[
https://issues.apache.org/jira/browse/S4-4?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13126698#comment-13126698
]
Adam Wojtuniak commented on S4-4:
---------------------------------
Hi Leo,
Maybe it is possible with JBossModules, I haven't noticed that they are not
really OSGi container.
"JBoss Modules is designed to work with any existing library or application
without changes, and its simple naming and resolution strategy is what makes
that possible. Unlike OSGi, JBoss Modules does not implement a container;
rather, it is a thin bootstrap wrapper for executing an application in a
modular environment. The moment your application takes control, the modular
environment is ready to load and link modules as needed. Furthermore, modules
are never loaded (not even for resolution purposes) until required by a
dependency, meaning that the performance of a modular application depends only
on the number of modules actually used (and when they are used), rather than
the total number of modules in the system. And, they may be unloaded by the
user at any time."
I am going to investigate that what I can do with that solution.
Regards,
Adam
On Thu, Oct 13, 2011 at 4:44 PM, Leo Neumeyer wrote:
When I tried jboss modules, I didn't have to do any of this. Maybe it
is worth investing more times in getting jboss modules to work.
I started a jira for this topic here:
https://issues.apache.org/jira/browse/S4-4
please add to this issue.
-leo
> Dynamic App Loading
> -------------------
>
> Key: S4-4
> URL: https://issues.apache.org/jira/browse/S4-4
> Project: Apache S4
> Issue Type: New Feature
> Reporter: Leo Neumeyer
>
> We want to be able to load and unload applications dynamically. Here is some
> background information:
> Once a server is started, we expect it to run indefinitely until there is a
> failure or we need to upgrade the framework software or we change the cluster
> configuration. In S4, the cluster is symmetric, that is, all the nodes are
> identical, with the same code base and the same configuration.
> Applications are loaded dynamically after the cluster is started. If app1
> depends on app2, then app2 needs to use an EventSource to publish events.
> Apps must be able to find EventSource and subscribe to it during
> initialization.
> When an app is unloaded, it will close its EventSource(s). This in turn, will
> close all the streams that are subscribed. The apps that own the streams are
> responsible for taking action once their dependencies are gone.
> Possible roadmap:
> M1:
> - Server starts with no apps.
> - Apps are loaded during initialization, for example by searching an
> app directory.
> - Apps are initialized (no dependencies among apps).
> - Apps are started.
> M2:
> - Add dependencies among apps using EventSource.
> M3:
> - Add runtime loading/unloading functionality
> Leo implemented a solution using JBOSS Modules which seems simpler than using
> OSGI. Modules seems to work but is not well documented which makes it hard to
> use without understanding the low level details. See the commented out code
> here:
> https://github.com/leoneu/s4-piper/blob/master/subprojects/s4-core/src/main/java/io/s4/core/Server.java
> From Adam:
> Yes I have a few ideas but I need couple days to implement them.
> First, is to build S4 and examples as proper OSGi bundles using gradle osgi
> plugin http://gradle.org/osgi_plugin.
> Its using bnd tool http://www.aqute.biz/Bnd/Bnd.
> Then embed osgi container (using standard osgi api) in Controller instead of
> JBoss modules see
> http://felix.apache.org/site/apache-felix-framework-launching-and-embedding.html.
> and configure directory from which felix should auto deploy our examples
> http://felix.apache.org/site/apache-felix-framework-usage-documentation.html#ApacheFelixFrameworkUsageDocumentation-autodeploy.
> For dynamic deployment we can use file install bundle
> http://felix.apache.org/site/apache-felix-file-install.html, it will watch
> directory from which it loads new bundles.
> To configure properly examples we can use ipojo
> http://felix.apache.org/site/apache-felix-ipojo.html or declarative services
> http://felix.apache.org/site/apache-felix-service-component-runtime.html,
> they both using service component model and are not intrusive in the code.
> That will be enough to load properly the apps.
> Later we have to think how we want to use osgi in s4, just to load apps or
> properly use service management. Bundles are hiding the internals from other
> bundles and should communicate through well defined services. And also I
> don't have clear picture how s4 is going to be distributed (have to look more
> at https://github.com/s4/s4). Maybe you can write me some small description
> of s4 concept.
> ...
> I've implemented ideas which I sent you before. Now I can load the apps using
> embedded osgi container but there is still class loading issue
> (com.esotericsoftware.kryo.SerializationException: Unable to find class:
> io.s4.example.counter.UserEvent). To be able to run s4 I had to put plenty
> system packages in configuration file for felix.
> Around 15 jars defined in libraries are not osgi bundles (don't have proper
> manifest file). The biggest issue are dependencies and classloading (for
> example Kryo is trying to load UserEvent class but that class is not visible
> for him so Class.forName is not going to work).I will try to fix these
> problems, in the meantime you can have a look at my repo
> https://github.com/adamwojtuniak/s4-piper. I added task createRepo, it will
> create bundles directory with all dependencies and project jars. When you
> launch Main class from s4-core, it launches embedded felix which will auto
> deploy all bundles located in bundles directory. In the console you will see
> felix gogo shell ( http://www.packtpub.com/article/apache-felix-gogo ).
> From Henry:
> Ugh, I was actually trying to avoid OSGI if I can =)
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
