<html><head><meta http-equiv="Content-Type" content="text/html charset=iso-8859-1"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On 17/08/2012, at 1:42 AM, Thomas Diesler <<a href="mailto:thomas.diesler@jboss.com">thomas.diesler@jboss.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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<tt>Regarding ...<br>
</tt>
<blockquote><tt><i>This sounds very non-deterministic. Just to
clarify, are you saying that if the user has a complex bundle
deployment with lots of inter-dependencies on startup some may
be resolved and some won't, and this may change on subsequent
startups depending on the order in which they start?</i><br>
</tt></blockquote>
<tt>With a complex set of bundle deployments the user will have to
deploy them in a known order (which is a problem in itself). There
is pull request <a href="https://github.com/jbossas/jboss-as/pull/2790">#2790</a>
waiting that will allow the management client to have control over
the auto start behaviour. So a user could first install the
complete set in multiple operations and later explicitly start a
selected set of bundles. This would overcome the order issue on
first deploy.<br></tt></div></blockquote><div><br></div><div>I really don't like this solution. I think that the best solution here is passive deployments, that don't start POST_MODULE until all their dependencies are available. In this case it does not have to be a explicit dependency on potential future bundles, but you you could have a 'resolved' service that acts as a gate, once OSGI has resolved the bundle it creates this service, which will then trigger the deployment to continue.</div><br><blockquote type="cite"><div text="#000000" bgcolor="#FFFFFF"><tt>
<br>
Once the bundles are installed and activated the framework records
their respective state. On server restart these persistent bundles
are deployed in an arbitrary order but there is a guarantee backed
into the Framework integration layer that ensures that the first
resolve attempt is made after all persistent bundles have been
installed. From the resolve perspective order also matters - you
might get different wiring results depending on the order you
resolve the bundles. One possible approach might be to resolve the
full set of persistent bundles at once, but the guarantee for an
identical wiring is still weak. A better approach would be to
always resolve in a known order (i.e. sort by bundle id). The
still better solution would be to persist the last known wiring
graph and restore that on startup. Currently, the persistent
bundles are resolved in the order they hit the
BundleResolveProcessor which is arbitrary AFAIK.<br></tt></div></blockquote><div><br></div><div>I think that this needs to be deterministic, otherwise we will end up with a situation where deploying the same thing to a domain results in different wirings for each server in the domain. Persisting the wiring does not really help in this case. IMHO any form of non-determinism is a serious bug.</div><div><br></div><div>Stuart</div><br><blockquote type="cite"><div text="#000000" bgcolor="#FFFFFF"><tt>
<br>
I have written up the complete subsystem activation process in <a href="https://community.jboss.org/wiki/OSGiSubsystemActivationProcess">this
article</a>. It contains the known issues and ideas for possible
solutions. Perhaps we can start from there to find a more
consistent solution.<br>
<br></tt></div></blockquote><div><br></div><div><br></div><br><blockquote type="cite"><div text="#000000" bgcolor="#FFFFFF"><tt>
cheers<br>
--thomas <br>
</tt><br>
<div class="moz-cite-prefix">On 08/15/2012 01:32 PM, Thomas Diesler
wrote:<br>
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<div class="moz-cite-prefix">On 08/15/2012 11:20 AM, Stuart
Douglas wrote:<br>
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<div>On 15/08/2012, at 6:59 PM, Thomas Diesler <<a moz-do-not-send="true" href="mailto:thomas.diesler@jboss.com">thomas.diesler@jboss.com</a>>
wrote:</div>
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<div text="#000000" bgcolor="#FFFFFF"> <tt>> Why would
the OSGI bundle not be able to resolve, is it because is
waiting for another OSGI bundle to be installed?<br>
<br>
This is by virtue of the API - BundleContext.install()
does not resolve the bundle. As the method name
suggests, it just installs the bundle. <br>
<br>
In the hot-deployment case it is debatable whether
bundle resolution and later bundle activation should be
attempted or not. By design, the order of bundle
deployment is not the responsibility of the user but
that of the framework. For a complex graph of
interdependent bundles the user cannot possibly be asked
to deploy them in the "right order". Instead the API
allows to INSTALL the complete set (i.e. make the
metadata available to the resolver) and later activate
the bundles as needed. There are other triggers for
bundle resolution too (e.g. resource access)<br>
<br>
We currently do resolve/activate during DUP processing
on a trial basis. For a bundle that only has
dedependencies on already installed bundles the
resolve/activation works fine and the services become
available. I guess this is the expected hot-deploy
behaviour. A bundle that cannot resolve - for various
reasons, one being the user says so - we dont attempt to
start the bundle either. It would still run through all
remaining DUPs but does not have a module attached.<br>
</tt></div>
</blockquote>
<div><br>
</div>
<div>This sounds very non-deterministic. Just to clarify, are
you saying that if the user has a complex bundle deployment
with lots of inter-dependencies on startup some may be
resolved and some won't, and this may change on subsequent
startups depending on the order in which they start?</div>
</div>
</blockquote>
<tt>Yes, this is a long outstanding issue [<a moz-do-not-send="true" href="https://issues.jboss.org/browse/AS7-378">AS7-378</a>]. I
still have no guarantee that all bundles in a given set have
been INSTALLED (in OSGi terminology) / have completed the
Phase.REGISTER phase (in AS7 terminology) when the one bundle
hits the BundleResolveProcessor. The framework records the
persistent bundle state and on restart it is a requirement that
all persistent bundles reach their respective target state for
successful framework initialization. There is a little more
detail to it and I'd be more than happy to work with you to find
a consistent solution. We can take up this topic in another osgi
specific thread if you like.<br>
</tt>
<blockquote cite="mid:7FAB89A5-233F-49DA-9177-44461AE7F8DA@gmail.com" type="cite">
<div><br>
<blockquote type="cite">
<div text="#000000" bgcolor="#FFFFFF"><tt> <br>
Non-OSGi deployments that use jboss-modules metadata to
define their dependencies (i.e. Dependencies clause in
the manifest) have that problem too, but worse. A
complex system of interdependent module deployments is
likely not manageable because of this ordering issue.
Even if the user gets the ordering right the first time,
on server restart the notion of deployment order is lost
and very likely initial deployments will fail with no
osgi involved. Granted that this describes a use case
that is not intended to be used for user deployments. <br>
</tt></div>
</blockquote>
<div><br>
</div>
<div>No, JBoss modules uses MSC services to resolve the
dependencies. At container start all deployments are now run
as part of the boot ops, so as long as all deployments are
present this will always work. We do need a more specified
way of saying "Don't start this deployment until another
deployment is done", but this is mainly for things like
EJB's, not for class loading. <br>
</div>
</div>
</blockquote>
<tt>Considering use case: moduleA depends on moduleB. On restart
both deployments are processed in parallel. Even with 100 other
deployments in between it is guaranteed that moduleA wont run
into "missing service on next phase" error because the module
service for B has not been installed? If so I take back the
above prediction on restart, but still hold the unmanageable
claim because ordering is delegated to the user (i.e. he must
get it right the first time).<br>
<br>
</tt>
<blockquote cite="mid:7FAB89A5-233F-49DA-9177-44461AE7F8DA@gmail.com" type="cite">
<div><br>
<blockquote type="cite">
<div text="#000000" bgcolor="#FFFFFF"><tt> <br>
> the classic one is deployment of JDBC drivers that
have an OSGI manifest<br>
<br>
We already removed the hack that disables OSGi for this
case. The JDBC driver *is* an OSGi bundle because it
contains valid OSGi metadata. It gets processed as such
and should work as expected. All DUP processing is
identical as before except the way module dependencies
are computed and how the Module service is created. The
only case where an OSGi bundle gets treated as a library
jar is when it is located in an EAR/lib directory.
Bundles contained in EARs are otherwise processed as
OSGi sub deployments.</tt><br>
</div>
</blockquote>
<div><br>
</div>
<div>It sounds like because we have removed the hack JDBC
drivers now will not work if they fail to resolve?</div>
</div>
</blockquote>
<tt><br>
If they fail to resolve it would be because a requirement
specified by the JDBC driver cannot be satisfied (e.g. wrong
execution environment, missing package wire). I'd say the
deployment of that driver should fail at resolve time because it
would not work anyway because of the missing wire to a valid
capability. Please don't forget that the requirements given by
author should be honoured and satisfied if you want the driver
to work - they should not be ignored or replaced by some made up
hard wires that happen to work. In this respect a JDBC driver is
no different to any other OSGi bundle.<br>
<br>
</tt>
<blockquote cite="mid:7FAB89A5-233F-49DA-9177-44461AE7F8DA@gmail.com" type="cite">
<div><br>
<blockquote type="cite">
<div text="#000000" bgcolor="#FFFFFF"> <br>
<tt>> we should not be allowing the presence of the
OSGI subsystem to provide a different experience for
users that are only after EE functionality <br>
<br>
Agreed, EE deployments should not be effected - and I
don't think they are. The OSGi subsystem is not
activated unless #1 you do so by management op #2 you
deploy a bundle #3 some component is an injection target
for the system BundleContext<br>
<br>
> We remove OSGI from the default profile, and
provide a standalone-osgi.xml for users that wish to use
OSGI<br>
<br>
AFAICS this would remove a few services that are already
lazy and a few DUPs that deal with bundle deployments. W</tt><tt>e
already have t</tt><tt>he configuration for a pure OSGi
runtime as you suggest. Removing the OSGi subsystem from
the default profile would not solve the need for DUP
authors to be aware of OSGi deployments and code for the
case of unresolved bundle deployments.<br>
</tt></div>
</blockquote>
<div><br>
</div>
<div>Even if we resolve the module issue I still think that it
would be worth making this a separate profile. Like Jaikiran
I really don't like the idea of other subsystems having to
code around OSGI. Another possibility we could potentially
explore is a separate deployment chain for OSGI, so these
DUP's do not even run if it is an OSGI deployment. <br>
</div>
</div>
</blockquote>
<tt>The purpose of OSGi integration in AS7 is to make middleware
services that come with AS7 available to modular applications
that use the OSGi standard and vice versa (i.e. make OSGi
services available to EE components). We are not trying to build
a standalone OSGi runtime and compete with <a moz-do-not-send="true" href="http://www.eclipse.org/virgo/">Virgo</a>,
<a moz-do-not-send="true" href="http://karaf.apache.org/">Karaf</a>,
etc. Instead, we are competing against WebSphere, WebLogic,
Glassfish - which AFAIK all use OSGi as their bottom most layer
and increasingly so make this tech available to user
deployments. From the business perspective the ability to
architect non-trivial modular applications in a standard way is
a requirement on the product sheet. <br>
</tt>
<blockquote cite="mid:7FAB89A5-233F-49DA-9177-44461AE7F8DA@gmail.com" type="cite">
<div>
<div><br>
</div>
<div>Do we have any usage data on how many of our users
actually use OSGI? The more I think about it the more I
think it makes sense to leave it out of the default profile.
Even though you say 'it is not active unless you deploy a
bundle', the thing is that many JDBC driver have OSGI
metadata, so users that simply want to setup a datasource
will still have OSGI activating, which is usually not what
they would want.</div>
</div>
</blockquote>
<tt>I have download stats on sourceforge for the jbosgi umbrella
which are <a moz-do-not-send="true" href="http://sourceforge.net/projects/jboss/files/JBossOSGi/stats/timeline?dates=2012-01-01+to+2012-08-15">around
3000/month</a>. I also know of a few large EAP accounts that
are using this tech or have it as a decision maker for EAP
yes/no. The reason that many JDBC drivers have OSGi metadata is
because they *are* OSGi bundles and want their requirements to
be honoured in a given runtime. OSGi subsystem startup should be
quick and flawless and those driver bundles should work seamless
in AS7. They currently do AFAIK - if not I'd be interested in
the details. <br>
</tt>
<blockquote cite="mid:7FAB89A5-233F-49DA-9177-44461AE7F8DA@gmail.com" type="cite">
<div>
<div><br>
</div>
<div>Stuart</div>
<br>
<blockquote type="cite">
<div text="#000000" bgcolor="#FFFFFF"><tt><br>
</tt><tt>> OSGI deployment that cannot be resolved
pause the deployment process until such time as they can
be <br>
<br>
Yes, this is very much in line with what I think how it
should work. The management API should allow the user to
specify whether a deployment should get
resolved/activated too. As a desired side effect this
could introduce life cycle for any AS7 deployment (i.e.
start/stop decoupled from deploy/undeploy). I already
did some work in this direction related to in "<a moz-do-not-send="true" href="https://issues.jboss.org/browse/AS7-2777">Add
notion of start/stop for deployments</a>". It builds
on top of "<a moz-do-not-send="true" href="https://issues.jboss.org/browse/AS7-3694">Allow
management client to associate metadata with
DeploymentUnit</a>", which is waiting to get <a moz-do-not-send="true" href="https://github.com/jbossas/jboss-as/pull/2790">pulled</a>.<br>
<br>
> which means that there will always be a Module
available <br>
<br>
YES ;-)<br>
<br>
cheers<br>
--thomas<br>
</tt><br>
<div class="moz-cite-prefix">On 08/15/2012 07:26 AM,
Stuart Douglas wrote:<br>
</div>
<blockquote cite="mid:2ABFD913-B778-4469-83B8-607BE9BDC902@gmail.com" type="cite">
<pre wrap="">Why would the OSGI bundle not be able to resolve, is it because is waiting for another OSGI bundle to be installed? And if so, wouldn't it make more sense to pause the deployment process until the bundle can be resolved? Otherwise the behaviour will be different depending on when the bundle is resolved (e.g. if a bundle is resolved late it will not have EJB's deployed, if it is resolved early it will).
I really hate the way that OSGI takes over and prevents the module being created, I am pretty sure that the number of users that this has caused problems for is larger than the number of users that actually use OSGI (the classic one is deployment of JDBC drivers that have an OSGI manifest).
I think we really need a solution for this for AS 7.2, because as it currently stands we are primarily an EE app server, and we should not be allowing the presence of the OSGI subsystem to provide a different experience for users that are only after EE functionality.
To this end, I propose the following:
- We remove OSGI from the default profile, and provide a standalone-osgi.xml for users that wish to use OSGI, this way OSGI cannot affect users that simply want EE functionality
- OSGI deployment that cannot be resolved pause the deployment process until such time as they can be, by making the POST_MODULE DeploymentUnitPhaseService passive, which means that there will always be a Module available.
What do you think?
Stuart
On 15/08/2012, at 3:05 PM, Thomas Diesler <a moz-do-not-send="true" class="moz-txt-link-rfc2396E" href="mailto:thomas.diesler@jboss.com"><thomas.diesler@jboss.com></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Folks,
a quick reminder that you cannot assume a valid Module attachment in
Phase.POST_MODULE or after.
An OSGi deployment that cannot resolve won't have a Module attached to
the DU. There is talk about aligning the deployment phase names with
Bundle life cycle terminology. IMHO Phase.POST_MODULE and Phase.INSTALL
are not so lucky names because they imply meaning that may not be true.
For suggested improvement see <a moz-do-not-send="true" class="moz-txt-link-freetext" href="https://issues.jboss.org/browse/AS7-3585">https://issues.jboss.org/browse/AS7-3585</a>
This is related to: <a moz-do-not-send="true" class="moz-txt-link-freetext" href="https://issues.jboss.org/browse/AS7-5376">https://issues.jboss.org/browse/AS7-5376</a>
cheers
--thomas
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