[
https://issues.apache.org/jira/browse/S4-4?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13137163#comment-13137163
]
Matthieu Morel commented on S4-4:
---------------------------------
I fixed the issue you mentioned in apploading test and pushed it to your master
branch (includes your own changes).
This was due to gradle and eclipse using different output directories for
compiled classes. This is actually deliberately configured by gradle, and it
seems a good idea to leave it like that. The issue only affected the apploading
test, and is fixed by resolving the output directory for test files at runtime,
taking into account the execution environment (see my comments in
TestUtils#findDirForCompiledTestClasses() )
> 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
> Assignee: Matthieu Morel
> Fix For: 0.5
>
>
> 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
