-cache-attr-state" revision="1"> + <title>Initial State Transfer</title> + + <para> + When a new node joins a running cluster, it can request from an + existing member a copy of that member's current cache contents. + This process is known as an <emphasis>initial state transfer</emphasis>. + Doing an initial state transfer allows the new member to have a + "hot cache"; i.e. as user requests come in, data will already be + cached, helping avoid an initial set of reads from the database. + </para> + + <para> + However, doing an initial state transfer comes at a cost. The node + providing the state needs to lock its entire tree, serialize it and + send it over the network. This could be a large amount of data and + the transfer could take a considerable period of time to process. + While the transfer is ongoing, the state provider is holding locks + on its cache, preventing any local or replicated updates from + proceeeding. All work around the cache can come to a halt for a period. + </para> + + <para> + Because of this cost, we generally recommend avoiding initial state + transfers in the second level cache use case. The exception to this + is the timestamps cache. <emphasis>For the timestamps cache, an + initial state transfer is required.</emphasis> + </para> + + </sect2> + + <sect2 id="concepts-cache-attr-eviction" revision="1"> + <title>Cache Eviction</title> + + <para> + <emphasis>Eviction</emphasis> refers to the process by which old, + relatively unused, or excessively voluminous data can be dropped + from the cache, allowing the cache to remain within a memory budget. + Generally, applications that use the Second Level Cache should + configure eviction. See <xref linkend="eviction"/> for details. + </para> + </sect2> + + <sect2 id="concepts-cache-attr-misc" revision="1"> + <title>Buddy Replication and Cache Loading</title> + + <para> + <emphasis>Buddy replication</emphasis> refers to a JBoss Cache feature + whereby each node in the cluster replicates its cached data to a + limited number (often one) of "buddies" rather than to all nodes + in the cluster. <emphasis>Buddy replication should not be used in a + Second Level Cache</emphasis>. It is intended for use cases where + one node in the cluster "owns" some data , and just wants to make a + backup copy of the data to provide high availability. The data + (e.g. a web session) is never meant to be accessed simultaneously on + two different nodes in the cluster. Second Level Cache data does + not meet this "ownership" criteria; entities are meant to be + simultaneously usable by all nodes in the cluster. + </para> + + <para> + <emphasis>Cache Loading</emphasis> refers to a JBoss Cache feature + whereby cached data can be persisted to disk. The persisted data + either serves as a highly available copy of the data in case of + a cluster restart, or as an overflow area for when the amount of + cached data exceeds an application's memory budget. <emphasis>Cache + loading should not be used in a Second Level Cache</emphasis>. + The underlying database from which the cached data comes already + serves the same functions; adding a cache loader to the mix is + just wasteful. + </para> + </sect2> + + </sect1> + + <sect1 id="concepts-cache-matching" revision="1"> + <title>Matching JBC Behavior to Types of Data</title> + + <para> + The preceding discussion has gone into a lot of detail about what + Hibernate wants to accomplish as it caches data, and what JBoss Cache + configuration options are available. What should be clear is that the + configurations that are best for caching one type of data are not + the best (and are sometimes completely incorrect) for other types. + Entities likely work best with synchronous invalidation; timestamps + <emphasis>require</emphasis> replication; query caching might do + best in local mode. + </para> + + <para> + Prior to Hibernate 3.3 and JBoss Cache 2.1, the conflicting requirements + between the different cache types led to a real dilemna, particularly + if query caching was enabled. This conflict arose because all four + cache types needed to share a single underlying cache, with a single + configuration. If query caching was enabled, the requirements of the + timestamps cache basically forced use of synchronous replication, + which is the worst performing choice for the more critical + entity cache and is often inappropriate for the query cache. + </para> + + <para> + With Hibernate 3.3 and JBoss Cache 2.1 it has become + possible, even easy, to use separate underlying JBoss Cache instances + for the different cache types. As a result, the entity cache can be + optimally configured for entities while the necessary configuration + for the timestamps cache is maintained. + </para> + + <para> + There were three key changes that make this improvement possible: + </para> + + <sect2 id="concepts-cache-matching-region-factory" revision="1"> + <title>The <literal>RegionFactory</literal> Interface</title> + + <para> + As mentioned previously, Hibernate 3.3 introduced the + <literal>RegionFactory</literal> API as its mechanism for managing + the Second Level Cache. This API makes it possible for implementations + to know at all times whether they are working with entities, + collections, queries or timestamps. That knowledge allows the + Hibernate/JBoss Cache integration layer to make the best use of the + various options JBoss Cache provides. + </para> + + <para> + A Hibernate user doesn't need to understand the <literal>RegionFactory</literal> + API in any detail at all; the main point is internally it makes + possible independent management of the different cache types. + </para> + </sect2> + + <sect2 id="concepts-cache-matching-cache-manager" revision="1"> + <title>The <literal>CacheManager</literal> API</title> + + <para> + The <literal>CacheManager</literal> API is a new feature of JBoss + Cache 2.1. It provides an API for managing multiple distinct + JBoss Cache instances in the same VM. Basically a + <literal>CacheManager</literal> is instantiated and provided a set + of <emphasis>named</emphasis> cache configurations. An application + like the Hibernate/JBoss Cache integration layer accesses the + <literal>CacheManager</literal> and asks for a cache configured with + a particular named configuration. + </para> + + <para> + Again,a Hibernate user doesn't need to understand the + <literal>CacheManager</literal>; it's an internal detail. The thing + to understand is that the task of a Hibernate Second Level Cache user + is to: + + <itemizedlist> + <listitem> + <para> + Provide a set of named JBoss Cache configurations in an XML + file (or just use the default set included in the + <literal>jbc2-configs.xml</literal> file found in the + <literal>org.hibernate.cache.jbc2.builder</literal> package + in <literal>hibernate-jbosscache2.jar</literal>). + </para> + </listitem> + <listitem> + <para> + Tell Hibernate which cache configurations to use for entity, + collection, query and timestamp caching. In practice, this + can be quite simple, as there is a reasonable set of defaults. + </para> + </listitem> + </itemizedlist> + + </para> + + <para> + See <xref linkend="configuration"/> for more on how to do this. + </para> + + </sect2> + + <sect2 id="concepts-cache-matching-jgroups" revision="1"> + <title>Sharable JGroups Resources</title> + + <para> + JGroups is the group communication library JBoss Cache uses to send + messages around a cluster. Each cache has a JGroups + <literal>Channel</literal>; different channels + around the cluster that have the same name and compatible + configurations detect each other and form a group for message + transmission. + </para> + + <para> + A <literal>Channel</literal> is a fairly heavy object, typically + using a good number of threads, several sockets and some good sized + network I/O buffers. Creating multiple different channels in the + same VM was therefore costly, and was an administrative burden as + well, since each channel would need separate configuration to use + different network addresses or ports. Architecturally, this + mitigated against having multiple JBoss Cache instances in an + application, since each would need its own <literal>Channel</literal>. + </para> + + <para> + Added in JGroups 2.5 and much improved in the JGroups 2.6 + series is the concept of sharable JGroups resources. Basically, + the heavyweight JGroups elements can be shared. An application + (e.g. the Hibernate/JBoss Cache integration layer) uses a JGroups + <literal>ChannelFactory</literal>. The <literal>ChannelFactory</literal> + is provided with a set of <emphasis>named</emphasis> channel + configurations. When a <literal>Channel</literal> is needed (e.g. + by a JBoss Cache instance), the application asks the + <literal>ChannelFactory</literal> for the channel by name. If + different callers ask for a channel with the same name, the + <literal>ChannelFactory</literal> ensures that they get + channels that share resources. + </para> + + <para> + The effect of all this is that if a user wants to use four separate + JBoss Cache instances, one for entity caching, one for collection + caching, one for query caching and one for timestamp caching, those + four caches can all share the same underlying JGroups resources. + </para> + + <para> + The task of a Hibernate Second Level Cache user is to: + </para> + + <itemizedlist> + <listitem> + <para> + Provide a set of named JGroups configurations in an XML file + (or just use the default set included in the + <literal>jgroups-stacks.xml</literal> file found in the + <literal>org.hibernate.cache.jbc2.builder</literal> package + in the <literal>hibernate-jbosscache2.jar</literal>). + </para> + </listitem> + <listitem> + <para> + Tell Hibernate where to find that set of configurations + on the classpath. See <xref linkend="sessionfactory"/> for + details on how to do this. This is not necessary if the + default set included in <literal>hibernate-jbosscache2.jar</literal> + is used. + </para> + </listitem> + <listitem> + <para> + In the JBoss Cache configurations you are using specify + the name of the channel you want to use. This should be + one of the named configurations in the JGroups XML file. + The default set of JBoss Cache configurations found in the + <literal>hibernate-jbosscache2.jar</literal> already have + appropriate default choices. See <xref linkend="jbc-config-jgroups"/> + for details on how to set this if you don't wish to use the + defaults. + </para> + </listitem> + </itemizedlist> + + <para> + See <xref linkend="jgroups-config"/> for more on JGroups. + </para> + + </sect2> + + <sect2 id="concepts-cache-matching-process" revision="1"> + <title>Bringing It All Together</title> + + <para> + So, we've seen that Hibernate caches up to four different types of + data (entities, collections, queries and timestamps) and that + Hibernate 3.3 + JBoss Cache 2 gives you the flexibility to use a + separate underlying JBoss Cache, with different behavior, for each + type. You can actually deploy four separate caches, one for each type. + </para> + + <para> + In practice, four separate caches are unnecessary. For example, + entities and collection caching have similar enough semantics that + there is no reason not to share a JBoss Cache instance between them. + The queries can usually use the same cache as well. Similarly, + queries and timestamps can share a JBoss Cache instance configured + for replication, with the + <literal>hibernate.cache.region.jbc2.query.localonly=true</literal> + configuration letting you turn off replication for the queries if + you want to. + </para> + + <para> + Here's a decision tree you can follow: + + <orderedlist> + <listitem> + <para> + Decide if you want to enable query caching. + </para> + </listitem> + + <listitem> + <para> + Decide if you want to use invalidation or replication for + your entities and collections. Invalidation is generally + recommended for entities and collections. + </para> + <itemizedlist> + <listitem> + <para> + If you want invalidation, and you want query + caching, you will need two JBoss Cache instances, one + with synchronous invalidation for the entities and collections, + and one with synchronous replication for the timestamps. + The queries will go in the timestamp cache if you want them + to replicate; they can go with the entities and collections + otherwise. + </para> + </listitem> + <listitem> + <para> + If you want invalidation but don't want query caching, you can + use a single JBoss Cache instance, configured for synchronous + invalidation. + </para> + </listitem> + <listitem> + <para> + If you want replication, whether or not you want query caching, + you can use a single JBoss Cache instance, configured for + synchronous replication. + </para> + </listitem> + </itemizedlist> + </listitem> + + <listitem> + <para> + If you are using query caching, from the above decision tree + you've either got your timestamps sharing a cache with other + data types, or they are by themselves. Either way, + the cache being used for timestamps <emphasis>must have + initial state transfer enabled</emphasis>. Now, if the timestamps + are sharing a cache with entities, collections or queries, + decide whether you want initial state transfer for that other + data. See <xref linkend="concepts-cache-attr-state"/> + for the implications of this. If you don't want initial state + transfer for the other data, you'll need to have a separate + cache for the timestamps. + </para> + </listitem> + + <listitem> + <para> + Finally, if your queries are sharing a cache configured + for replication, decide if you want the cached query results + to replicate. (The timestamps cache <emphasis>must</emphasis> + replicate.) If not, you'll want to set the + <literal>hibernate.cache.region.jbc2.query.localonly=true</literal> + option when you configure your <literal>SessionFactory</literal> + </para> + </listitem> + </orderedlist> + + </para> + + <para> + Once you've made these decisions, you know whether you need just one + underlying JBoss Cache instance, or more than one. + Next we'll see how to actually configure the setup you've selected. + </para> + </sect2> + </sect1> + +</chapter> \ No newline at end of file Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/configuration.xml =================================================================== --- core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/configuration.xml (rev 0) +++ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/configuration.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,1052 @@ +<?xml version='1.0' encoding="UTF-8"?> +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> + +<!-- + ~ Copyright (c) 2008, Red Hat Middleware, LLC. All rights reserved. + ~ + ~ This copyrighted material is made available to anyone wishing to use, modify, + ~ copy, or redistribute it subject to the terms and conditions of the GNU + ~ Lesser General Public License, v. 2.1. This program is distributed in the + ~ hope that it will be useful, but WITHOUT A WARRANTY; without even the implied + ~ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + ~ Lesser General Public License for more details. You should have received a + ~ copy of the GNU Lesser General Public License, v.2.1 along with this + ~ distribution; if not, write to the Free Software Foundation, Inc., + ~ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + ~ + ~ Red Hat Author(s): Brian Stansberry + --> +<chapter id="configuration"> + + <title>Configuration</title> + + <para> + There are three main areas of configuration involved in using JBoss Cache + 2 for your Hibernate Second Level Cache: configuring the Hibernate + <literal>SessionFactory</literal>, configuring the underlying JBoss Cache + instance(s), and configuring the JGroups <literal>ChannelFactory</literal>. + If you use the standard JBoss Cache and JGroups configurations that ship + with the <literal>hibernate-jbosscache2.jar</literal>, then all you + need to worry about is the <literal>SessionFactory</literal> configuration. + </para> + + <sect1 id="sessionfactory" revision="1"> + <title>Configuring the Hibernate Session Factory</title> + + <sect2 id="sessionfactory-overview" revision="1"> + <title>Basics</title> + + <para> + There are four basic steps to configuring the + <literal>SessionFactory</literal>: + + <itemizedlist> + <listitem> + <para> + Tell Hibernate you whether to enable caching of entities and + collections. No need to set this property if you don't: + </para> + + <programlisting><![CDATA[hibernate.cache.use_second_level_cache=true]]></programlisting> + + </listitem> + + <listitem> + <para> + Tell Hibernate you want to enable caching of + query results. No need to set this property if you don't: + </para> + + <programlisting><![CDATA[hibernate.cache.use_query_cache=true]]></programlisting> + </listitem> + + <listitem> + <para> + If you have enabled caching of query results, tell Hibernate if + you want to suppress costly replication of those results around + the cluster. No need to set this property if you want query + results replicated: + </para> + + <programlisting><![CDATA[hibernate.cache.region.jbc2.query.localonly=true]]></programlisting> + </listitem> + + <listitem> + <para> + Finally, you need to tell Hibernate what <literal>RegionFactory</literal> + implementation to use to manage your caches. You do this by + setting the <literal>hibernate.cache.region.factory_class</literal> + configuration option. + </para> + + <programlisting><![CDATA[hibernate.cache.region.factory_class= + org.hibernate.cache.jbc2.MultiplexedJBossCacheRegionFactory]]></programlisting> + + <para> + To determine the correct factory class, you must decide + whether you need just one underlying JBoss + Cache instance to support the different types of caching + you will be doing, or whether you need more than one. See + <xref linkend="concepts"/> and particularly + <xref linkend="concepts-cache-matching-process"/> for more + on how to make that decision. Once you know the answer, + see <xref linkend="sessionfactory-factories"/> to find the + factory class that best meets your needs. + </para> + + <para> + Once you've specified your factory class, there may be + other factory-class-specific configurations you may + want to set. The available options are explained below. + </para> + </listitem> + + </itemizedlist> + + </para> + + + </sect2> + + <sect2 id="sessionfactory-factories" revision="1"> + <title>Specifying the <literal>RegionFactory</literal> Implementation</title> + + <para> + Hibernate 3.3 ships with the following <literal>RegionFactory</literal> + implementations that work with JBoss Cache 2. Select the + one that is appropriate to your needs and use it with + the <literal>hibernate.cache.region.factory_class</literal> + configuration option. + </para> + + <variablelist> + <varlistentry> + <term><literal>org.hibernate.cache.jbc2.SharedJBossCacheRegionFactory</literal></term> + <listitem> + <para> + Instantiates a single JBoss Cache instance for use with all + cache data types (entities, collections, queries, timestamps). + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>org.hibernate.cache.jbc2.JndiSharedJBossCacheRegionFactory</literal></term> + <listitem> + <para> + Uses a single JBoss Cache instance for all cache data types. + However, does not instantiate the JBoss Cache instance itself; + instead looks for an existing cache in JNDI. This allows + sharing of a single JBoss Cache instance across multiple + Hibernate session factories running in the same environment. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>org.hibernate.cache.jbc2.MultiplexedJBossCacheRegionFactory</literal></term> + <listitem> + <para> + Supports using multiple JBoss Cache instances with different + cache data types (entities, collections, queries, timestamps) + assigned to different JBoss Cache instances. Instantiates a + JBoss Cache <literal>CacheManager</literal> to manage the + JBoss Cache instances. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>org.hibernate.cache.jbc2.JndiMultiplexedJBossCacheRegionFactory</literal></term> + <listitem> + <para> + Functions like <literal>JndiMultiplexedJBossCacheRegionFactory</literal>, + but instead of instantiating its own <literal>CacheManager</literal> + it looks for an existing one in JNDI. This allows + sharing of the various JBoss Cache instances across multiple + Hibernate session factories running in the same environment. + </para> + </listitem> + </varlistentry> + </variablelist> + + </sect2> + + <sect2 id="sessionfactory-shared" revision="1"> + <title>The <literal>SharedJBossCacheRegionFactory</literal></title> + + <para> + The <literal>SharedJBossCacheRegionFactory</literal> supports a + number of additional configuration options: + </para> + + <variablelist> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cfg.shared</literal></term> + <listitem> + <para> + Classpath or filesystem resource containing JBoss Cache + configuration settings the underlying cache should use. + Default value is <literal>treecache.xml</literal>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cfg.multiplexer.stacks</literal></term> + <listitem> + <para> + Classpath or filesystem resource containing JGroups protocol + stack configurations the <literal>ChannelFactory</literal> + should use. Default is + <literal>org/hibernate/cache/jbc2/builder/jgroups-stacks.xml</literal>, + a file found in the <literal>hibernate-jbosscache2.jar</literal>. + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + Note that the default <literal>treecache.xml</literal> file does + not exist; it is up to the user to provide it. + </para> + </sect2> + + <sect2 id="sessionfactory-shared-jndi" revision="1"> + <title>The <literal>JndiSharedJBossCacheRegionFactory</literal></title> + + <para> + The <literal>JndiSharedJBossCacheRegionFactory</literal> supports an + additional configuration option: + </para> + + <variablelist> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cfg.shared</literal></term> + <listitem> + <para> + Specifies the JNDI name under which the JBoss Cache instance + to use is bound. Note that although this configuration property + has the same name as the one used by <literal>SharedCacheInstanceManager</literal>, + the meaning here is different. Note also that in this class' + usage of the property, there is no default value -- the user + must specify the property. + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + The <literal>JndiSharedJBossCacheRegionFactory</literal> requires + that the JBoss Cache instance is already bound in JNDI; it will + not create and bind one if it isn't. It is up to the the user + to ensure the cache is created and bound in JNDI before the + Hibernate <literal>SessionFactory</literal> is created. + </para> + + </sect2> + + <sect2 id="sessionfactory-multiplexed" revision="1"> + <title>The <literal>MultiplexedJBossCacheRegionFactory</literal></title> + + <para> + The <literal>MultiplexedJBossCacheRegionFactory</literal> supports a + number of additional configuration options: + </para> + + <variablelist> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.configs</literal></term> + <listitem> + <para> + Classpath or filesystem resource containing JBoss Cache + configurations the <literal>CacheManager</literal> should + use. Default is + <literal>org/hibernate/cache/jbc2/builder/jbc2-configs.xml</literal>, + a file found in the <literal>hibernate-jbosscache2.jar</literal>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cfg.multiplexer.stacks</literal></term> + <listitem> + <para> + Classpath or filesystem resource containing JGroups protocol + stack configurations the <literal>ChannelFactory</literal> + should use. Default is + <literal>org/hibernate/cache/jbc2/builder/jgroups-stacks.xml</literal>, + a file found in the <literal>hibernate-jbosscache2.jar</literal>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cfg.entity</literal></term> + <listitem> + <para> + Name of the configuration that should be used for entity caches. + Default value is <literal>optimistic-entity</literal>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cfg.collection</literal></term> + <listitem> + <para> + Name of the configuration that should be used for collection caches. + No default value, as by default we try to use the same JBoss Cache + instance that is used for entity caching. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cfg.ts</literal></term> + <listitem> + <para> + Name of the configuration that should be used for timestamp caches. + Default value is <literal>timestamps-cache</literal>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cfg.query</literal></term> + <listitem> + <para> + Name of the configuration that should be used for query caches. + By default, tries to use the same cache as is used for + entity caching. If there is no entity cache or it uses + invalidation, the default value is <literal>local-query</literal>. + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + Many of the default values name JBoss Cache configurations in the + standard <literal>jbc2-configs.xml</literal> file found in the + <literal>hibernate-jbosscache2.jar</literal>. See + <xref linkend="jbc-config-multiple-std"/> for details on those + configurations. If you want to set + <literal>hibernate.cache.region.jbc2.configs</literal> and use your + own JBoss Cache configuration file, you can still take advantage of + these defaults names; just name the configurations in your file + to match. + </para> + + <para> + This is all looks a bit complex, so let's show what happens if you + just configure the defaults, with query caching enabled: + </para> + + <programlisting><![CDATA[hibernate.cache.use_second_level_cache=true +hibernate.cache.use_query_cache=true +hibernate.cache.region.factory_class= + org.hibernate.cache.jbc2.MultiplexedJBossCacheRegionFactory]]></programlisting> + + <para> + You would end up using two JBoss Cache instances: + </para> + + <itemizedlist> + <listitem> + <para>One, for the entities, collection and queries, would use the + <literal>optimistic-entity</literal> configuration. This cache + would use optimistic locking, synchronous invalidation and would + disable initial state transfer. + </para> + </listitem> + <listitem> + <para>The second, for timestamps, would use the + <literal>timestamps-cache</literal> configuration. This cache + would use pessimistic locking, asynchronous replication and would + enable initial state transfer. + </para> + </listitem> + </itemizedlist> + + <para> + See <xref linkend="jbc-config-multiple-std"/> for more on these + standard cache configurations. + </para> + + <para> + If you hadn't set <literal>hibernate.cache.use_query_cache=true</literal> + you'd just have the single <literal>optimistic-entity</literal> cache, + shared by the entities and collections. + </para> + </sect2> + + <sect2 id="sessionfactory-multiplexed-jndi" revision="1"> + <title>The <literal>JndiMultiplexedJBossCacheRegionFactory</literal></title> + + <para> + The <literal>JndiMultiplexedJBossCacheRegionFactory</literal> + supports an additional configuration option: + </para> + + <variablelist> + <varlistentry> + <term><literal>hibernate.cache.region.jbc2.cachefactory</literal></term> + <listitem> + <para> + Specifies the JNDI name under which the + <literal>CacheManager</literal> to use is bound. + There is no default value -- the user must specify the property. + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + The <literal>JndiMultiplexedJBossCacheRegionFactory</literal> requires + that the JBoss Cache <literal>CacheManager</literal> is already + bound in JNDI; it will not create and bind one if it isn't. It is + up to the the user to ensure the cache is <literal>CacheManager</literal> + and bound in JNDI before the Hibernate <literal>SessionFactory</literal> + is created. + </para> + </sect2> + + </sect1> + + <sect1 id="jbc-config" revision="1"> + + <title>Configuring JBoss Cache</title> + + <para> + JBoss Cache provides a great many different configuration options; + here we are just going to look at a few that are most relevant + to the Second Level Cache use case. Please see the + <emphasis>JBoss Cache User Guide</emphasis> for full details. + </para> + + <sect2 id="jbc-config-single" revision="1"> + <title>Configuring a Single Standalone Cache</title> + + <para> + To configure a single standalone cache (i.e. for use by a + <literal>SharedJBossCacheRegionFactory</literal>), you need to + create a standard JBoss Cache XML configuration file and place + it on the classpath. See the <emphasis>JBoss Cache User Guide</emphasis> + and the JBoss Cache distribution for examples of JBoss Cache + configuration files. + </para> + <para> + If the resource path to your file is <literal>treecache.xml</literal>, + the <literal>SharedJBossCacheRegionFactory</literal> will find it + by default; otherwise you will need to use a configuration option + to tell it where it is. See <xref linkend="sessionfactory-shared"/> + for instruction on how to do that. + </para> + </sect2> + + <sect2 id="jbc-config-multiple" revision="1"> + <title>Managing Multiple Caches via a CacheManager</title> + + <para> + If you are using <literal>MultiplexedJBossCacheRegionFactory</literal> + you will need to provide a set of JBoss Cache configurations for + its <literal>CacheManager</literal> to use. (Or, use the set in the + <literal>jbc2-configs.xml</literal> file that ships with + <literal>hibernate-jbosscache2.jar</literal>.) The XML file used + by a <literal>CacheManager</literal> is very similar to the + usual config file used by a standalone cache; the biggest + difference is it can include multiple, named, configurations. + The format looks like this: + </para> + + <programlisting><![CDATA[<?xml version="1.0" encoding="UTF-8"?> + +<cache-configs> + + <!-- A config appropriate for entity/collection caching. --> + <cache-config name="optimistic-entity"> + + <!-- Node locking scheme --> + <attribute name="NodeLockingScheme">OPTIMISTIC</attribute> + + ..... other configuration attributes + + </cache-config> + + + <!-- A config appropriate for entity/collection caching that + uses pessimistic locking --> + <cache-config name="pessimistic-entity"> + + <!-- Node locking scheme --> + <attribute name="NodeLockingScheme">PESSIMISTIC</attribute> + + ..... other configuration attributes + + </cache-config> + +</cache-configs>]]></programlisting> + + <para> + Each <literal>&lt;cache-config&gt;</literal> element contains a complete + cache configuration, with the same contents as what you would place in + the <literal>&lt;mbean&gt;</literal> element in a standalone cache + configuration file. The <literal>name</literal> attribute on the + <literal>&lt;cache-config&gt;</literal> element provides the identifier + for the configuration; users of the <literal>CacheManager</literal> + will provide this name when requesting a JBoss Cache instance that uses + this configuration. + </para> + + </sect2> + + <sect2 id="jbc-config-detail" revision="1"> + <title>JBoss Cache Configuration Details</title> + + <para> + Let's look at how to specify a few of the JBoss Cache configuration + options that are most relevant to the Hibernate use case. + </para> + + <sect3 id="jbc-config-mode" revision="1"> + <title>CacheMode</title> + + <para> + The JBoss Cache <emphasis>CacheMode</emphasis> attribute + encapsulates whether the cache uses replication, invalidation or + local mode, as well as whether messages should be synchronous + or asynchronous. See <xref linkend="concepts-cache-attr-repl"/> + and <xref linkend="concepts-cache-attr-sync"/> for a discussion of + these concepts. + </para> + + <para> + The CacheMode is configured as follows: + </para> + + <programlisting><![CDATA[<!-- Legal modes are LOCAL + REPL_ASYNC + REPL_SYNC + INVALIDATION_ASYNC + INVALIDATION_SYNC +--> +<attribute name="CacheMode">INVALIDATION_SYNC</attribute>]]></programlisting> + + </sect3> + + <sect3 id="jbc-config-locking" revision="1"> + <title>NodeLockingScheme</title> + + <para> + The JBoss Cache <emphasis>NodeLockingScheme</emphasis> attribute + configures whether optimistic locking or pessimistic locking + should be used. See <xref linkend="concepts-cache-attr-lock"/> + for a discussion of locking. + </para> + + <para> + The NodeLockingScheme is configured as follows: + </para> + + <programlisting><![CDATA[<!-- Node locking scheme: + OPTIMISTIC + PESSIMISTIC (default) +--> +<attribute name="NodeLockingScheme">OPTIMISTIC</attribute>]]></programlisting> + + </sect3> + + <sect3 id="jbc-config-jgroups" revision="1"> + <title>JGroups <literal>Channel</literal> Configuration</title> + + <para> + Each JBoss Cache instance (except those with CacheMode + LOCAL) will need a JGroups <literal>Channel</literal>. The cache + configuration needs to tell JGroups how to set up the channel's + protocol stack. This is configured as follows: + </para> + + <programlisting><![CDATA[<attribute name="MultiplexerStack">udp</attribute>]]></programlisting> + + <para> + An alternate approach is to include the full protocol stack + configuration in the JBoss Cache configuration: + </para> + + <programlisting><![CDATA[<!-- JGroups protocol stack properties. --> +<attribute name="ClusterConfig"> + <config> + <UDP mcast_addr="228.10.10.10" + mcast_port="45588" + tos="8" + + ... many more details + + <pbcast.STATE_TRANSFER/> + <pbcast.FLUSH timeout="0"/> + </config> +</attribute>]]></programlisting> + + <para> + See <xref linkend="jgroups-config"/> for more on JGroups configuration. + </para> + </sect3> + + + <sect3 id="jbc-config-statetransfer" revision="1"> + <title>Initial State Transfer</title> + + <para> + See <xref linkend="concepts-cache-attr-state"/> for a discussion + of the concept of initial state transfer. + </para> + <para> + Initial State Transfer is configured as follows: + </para> + + <programlisting><![CDATA[<!-- Whether or not to fetch state on joining a cluster. --> +<attribute name="FetchInMemoryState">false</attribute>]]></programlisting> + + </sect3> + + <sect3 id="jbc-config-marshalling" revision="1"> + <title>Region-Based Marshalling</title> + + <para> + JBoss Cache includes a feature called <emphasis>Region Based + Marshalling</emphasis> that helps ensure the correct + classloader is in place when objects are serialized and + deserialized as part of replication and invalidation + messages. This feature adds some overhead, but it allows + your cache to work in complex classloading environments + such as those found in many application servers. It can be + disabled if your application meets the following criteria: + </para> + + <itemizedlist> + <listitem> + <para> + No cached entities use custom types (i.e. types persisted as + BLOBs or CLOBs or as a Hibernate UserType) in their + fields, and no entities use complex primary keys. + </para> + </listitem> + <listitem> + <para> + <emphasis>OR</emphasis> all custom types and complex + primary key types are visible to the classloader that + loads JGroups. + </para> + </listitem> + </itemizedlist> + + <para> + Region based marshalling is configured as follows: + </para> + + <programlisting><![CDATA[<!-- + Whether to use marshalling or not. Default is "false". +--> +<attribute name="UseRegionBasedMarshalling">true</attribute> +<!-- Must match the value of "UseRegionBasedMarshalling" --> +<attribute name="InactiveOnStartup">true</attribute>]]></programlisting> + + <para> + Region based marshalling is enabled in the standard cache + configurations that ship with + <literal>hibernate-jbosscache2.jar</literal> + </para> + </sect3> + + <sect3 id="jbc-config-eviction" revision="1"> + <title>Eviction</title> + + <para> + This topic deserves a chapter of it's own. See + <xref linkend="eviction"/>. + </para> + </sect3> + + </sect2> + + <sect2 id="jbc-config-multiple-std" revision="1"> + <title>Standard JBoss Cache Configurations</title> + + <para> + Hibernate ships with a number of standard JBoss Cache configurations + in the <literal>hibernate-jbosscache2.jar</literal>'s + <literal>jbc2-configs.xml</literal> file. The following table + highlights the key features of each configuration. + </para> + + <table frame="topbot"> + <title>Standard JBoss Cache Configurations</title> + <tgroup cols="6"> + <colspec colname="c1" colwidth="1*"/> + <colspec colname="c2" colwidth="1*"/> + <colspec colname="c3" colwidth="1*"/> + <colspec colname="c4" colwidth="2*"/> + <colspec colname="c5" colwidth="1*"/> + <colspec colname="c6" colwidth="1*"/> + <thead> + <row> + <entry>Name</entry> + <entry>Valid For</entry> + <entry>Optimal For</entry> + <entry>CacheMode</entry> + <entry>Locking</entry> + <entry>State Transfer</entry> + </row> + </thead> + <tbody> + <row> + <entry> + <property>optimistic-entity</property> + </entry> + <entry> + <property>E/C/Q</property> + </entry> + <entry> + <property>E/C/Q</property> + </entry> + <entry> + <property>INVALIDATION_SYNC</property> + </entry> + <entry> + <property>OPTIMISTIC</property> + </entry> + <entry> + <para>no</para> + </entry> + </row> + <row> + <entry> + <property>pessimistic-entity</property> + </entry> + <entry> + <property>E/C/Q</property> + </entry> + <entry> + <property>E/C/Q</property> + </entry> + <entry> + <property>INVALIDATION_SYNC</property> + </entry> + <entry> + <property>PESSIMISTIC</property> + </entry> + <entry> + <para>no</para> + </entry> + </row> + <row> + <entry> + <property>local-query</property> + </entry> + <entry> + <property>Q</property> + </entry> + <entry> + <property>Q</property> + </entry> + <entry> + <property>LOCAL</property> + </entry> + <entry> + <property>PESSIMISTIC</property> + </entry> + <entry> + <para>no</para> + </entry> + </row> + <row> + <entry> + <property>replicated-query</property> + </entry> + <entry> + <property>Q</property> + </entry> + <entry> + <property>--</property> + </entry> + <entry> + <property>LOCAL</property> + </entry> + <entry> + <property>OPTIMISTIC</property> + </entry> + <entry> + <para>no</para> + </entry> + </row> + <row> + <entry> + <property>timestamps-cache</property> + </entry> + <entry> + <property>T</property> + </entry> + <entry> + <property>T</property> + </entry> + <entry> + <property>REPL_ASYNC</property> + </entry> + <entry> + <property>PESSIMISTIC</property> + </entry> + <entry> + <para>yes</para> + </entry> + </row> + <row> + <entry> + <property>optimistic-shared</property> + </entry> + <entry> + <property>E/C/Q/T</property> + </entry> + <entry> + <property>--</property> + </entry> + <entry> + <property>REPL_SYNC</property> + </entry> + <entry> + <property>OPTIMISTIC</property> + </entry> + <entry> + <para>yes</para> + </entry> + </row> + <row> + <entry> + <property>pessimistic-shared</property> + </entry> + <entry> + <property>E/C/Q/T</property> + </entry> + <entry> + <property>--</property> + </entry> + <entry> + <property>REPL_SYNC</property> + </entry> + <entry> + <property>PESSIMISTIC</property> + </entry> + <entry> + <para>yes</para> + </entry> + </row> + </tbody> + </tgroup> + </table> + + <para> + A few notes on the above table: + </para> + + <itemizedlist> + <listitem> + <para> + <emphasis>Valid For</emphasis> and <emphasis>Optimal For</emphasis> + describe the suitability of the configuration for the four types + of data -- Entities, Collections, Queries and Timestamps. + </para> + </listitem> + <listitem> + <para><emphasis>State Transfer</emphasis> indicates whether an + initial state transfer will be performed when a cache region is + activated. + </para> + </listitem> + <listitem> + <para> + Each of the configurations uses the <literal>udp</literal> JGroups + protocol stack configuration (except <literal>local-query</literal>, + which doesn't use JGroups at all). Since they all use the same + stack, if more than one of these caches is created they will share + their JGroups resources. See <xref linkend="jgroups-config-std"/> + for a description of the standard stacks. + </para> + </listitem> + + </itemizedlist> + + <para> + These standard configurations are a good choice for many applications. + The primary reason users may want to use their own configurations is + to support more complex eviction setups. See <xref linkend="eviction"/> + for more on the kinds of things you can do with eviction. + </para> + </sect2> + + </sect1> + + <sect1 id="jgroups-config" revision="1"> + <title>JGroups Configuration</title> + + <para> + JGroups configuration is a complex area that goes well beyond the scope + of this document. Users interested in exploring the details are + encouraged to visit the JGroups website at http://www.jgroups.org as + well as the JGroups wiki page at jboss.com. + </para> + + <para> + The <literal>jgroups-stacks.xml</literal> file found in the + <literal>org.hibernate.cache.jbc2.builder</literal> package + in the <literal>hibernate-jbosscache2.jar</literal> provides a good + set of standard JGroups configurations; these should be suitable for + most needs. If you need to create your own configuration set, we + recommend that you start with this file as a base. + </para> + + <sect2 id="jgroups-config-transport" revision="1"> + <title>Transport -- UDP vs. TCP</title> + + <para> + The JGroups <emphasis>transport</emphasis> refers to the mechanism + JGroups uses for sending messages to the group members. Choosing + which transport to use is the main JGroups-related decision users + will need to make. There are three transport types: + </para> + + <itemizedlist> + <listitem> + <para> + <emphasis>UDP</emphasis> -- uses UDP multicast for transmitting + messages to all members of the group. Multicast is efficient for the + Second Level Cache use case, particularly with larger clusters, + since maintaining cache consistency means many messages need to + be sent to all members. UDP-based channel configurations are + used in the JBoss Cache configurations in the standard + <literal>jbc2-configs.xml</literal> file that ships with + Hibernate. + </para> + </listitem> + <listitem> + <para> + <emphasis>TCP</emphasis> -- uses multiple TCP unicasts + for transmitting messages to all members of the group. Less + efficient for the Second Level Cache use case, particularly as + clusters get larger, i.e. over 4 to 6 nodes. However, in some + network environments UDP multicast is not an option, in which + case TCP is available. + </para> + + <para> + If a TCP-based channel is used, there are a couple of options + available for how a channel "discovers" the other members in + the group when it first starts. + </para> + + <itemizedlist> + <listitem> + <para> + <emphasis>TCP + TCPPING</emphasis> -- here a static + list of all the possible nodes in the cluster + must be provided. The TCPPING "discovery" protocol uses + that static list to probe for available peers, using + TCP messages. The downside here is the need to provide + and maintain the static list. The upside, for multicast-averse + environments, is all communication uses TCP. + </para> + </listitem> + <listitem> + <para> + <emphasis>TCP + MPING</emphasis> -- here the MPING + "discovery" protocol uses UDP multicast to probe for + available peers; once they are detected all regular + message traffic uses TCP. The downside here, for the + multicast-averse, is that multicast is used. The upside + is there is no need for a static configuration of all + possible peers. + </para> + </listitem> + </itemizedlist> + + <para> + The TCP-based configurations in the + <literal>jgroups-stacks.xml</literal> file found in + <literal>hibernate-jbosscache2.jar</literal> all use + TCP + MPING. This is because there is no way for the + Hibernate authors to provide a meaningful static + configuration for TCPPING. If you want to use TCP + TCPPING + you will need to provide your own JGroups configuration file. + </para> + </listitem> + <listitem> + <para> + <emphasis>TUNNEL</emphasis> -- a specialized protocol designed + for cases where cluster members need to communicate across + firewalls. See the JGroups documentation for details. + </para> + </listitem> + </itemizedlist> + </sect2> + + <sect2 id="jgroups-config-std" revision="1"> + <title>Standard JGroups Configurations</title> + + <para> + By default the Second Level Cache will use JGroups configurations + found in the <literal>jgroups-stacks.xml</literal> file included in + <literal>hibernate-jbosscache2.jar</literal>. Following are their + names and a brief description of each: + </para> + + <variablelist> + <varlistentry> + <term><literal>udp</literal></term> + <listitem> + <para> + UDP multicast-based config; appropriate for all cache types. + Includes JGroups flow control (FC) which is needed for caches + that send significant numbers of asynchronous messages (i.e. + timestamp caches and entity/collection caches configured for + replication instead of invalidation). If you're not sure and + want to use UDP multicast, this is the best choice. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>udp-sync</literal></term> + <listitem> + <para> + UDP multicast-based config that omits JGroups flow control + (FC). Optimal for caches that send little or no asynchronous + messages, i.e. entity/collection caches configured for invalidation. + Unsuitable for timestamp caches or entity/collection caches + configured for replication. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>tcp</literal></term> + <listitem> + <para> + TCP-based config with UDP multicast discovery (MPING). + Includes JGroups flow control (FC); see <literal>udp</literal> + above for the significance of that. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>tcp-sync</literal></term> + <listitem> + <para> + TCP-based config with UDP multicast discovery (MPING). + Omits JGroups flow control (FC); see + <literal>udp-sync</literal> above for the significance of that. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>tunnel</literal></term> + <listitem> + <para> + Uses a specialized protocol designed for cases where cluster + members need to communicate across firewalls. See the JGroups + documentation for details. + </para> + </listitem> + </varlistentry> + </variablelist> + </sect2> + + </sect1> + +</chapter> \ No newline at end of file Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/eviction.xml =================================================================== --- core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/eviction.xml (rev 0) +++ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/eviction.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,661 @@ +<?xml version='1.0' encoding="UTF-8"?> +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> + +<!-- + ~ Copyright (c) 2008, Red Hat Middleware, LLC. All rights reserved. + ~ + ~ This copyrighted material is made available to anyone wishing to use, modify, + ~ copy, or redistribute it subject to the terms and conditions of the GNU + ~ Lesser General Public License, v. 2.1. This program is distributed in the + ~ hope that it will be useful, but WITHOUT A WARRANTY; without even the implied + ~ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + ~ Lesser General Public License for more details. You should have received a + ~ copy of the GNU Lesser General Public License, v.2.1 along with this + ~ distribution; if not, write to the Free Software Foundation, Inc., + ~ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + ~ + ~ Red Hat Author(s): Brian Stansberry + --> +<chapter id="eviction"> + + <title>Cache Eviction</title> + + <sect1 id="eviction-overview" revision="1"> + <title>Overview</title> + + <para> + <emphasis>Eviction</emphasis> refers to the process by which old, + relatively unused, or excessively voluminous data can be dropped + from the cache, allowing the cache to remain within a memory budget. + Generally, applications that use the Second Level Cache should + configure eviction, unless only a relatively small amount of + reference data is cached. This chapter provides a brief overview + of how JBoss Cache eviction works, and then explains how to configure + eviction to effectively manage the data stored in a Hibernate Second + Level Cache. A basic understanding of JBoss Cache eviction and of + concepts like FQNs is assumed; see the <emphasis>JBoss Cache User Guide</emphasis> + for more information. + </para> + + <sect2 id="eviction-overview-process" revision="1"> + <title>The Eviction Process</title> + + <para> + The JBoss Cache eviction process is fairly straightforward. Whenever + a node in a cache read or written to, added or removed, the cache + finds the <emphasis>eviction region</emphasis> (see below) that + contains the node and passes an <emphasis>eviction event</emphasis> + object to the <emphasis>eviction policy</emphasis> (see below) + associated with the region. The eviction policy uses the stream of + events it receives to track activity in the region. Periodically, + a background thread runs and contacts each region's eviction + policy. The policy uses its knowledge of the activity in the region, + along with any configuration it was provided at startup, to determine + which if any cache nodes should be evicted from memory. It then + tells the cache to evict those nodes. Evicting a node means + dropping it from the cache's in-memory state. The eviction only + occurs on that cache instance; there is no cluster-wide eviction. + </para> + + <para> + An important point to understand is that eviction proceeds + independently on each peer in the cluster, with what gets + evicted depending on the activity on that peer. There is no + "global eviction" where JBoss Cache removes a piece of data in + every peer in the cluster in order to keep memory usage inside + a budget. The Hibernate/JBC integration layer may remove some + data globally, but that isn't done for the kind of memory + management reasons we're discussing in this chapter. + </para> + + <para> + An effect of this is that even if a cache is configured for + replication, if eviction is enabled the contents of a cache will + be different between peers in the cluster; some may have evicted + some data, while others will have evicted different data. What + gets evicted is driven by what data is accessed by users on each + peer. + </para> + + <para> + Controlling when data is evicted from the cache is a matter + of setting up appropriate eviction regions and configuring + appropriate eviction policies for each region. + </para> + + </sect2> + + <sect2 id="eviction-overview-regions" revision="1"> + <title>Eviction Regions</title> + + <para> + JBoss Cache stores its data in a set of nodes organized in a tree + structure. An eviction region is a just a portion of the tree + to which an eviction policy has been assigned. The name of the + region is the FQN of the topmost node in that portion of the tree. + An eviction configuration always needs to include a special region + named <literal>_default_</literal>; this region is rooted in the + root node of the tree and includes all nodes not covered by + other regions. + </para> + <para> + It's possible to define regions that overlap. In other words, one + region can be defined for <emphasis>/a/b/c</emphasis>, and another + defined for <emphasis>/a/b/c/d</emphasis> (which is just the + <emphasis>d</emphasis> subtree of the <emphasis>/a/b/c</emphasis> + sub-tree). The algorithm that assigns eviction events to eviction + regions handles scenarios like this consistently by always choosing + the first region it encounters. So, if the algorithm needed to + decide how to handle an event affecting <emphasis>/a/b/c/d/e</emphasis>, + it would start from there and work its way up the tree until it + hits the first defined region - in this case <emphasis>/a/b/c/d</emphasis>. + </para> + </sect2> + + <sect2 id="eviction-overview-policies" revision="1"> + <title>Eviction Policies</title> + + <para> + An <emphasis>Eviction Policy</emphasis> is a class that knows how + to handle eviction events to track the activity in its region. + It may have a specialized set of configuration properties that + give it rules for when a particular node in the region should be + evicted. It can then use that configuration and its knowledge of + activity in the region to to determine what nodes to evict. + </para> + + <para> + JBoss Cache ships with a number of eviction policies. See the + <emphasis>JBoss Cache User Guide</emphasis> for a discussion of + all of them. Here we are going to focus on just two. + </para> + + <sect3 id="eviction-overview-policies-lru" revision="1"> + <title>The <literal>LRUPolicy</literal></title> + + <para> + The <literal>org.jboss.cache.eviction.LRUPolicy</literal> evicts + nodes that have been Least Recently Used. It has the following + configuration parameters: + </para> + + <itemizedlist> + <listitem> + <literal>maxNodes</literal> + - This is the maximum number of nodes allowed in this region. + 0 denotes no limit. If the region has more nodes than this, + the least recently used nodes will be evicted until the number + of nodes equals this limit. + </listitem> + + <listitem> + <literal>timeToLiveSeconds</literal> + - The amount of time a node is not written to or read (in seconds) + before the node should be evicted. 0 denotes no limit. Nodes that + exceed this limit will be evicted whether or not a + <literal>maxNodes</literal> limit has been breached. + </listitem> + + <listitem> + <literal>maxAgeSeconds</literal> + - Lifespan of a node (in seconds) regardless of idle time before + the node is swept away. 0 denotes no limit. Nodes that + exceed this limit will be evicted whether or not a + <literal>maxNodes</literal> or <literal>timeToLiveSeconds</literal> + limit has been breached. + </listitem> + + <listitem> + <literal>minTimeToLiveSeconds</literal> + - the minimum amount of time a node must be allowed to live after + being accessed before it is allowed to be considered for eviction. + 0 denotes that this feature is disabled, which is the default value. + Should be set to a value less than <literal>timeToLiveSeconds</literal>. + It is recommended that this be set to a value slightly greater + than the maximum amount of time a transaction that affects the + region should take to complete. Configuring this is particularly + important when optimistic locking is used in conjunction with + invalidation. + </listitem> + </itemizedlist> + </sect3> + + <sect3 id="eviction-overview-policies-null" revision="1"> + <title>The <literal>NullEvictionPolicy</literal></title> + + <para> + The <literal>org.jboss.cache.eviction.NullEvictionPolicy</literal> + is a simple policy that very efficiently does ... nothing. It + is used to efficiently short-circuit eviction handling for regions + where you don't want objects to be evicted (e.g. the timestamps + cache, which should <emphasis>never</emphasis> have data + evicted). Since the <literal>NullEvictionPolicy</literal> doesn't + actually evict anything, it doesn't take any configuration parameters. + </para> + </sect3> + + </sect2> + + </sect1> + + <sect1 id="eviction-organization" revision="1"> + <title>Organization of Data in the Cache</title> + + <para> + In order to understand how to configure eviction, you need to + understand how Hibernate organizes data in the cache. + </para> + + <sect2 id="eviction-organization-elements" revision="1"> + <title>Region Prefix and Region Name</title> + + <para> + All FQNs in a second level cache include two elements: + </para> + + <itemizedlist> + <listitem> + <para> + A <emphasis>Region Prefix</emphasis>, which is simply + any value assigned to the + <literal>hibernate.cache.region_prefix</literal> Hibernate + configuration property. If no Region Prefix is set, this + portion of the FQN is omitted. + </para> + <para> + If different session factories are sharing the same underlying + JBoss Cache instance(s) it is <emphasis>strongly encouraged</emphasis> + that a distinct Region Prefix be assigned to each. This will + help ensure that the different session factories cache their + data in different subtrees in JBoss Cache. + </para> + </listitem> + <listitem> + <para> + A <emphasis>Region Name</emphasis>, which is either + + <itemizedlist> + <listitem> + <para> + any value assigned to a <literal>&lt;cache&gt;</literal> element's + <literal>region</literal> attribute in a class or collection mapping. + See <xref linkend="eviction-organization-entity"/> for + an example. + </para> + </listitem> + <listitem> + <para> + Any value assigned to a Hibernate <literal>Query</literal> + object's <literal>cacheRegion</literal> property. See + <xref linkend="eviction-organization-query"/> for an + example. + </para> + </listitem> + <listitem> + <para> + The <emphasis>escaped class name</emphasis> of the type + being cached. An <emphasis>escaped class name</emphasis> + is simply a fully-qualified class name with any + <literal>.</literal> replaced with a <literal>/</literal> + -- for example <literal>org/example/Foo</literal>. + </para> + </listitem> + </itemizedlist> + </para> + </listitem> + </itemizedlist> + + </sect2> + + <sect2 id="eviction-organization-entity" revision="1"> + <title>Entities</title> + + <para> + The FQN for the cache region where entities of a particular class + is stored is derived as follows: + </para> + <para> + <literal>/</literal> + <emphasis>Region Prefix</emphasis> + <literal>/</literal> + + <emphasis>Region Name</emphasis> + <literal>/ENTITY</literal> + </para> + + <para> + If no region prefix was specified, the leading <literal>/</literal> and + <emphasis>Region Prefix</emphasis> is not included in the FQN. + So, if <literal>hibernate.cache.region_prefix</literal> was set to + "appA" and a class was mapped like this: + </para> + + <programlisting><![CDATA[<class name="org.example.Foo"> + <cache usage="transactional" region="foo_region"/> + .... +</class>]]></programlisting> + + <para> + The FQN of the region where <literal>Foo</literal> entities + would be cached is <literal>/appA/foo_region/ENTITY</literal>. + </para> + + <para> + If the class mapping does not include a <literal>region</literal> + attribute, the region name is based on the name of the entity + class, e.g. + </para> + + <programlisting><![CDATA[<class name="org.example.Bar"> + <cache usage="transactional"/> + .... +</class>]]></programlisting> + + <para> + the FQN of the region where <literal>Bar</literal> entities + would be cached is <literal>/appA/org/example/Bar/ENTITY</literal>. + </para> + </sect2> + + <sect2 id="eviction-organization-coll" revision="1"> + <title>Collections</title> + + <para> + The FQN for the cache region where entities of a particular class + is stored is derived as follows: + </para> + <para> + <literal>/</literal> + <emphasis>Region Prefix</emphasis> + <literal>/</literal> + + <emphasis>Region Name</emphasis> + <literal>/COLL</literal> + </para> + + <para> + So, let's say our example <literal>Foo</literal> entity + included a collection field <literal>bars</literal> that + we wanted to cache: + </para> + + <programlisting><![CDATA[<class name="org.example.Foo"> + <cache usage="transactional"/> + .... + <one-to-many name="bars" class="org.example.Bar"> + <cache usage="transactional" region="foo_region"/> + </one-to-many> +</class>]]></programlisting> + + <para> + The FQN of the region where the collection would be cached + would be + <literal>/appA/foo_region/COLL</literal>. + </para> + + <para> + If the collection's <literal>&lt;cache&gt;</literal> element + did not include a <literal>region</literal>, the FQN would be + <literal>/appA/org/example/Foo/COLL</literal>. + </para> + </sect2> + + <sect2 id="eviction-organization-query" revision="1"> + <title>Queries</title> + + <para> + Queries follow this pattern: + </para> + + <para> + <literal>/</literal> + <emphasis>Region Prefix</emphasis> + <literal>/</literal> + + <emphasis>Region Name</emphasis> + <literal>/QUERY</literal> + </para> + + <para> + Say we had the following query (again with a region prefix set to + "appA"): + </para> + + <programlisting><![CDATA[List blogs = sess.createQuery("from Blog blog " + + "where blog.blogger = :blogger") + .setEntity("blogger", blogger) + .setMaxResults(15) + .setCacheable(true) + .setCacheRegion("frontpages") + .list();]]></programlisting> + + <para> + The FQN of the region where this query's results would be cached + would be <literal>/appA/frontpages/QUERY</literal>. + </para> + + <para> + If the call to <literal>setCacheRegion("frontpages")</literal> + were ommitted, the <emphasis>Region Name</emphasis> portion of + the FQN would be based on a Hibernate class: + <literal>/appA/org/hibernate/cache/StandardQueryCache/QUERY</literal> + </para> + </sect2> + + <sect2 id="eviction-organization-timestamps" revision="1"> + <title>Timestamps</title> + + <para> + Timestamps follow this pattern: + </para> + + <para> + <literal>/TS/</literal> + <emphasis>Region Prefix</emphasis> + + <literal>/org/hibernate/cache/UpdateTimestampsCache</literal> + </para> + + <para> + again with a <literal>/</literal> and the <emphasis>Region Prefix</emphasis> + portion omitted if no region prefix was set. + </para> + + <para> + Note that in the timestamps case the special constant ("TS") comes + at the start of the FQN rather than the end. This makes it easier + to ensure that eviction is never enabled for the timestamps region. + </para> + </sect2> + </sect1> + + <sect1 id="eviction-organization-example" revision="1"> + <title>Example Configuration</title> + + <para> + So far we've been looking at things in the abstract; let's see an + example of how this comes together. In this example, imagine we + have a Hibernate application with the following characteristics. + + <itemizedlist> + <listitem> + <para>Query caching is enabled.</para> + </listitem> + <listitem> + <para> + There is a region prefix set as part of the Hibernate + configuration: <literal>hibernate.cache.region_prefix==appA</literal> + </para> + </listitem> + <listitem> + <para> + Some cachable entities and collections have a region + name of "reference" set in their Hibernate mapping. + </para> + </listitem> + <listitem> + <para> + Some cachable queries have the "reference" region name + set when they are created. + </para> + </listitem> + <listitem> + <para> + Other cachable entities and collections in the + <literal>org.example.hibernate</literal> package don't have a + region name set in their Hibernate mapping. + </para> + </listitem> + <listitem> + <para> + Other cachable queries don't have a region name set when they + are created. + </para> + </listitem> + </itemizedlist> + </para> + + <para> + Let's see a possible eviction configuration for this scenario: + </para> + + <programlisting><![CDATA[<attribute name="EvictionPolicyConfig"> + <config> + + <attribute name="wakeUpIntervalSeconds">5</attribute> + <attribute name="policyClass">org.jboss.cache.eviction.LRUPolicy</attribute> + + <!-- + Default region to pick up anything we miss in the more specific + regions below. + --> + <region name="/_default_"> + <attribute name="maxNodes">500</attribute> + <attribute name="timeToLiveSeconds">300</attribute> + <attribute name="minTimeToLiveSeconds">120</attribute> + </region> + + <!-- Don't ever evict modification timestamps --> + <region name="/TS" + policyClass="org.jboss.cache.eviction.NullEvictionPolicy"/> + + <!-- Reference data --> + <region name="/appA/reference"> + <!-- Keep all reference data if it's being used --> + <attribute name="maxNodes">0</attribute> + <!-- Keep it around a long time (4 hours) --> + <attribute name="timeToLiveSeconds">14400</attribute> + <attribute name="minTimeToLiveSeconds">120</attribute> + </region> + + <!-- Be more aggressive about queries on reference data --> + <region name="/appA/reference/QUERY"> + <attribute name="maxNodes">200</attribute> + <attribute name="timeToLiveSeconds">1000</attribute> + <attribute name="minTimeToLiveSeconds">120</attribute> + </region> + + <!-- + Lots of entity instances from this package, but different + users are unlikely to share them. So, we can cache + a lot, but evict unused ones pretty quickly. + --> + <region name="/appA/org/example/hibernate"> + <attribute name="maxNodes">50000</attribute> + <attribute name="timeToLiveSeconds">1200</attribute> + <attribute name="minTimeToLiveSeconds">120</attribute> + </region> + + <!-- Clean up misc queries very promptly --> + <region name="/appA/org/hibernate/cache/StandardQueryCache"> + <attribute name="maxNodes">200</attribute> + <attribute name="timeToLiveSeconds">240</attribute> + <attribute name="minTimeToLiveSeconds">120</attribute> + </region> + + </config> +</attribute>]]></programlisting> + + <para> + Notes on the above: + + <itemizedlist> + <listitem> + <para>The <literal>wakeUpIntervalSeconds</literal> configuration + controls how often the background eviction process kicks + in to evict nodes. + </para> + </listitem> + <listitem> + <para>The first <literal>policyClass</literal> configuration + sets the default eviction policy class to use for each region. + Here we want to use the standard <literal>LRUPolicy</literal> + This can be overridden on a per-region basis, as is done + here for the <literal>/TS</literal> region.</para> + </listitem> + <listitem> + <para>We set up a <literal>/_default_</literal> region. Having + such a region is a requirement if eviction is used. Here we + don't expect any data to end up in this default region, but + if by mistake someone adds a new entity type that doesn't fall + into one of our other regions, we may not have a large memory + budget for it so we evict fairly agressively. + </para> + </listitem> + <listitem> + <para>Evicting timestamps is forbidden, so we add a + <literal>/TS</literal> region that disables it. Here we + see how to override the default eviction policy.</para> + </listitem> + <listitem> + <para> + The <literal>/appA/reference</literal> region covers our + reference data entities and collections. This is our most + likely to be reused data, so we configure the cache to be + very slow to evict it. + </para> + </listitem> + <listitem> + <para> + The queries related to our reference data are less likely to + be reused, and may take up a lot of memory, so we override the + <literal>/appA/reference</literal> region with a + <literal>/appA/reference/QUERY</literal> region that is more + agressive about eviction. + </para> + </listitem> + <listitem> + <para> + The <literal>org.example.hibernate</literal> package includes a + lot of entity classes like <literal>Order</literal>, where + there are hundreds of thousands of records in the database. + These are unlikely to be reused across users, but we have a lot + of users and want to be able to cache many of them so a user + can have fast access to his or her data during the + course of their interaction with the system. So we create a + <literal>/appA/org/example/hibernate</literal> region + with a high <literal>maxNodes</literal> value but a fairly + low <literal>timeToLiveSeconds</literal>. The low time-to-live + ensures an <literal>Order</literal> is evicted quickly once a + user is done with it. + </para> + </listitem> + <listitem> + <para>Finally, cacheable queries that aren't assigned to + to the <literal>reference</literal> region will end up in + <literal>/appA/org/hibernate/cache/StandardQueryCache</literal>. + We've elected not to keep these around long at all. + </para> + </listitem> + </itemizedlist> + </para> + </sect1> + + <sect1 id="eviction-organization-best" revision="1"> + <title>Best Practices</title> + + <para> + Some best practices to follow: + </para> + + <itemizedlist> + <listitem> + <para> + Set <literal>hibernate.cache.region_prefix</literal> in your + configuration. It makes it simple to ensure the different session + factories don't step on each other if they share a JBoss Cache + instance. + </para> + </listitem> + <listitem> + <para> + Always set up an eviction region for the <literal>/TS</literal> + FQN that uses the <literal>NullEvictionPolicy</literal>. This + will ensure that timestamps never get evicted. Even if you are + not doing query caching or aren't caching timestamps in a + particular cache, this is still a good practice, as it costs + almost nothing and helps to ensure that timestamp eviction doesn't + slip in unnoticed later. + </para> + </listitem> + <listitem> + <para> + Assign a region to your entities, collections and queries rather + than relying on class names to compose the FQN. It makes + it easier to set up eviction, and helps prevent your eviction + setup breaking if class names are refactored. + </para> + </listitem> + <listitem> + <para> + Assign a different region name to your entities, collections or + queries that have different desirable eviction characteristics. + Put objects like often used reference data in one region, data + probably only accessed by a single user in another. Aggressively + evict the latter region; be less agressive with the former if + you evict it at all. + </para> + </listitem> + <listitem> + <para> + In some cases, there is an external application (i.e. outside + of Hibernate's control) that can modify data in the database. + Generally, a Second Level Cache should not be used in this sort + of case, since it can result in data in the cache being out of + date with respect to the database. But sometimes application + designers can tolerate having out of date data in the cache. In + this sort of situation, use an <literal>LRUPolicy</literal> with + a fairly low <literal>maxAgeSeconds</literal>. This will ensure + that out-of-date data eventually gets flushed from the cache. + </para> + </listitem> + </itemizedlist> + </sect1> + +</chapter> \ No newline at end of file Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/introduction.xml =================================================================== --- core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/introduction.xml (rev 0) +++ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/introduction.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,182 @@ +<?xml version='1.0' encoding="UTF-8"?> +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> + +<!-- + ~ Copyright (c) 2008, Red Hat Middleware, LLC. All rights reserved. + ~ + ~ This copyrighted material is made available to anyone wishing to use, modify, + ~ copy, or redistribute it subject to the terms and conditions of the GNU + ~ Lesser General Public License, v. 2.1. This program is distributed in the + ~ hope that it will be useful, but WITHOUT A WARRANTY; without even the implied + ~ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + ~ Lesser General Public License for more details. You should have received a + ~ copy of the GNU Lesser General Public License, v.2.1 along with this + ~ distribution; if not, write to the Free Software Foundation, Inc., + ~ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + ~ + ~ Red Hat Author(s): Brian Stansberry + --> +<chapter id="introduction"> + + <title>Introduction</title> + + <sect1 id="introduction-overview" revision="1"> + <title>Overview</title> + + <para> + JBoss Cache is a tree-structured, clustered, transactional cache. It + includes support for maintaining cache consistency across multiple + cache instances running in a cluster. It integrates with JTA transaction + managers, supporting transaction-scoped locking of cache elements and + automatic rollback of cache changes upon transaction rollback. It + supports both pessimistic and optimistic locking, with the tree-structure + of the cache allowing maximum concurrency. + </para> + + <para> + All of these features make JBoss Cache an excellent choice for use as a + Hibernate <emphasis>Second Level Cache</emphasis>, particularly in + a clustered environment. A Hibernate <literal>Session</literal> is a + transaction-scoped cache of persistent data -- data accessed via the + <literal>Session</literal> is cached in the <literal>Session</literal> + for the duration of the current transaction, and then is cleared. A + <emphasis>Second Level Cache</emphasis> is an optional cluster or + JVM-level cache whose contents are maintained beyond the life of a + transaction and whose contents can be shared across transactions. + Use of a Second Level Cache is configured as part of the configuration + of the Hibernate <literal>SessionFactory</literal>. If a Second Level + Cache is enabled, caching of an instance of a particular + entity class or of results of a particular query can be configured on + a class-by-class, collection-by-collection and query-by-query basis. + See the <emphasis>Hibernate Reference Documentation</emphasis> for more + on Second Level Cache basics and how to configure entity classes, + collections and queries for caching. + </para> + + <para> + The JBoss Cache Second Level Cache integration supports the + <literal>transactional</literal> and <literal>read only</literal> + <emphasis>cache concurrency strategies</emphasis> discussed in the + <emphasis>Hibernate Reference Documentation</emphasis>. It supports + query caching and is, of course, cluster safe. + </para> + </sect1> + + <sect1 id="introduction-requirements" revision="1"> + <title>Requirements</title> + + <para> + Second level caching with JBoss Cache 2 requires the use of JBoss + Cache 2.1.0 or later. The core JBoss Cache project is used; the + related PojoCache project/library is not needed. The following jars, + included with the JBoss Cache distribution, need to be on the classpath: + </para> + + <itemizedlist> + <listitem><para>jbosscache-core.jar</para></listitem> + <listitem><para>commons-logging.jar</para></listitem> + <listitem><para>jboss-common-core.jar</para></listitem> + <listitem><para>jgroups.jar</para></listitem> + </itemizedlist> + + <para> + JBoss Cache also needs to have the classes in the + <literal>javax.transaction</literal> package on the classpath, + but those are already included in the Hibernate distribution. + </para> + + <para> + The <literal>hibernate-jbosscache2.jar</literal> that is included with + the Hibernate distribution also needs to be on the classpath. + </para> + + <para> + A JBoss Cache configuration file, and usually a JGroups configuration + file<footnote><para><ulink url="http://labs.jboss.org/jgroups">JGroups</ulink> + is the group communication library used by JBoss Cache for intra-cluster + communication.</para></footnote>, need to be on the classpath. The + <literal>hibernate-jbosscache2.jar</literal> includes standard + configuration files in the <literal>org.hibernate.cache.jbc2.builder</literal> + package. The <literal>jbc2-configs.xml</literal> file is for JBoss + Cache and the <literal>jgroups-stacks.xml</literal> file is for JGroups. + See <xref linkend="jbc-config"/> and <xref linkend="jgroups-config"/> + for more details on these files. Users can create their own versions + and tell the <literal>SessionFactory</literal> to use them; see + <xref linkend="sessionfactory"/> for details. + </para> + + </sect1> + + <sect1 id="introduction-configuration" revision="1"> + <title>Configuration Basics</title> + + <para> + The key steps in using JBoss Cache as a second level cache are to: + </para> + + <itemizedlist> + <listitem> + <para> + Tell Hibernate in your <literal>SessionFactory</literal> + configuration that you want to use JBoss Cache 2 as your + Second Level Cache implementation: + </para> + + <programlisting><![CDATA[hibernate.cache.region.factory_class= + org.hibernate.cache.jbc2.MultiplexedJBossCacheRegionFactory]]></programlisting> + + <para> + There are a number of values that can be provided for the + <literal>hibernate.cache.region.factory_class</literal> + property, depending on how you want the JBoss Cache integration + to work. Based on what factory class you specify, there are + additional detail configuration properties you can add to further + control that factory. However, simply specifying the + <literal>MultiplexedJBossCacheRegionFactory</literal> shown + above provides a reasonable set of default values useful for + many applications. See <xref linkend="sessionfactory-factories"/> + for more details. + </para> + + <para> + Do not set the legacy <literal>hibernate.cache.provider_class</literal> + property when using JBoss Cache 2. That is a legacy property + from before Hibernate 3.3's redesign of second level caching + internals. It will not work with JBoss Cache 2. + </para> + + </listitem> + <listitem> + <para> + Tell Hibernate you want to enable caching of entities and + collections. No need to set this property if you don't: + </para> + + <programlisting><![CDATA[hibernate.cache.use_second_level_cache=true]]></programlisting> + </listitem> + <listitem> + <para> + Tell Hibernate you want to enable caching of + query results. No need to set this property if you don't: + </para> + + <programlisting><![CDATA[hibernate.cache.use_query_cache=true]]></programlisting> + </listitem> + <listitem> + <para> + If you have enabled caching of query results, tell Hibernate if + you want to suppress costly replication of those results around + the cluster. No need to set this property if you want query + results replicated: + </para> + + <programlisting><![CDATA[hibernate.cache.region.jbc2.query.localonly=true]]></programlisting> + </listitem> + </itemizedlist> + + <para> + See <xref linkend="configuration"/> for full details on configuration. + </para> + </sect1> + +</chapter> \ No newline at end of file Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/preface.xml =================================================================== --- core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/preface.xml (rev 0) +++ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/content/preface.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,166 @@ +<?xml version='1.0' encoding="UTF-8"?> +<!DOCTYPE preface PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> + +<!-- + ~ Copyright (c) 2008, Red Hat Middleware, LLC. All rights reserved. + ~ + ~ This copyrighted material is made available to anyone wishing to use, modify, + ~ copy, or redistribute it subject to the terms and conditions of the GNU + ~ Lesser General Public License, v. 2.1. This program is distributed in the + ~ hope that it will be useful, but WITHOUT A WARRANTY; without even the implied + ~ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + ~ Lesser General Public License for more details. You should have received a + ~ copy of the GNU Lesser General Public License, v.2.1 along with this + ~ distribution; if not, write to the Free Software Foundation, Inc., + ~ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + ~ + ~ Red Hat Author(s): Brian Stansberry + --> + +<preface id="preface" revision="1"> + <title>Preface</title> + + <para> + This document is focused on the use of the + <ulink url="http://labs.jboss.org/jbosscache">JBoss Cache</ulink> + clustered transactional caching library as a tool for caching data in + a Hibernate-based application. + </para> + + <para> + Working with object-oriented software and a relational database can be cumbersome + and time consuming in today's enterprise environments. Hibernate is an object/relational + mapping tool for Java environments. The term object/relational mapping (ORM) refers to + the technique of mapping a data representation from an object model to a relational + data model with a SQL-based schema. + </para> + + <para> + Hibernate not only takes care of the mapping from Java classes to + database tables (and from Java data types to SQL data types), but also provides data + query and retrieval facilities and can significantly reduce development time otherwise + spent with manual data handling in SQL and JDBC. + </para> + + <para> + In any application that works with a relational database, caching data + retrieved from the database can potentially improve application performance. + Hibernate provides a number of facilities for caching data on the + database client side, i.e. in the Java process in which Hibernate is + running. The primary facility is the Hibernate <literal>Session</literal> + itself, which maintains a transaction-scoped cache of persistent data. + If you wish to cache data beyond the scope of a transaction, it is + possible to configure a cluster or JVM-level (technically a + <literal>SessionFactory</literal>-level) cache on a class-by-class, + collection-by-collection and query-by-query basis. This type of cache + is referred to as a <emphasis>Second Level Cache</emphasis>. + </para> + + <para> + Hibernate provides a pluggable architecture for implementing its + Second Level Cache, allowing it to integrate with a number of third-party + caching libraries. This document is focused on the use of the + <ulink url="http://labs.jboss.org/jbosscache">JBoss Cache</ulink> + clustered transactional caching library as an implementation of + the Second Level Cache. It specifically focuses on JBoss Cache 2. + </para> + + <para> + If you are new to Hibernate and Object/Relational Mapping or even Java, + please follow these steps: + </para> + + <orderedlist> + <listitem> + <para> + Read the <emphasis>Hibernate Reference Documentation</emphasis>, + particularly the <emphasis>Introduction</emphasis> and + <emphasis>Architecture</emphasis> sections. + </para> + </listitem> + <listitem> + <para> + Have a look at the <literal>eg/</literal> directory in the Hibernate + distribution, it contains a simple standalone application. Copy your + JDBC driver to the <literal>lib/</literal> directory and edit + <literal>etc/hibernate.properties</literal>, specifying correct values for + your database. From a command prompt in the distribution directory, + type <literal>ant eg</literal> (using Ant), or under Windows, type + <literal>build eg</literal>. + </para> + </listitem> + <listitem> + <para> + Use the <emphasis>Hibernate Reference Documentation</emphasis> + as your primary source of information. + Consider reading <emphasis>Java Persistence with Hibernate</emphasis> + (http://www.manning.com/bauer2) if you need more help with application + design or if you prefer a step-by-step tutorial. Also visit + http://caveatemptor.hibernate.org and download the example application + for Java Persistence with Hibernate. + </para> + </listitem> + <listitem> + <para> + FAQs are answered on the Hibernate website. + </para> + </listitem> + <listitem> + <para> + Third party demos, examples, and tutorials are linked on the Hibernate + website. + </para> + </listitem> + <listitem> + <para> + The Community Area on the Hibernate website is a good resource for + design patterns and various integration solutions (Tomcat, JBoss AS, + Struts, EJB, etc.). + </para> + </listitem> + </orderedlist> + + <para> + If you are new to the Hibernate Second Level Cache or to JBoss Cache, + please follow these steps: + </para> + + <orderedlist> + <listitem> + <para> + Read the <emphasis>Hibernate Reference Documentation</emphasis>, + particularly the <emphasis>Second Level Cache</emphasis> and + <emphasis>Configuration</emphasis> sections. + </para> + </listitem> + <listitem> + <para> + Read the + <ulink url="http://labs.jboss.org/jbosscache/docs/index.html">JBoss Cache User Guide, Core Edition</ulink>. + </para> + </listitem> + <listitem> + <para> + Use this guide as your primary source of information on the + usage of JBoss Cache 2 as a Hibernate Second Level Cache. + </para> + </listitem> + </orderedlist> + + <para> + If you have questions, use the user forum linked on the Hibernate website. + The user forum on the JBoss Cache website is also useful. + We also provide a JIRA issue tracking system for bug reports and feature requests. If you + are interested in the development of Hibernate, join the developer mailing list. If + you are interested in translating this documentation into your language, contact us + on the developer mailing list. + </para> + + <para> + Commercial development support, production support, and training for Hibernate is + available through Red Hat Inc. (see http://www.hibernate.org/SupportTraining/). + Hibernate is a Professional Open Source project and a critical component of the + JBoss Enterprise Middleware System (JEMS) suite of products. + </para> + +</preface> Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/hibernate_logo_a.png =================================================================== (Binary files differ) Property changes on: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/hibernate_logo_a.png ___________________________________________________________________ Name: svn:mime-type + application/octet-stream Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/multi-cache.png =================================================================== (Binary files differ) Property changes on: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/multi-cache.png ___________________________________________________________________ Name: svn:executable + * Name: svn:mime-type + application/octet-stream Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/single-cache.png =================================================================== (Binary files differ) Property changes on: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/images/single-cache.png ___________________________________________________________________ Name: svn:executable + * Name: svn:mime-type + application/octet-stream Added: core/trunk/documentation/jbosscache2/src/main/docbook/en-US/legal_notice.xml =================================================================== --- core/trunk/documentation/jbosscache2/src/main/docbook/en-US/legal_notice.xml (rev 0) +++ core/trunk/documentation/jbosscache2/src/main/docbook/en-US/legal_notice.xml 2008-02-22 23:24:53 UTC (rev 14347) @@ -0,0 +1,52 @@ +<?xml version='1.0' encoding="UTF-8"?> +<!-- + ~ Copyright (c) 2008, Red Hat Middleware, LLC. All rights reserved. + ~ + ~ This copyrighted material is made available to anyone wishing to use, modify, + ~ copy, or redistribute it subject to the terms and conditions of the GNU + ~ Lesser General Public License, v. 2.1. This program is distributed in the + ~ hope that it will be useful, but WITHOUT A WARRANTY; without even the implied + ~ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + ~ Lesser General Public License for more details. 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