[jboss-cvs] JBossAS SVN: r82585 - projects/docs/community/5/Clustering_Guide/en-US.
jboss-cvs-commits at lists.jboss.org
jboss-cvs-commits at lists.jboss.org
Fri Jan 2 00:10:14 EST 2009
Author: bstansberry at jboss.com
Date: 2009-01-02 00:10:14 -0500 (Fri, 02 Jan 2009)
New Revision: 82585
Modified:
projects/docs/community/5/Clustering_Guide/en-US/Clustering_Guide_HTTP.xml
Log:
[JBAS-6359] Get a better nested hierarchy
Modified: projects/docs/community/5/Clustering_Guide/en-US/Clustering_Guide_HTTP.xml
===================================================================
--- projects/docs/community/5/Clustering_Guide/en-US/Clustering_Guide_HTTP.xml 2009-01-02 04:41:10 UTC (rev 82584)
+++ projects/docs/community/5/Clustering_Guide/en-US/Clustering_Guide_HTTP.xml 2009-01-02 05:10:14 UTC (rev 82585)
@@ -3,9 +3,10 @@
<chapter id="clustering-http">
<title>HTTP Services</title>
- <para>HTTP session replication is used to replicate the state associated with your web clients on other
- nodes of a cluster. Thus, in the event one of your node crashes, another node in the cluster will be
- able to recover. Two distinct functions must be performed:</para>
+ <para>HTTP session replication is used to replicate the state associated
+ with web client sessions to other nodes in a cluster. Thus, in the event
+ one of your nodes crashes, another node in the cluster will be
+ able to recover. Two distinct functions must be performed:</para>
<itemizedlist>
<listitem>
<para>Session state replication</para>
@@ -14,21 +15,44 @@
<para>Load-balancing of incoming invocations</para>
</listitem>
</itemizedlist>
- <para>State replication is directly handled by JBoss. When you run JBoss in the <literal>all</literal>
- configuration, session state replication is enabled by default. Just configure your web application as distributable in its <filename>web.xml</filename> (see below), deploy it, and its session state is automtically replicated across all JBoss instances in the cluster.</para>
- <para>However, load-balancing is a different story; it is not handled by JBoss itself and requires an external load balancer. aThis function could be provided by specialized hardware switches or routers (Cisco LoadDirector for example) or by specialized software running on commodity hardware. As a very common scenario, we will demonstrate how to set up a software load balancer using Apache httpd and mod_jk.</para>
+ <para>State replication is directly handled by JBoss. When you run JBoss
+ in the <literal>all</literal> configuration, session state replication is
+ enabled by default. Just configure your web application as
+ <literal><distributable></literal> in its <filename>web.xml</filename> (see below),
+ deploy it, and its session state is automtically replicated across all
+ JBoss instances in the cluster.</para>
+ <para>However, load-balancing is a different story; it is not handled by
+ JBoss itself and requires an external load balancer. This function could
+ be provided by specialized hardware switches or routers (Cisco LoadDirector
+ for example) or by specialized software running on commodity hardware.
+ As a very common scenario, we will demonstrate how to set up a software
+ load balancer using Apache httpd and mod_jk.</para>
<note><title>Note</title>
- <para>A load-balancer tracks HTTP requests and, depending on the session to which the request is linked, it dispatches the request to the appropriate node. This is called load-balancing with sticky-sessions: once a session is created on a node, every future request will also be processed by that same node. Using a load-balancer that supports sticky-sessions but not configuring your web application for session replication allows you to scale very well by avoiding the cost of session state replication: each query will always be handled by the same node. But in case a node dies, the state of all client sessions hosted by this node (the shopping carts, for example) will be lost and the clients will most probably need to login on another node and restart with a new session. In many situations, it is acceptable not to replicate HTTP sessions because all critical state is stored in a database. In other situations, losing a client session is not acceptable and, in this case!
, session state replication is the price one has to pay.</para>
+ <para>A load-balancer tracks HTTP requests and, depending on the session
+ to which the request is linked, it dispatches the request to the
+ appropriate node. This is called load-balancing with sticky-sessions
+ or session affinity: once a session is created on a node, every future
+ request will also be processed by that same node. Using a load-balancer
+ that supports sticky-sessions but not configuring your web application
+ for session replication allows you to scale very well by avoiding the
+ cost of session state replication: each request for a session will
+ always be handled by the same node. But in case a node dies, the state
+ of all client sessions hosted by this node (the shopping carts, for
+ example) will be lost and the clients will most probably need to login
+ on another node and restart with a new session. In many situations, it
+ is acceptable not to replicate HTTP sessions because all critical state
+ is stored in a database. In other situations, losing a client session
+ is not acceptable and, in this case, session state replication is the
+ price one has to pay.</para>
</note>
<section><title>Configuring load balancing using Apache and mod_jk</title>
<para>Apache is a well-known web server which can be extended by plugging in modules. One of these modules, mod_jk has been specifically designed to allow the forwarding of requests from Apache to a Servlet container. Furthermore, it is also able to load-balance HTTP calls to a set of Servlet containers while maintaining sticky sessions, which is what is most interesting for us in this section.</para>
-</section>
<section id="clustering-http-download">
<title>Download the software</title>
<para>First of all, make sure that you have Apache installed. You can download Apache directly from
@@ -239,7 +263,7 @@
</note>
</section>
-
+ </section>
<section id="clustering-http-state">
<title>Configuring HTTP session state replication</title>
<para>The preceding discussion has been focused on using mod_jk as a load balancer. The content of the remainder our discussion of clustering HTTP services in JBoss AS applies no matter what load balancer is used.
@@ -327,7 +351,6 @@
</listitem>
</itemizedlist>
- </section>
<section id="clustering-http-app">
@@ -518,6 +541,7 @@
attributes. JBoss cache automatically figures out how to handle those collections and replicate
field changes in their member objects.</para>
</section>
+ </section>
<section id="clustering-http-monitor">
<title>Monitoring session replication</title>
<para> If you have deployed and accessed your application, go to the
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