[infinispan-dev] Executing server tasks that contain POJOs

[Gustavo Fernandes]

On Thu, Mar 30, 2017 at 4:49 PM, Galder Zamarreño <galder at redhat.com> wrote:

>
> --
> Galder Zamarreño
> Infinispan, Red Hat
>
> > On 30 Mar 2017, at 17:15, Gustavo Fernandes <gustavo at infinispan.org>
> wrote:
> >
> >
> >
> > On Thu, Mar 30, 2017 at 1:51 PM, Galder Zamarreño <galder at redhat.com>
> wrote:
> > Hi all,
> >
> > For a demo I'm giving next week, I'd like to show how to use distributed
> streams via a remote server task. All server tasks that we have in
> testsuite rely on primitives but in my case I wanted to use POJOs.
> >
> > To do that, I needed to get compatibility mode working in such way that
> those POJOs could be unmarshalled for the server task. Since in another
> demo I'm showing Protostream based POJOs, I thought I'd try to use that as
> mechanism to unmarshall POJOs server side.
> >
> > We have a test for such scenario [1], but the reality (running on a
> proper server) is anything that simple. Here's a list of things I've found
> out while creating a WordCount example that relies on a POJO:
> >
> > 1. Out of the box, it's impossible to set compatibility marshaller to
> org.infinispan.query.remote.CompatibilityProtoStreamMarshaller [1]
> because "org.infinispan.main" classloader can't access that class. I worked
> around that by tweaking the module.xml to have an optional dependency to
> "org.infinispan.remote-query.server" module.
> >
> > 2. After doing that, I had to register the protofile and associated
> classes remotely in the server. Again, there's no out of the box mechanism
> for that, so I created a remote server task that would do that [3].
> >
> >
> > AFAICT, you should be able to do that doing a PUT in the
> Protobuf_Metadata cache, which entails having auth enabled. This cache
> should be REPL_SYNC, so no need to run a server task.
>
> Good point but not so sure it completely removes the need for the task.
> The task does two things:
>
> 1. Call ProtobufMetadataManager.registerProtofile, which as you say could
> be swapped with a cache.put on the metadata cache.
>
> 2. Call ProtobufMetadataManager.registerMarshaller. This goes deep into
> updating SerializationContextImpl, which seems independent of any
> replicated cache.
>


AFAICT (again), there is an internal listener or interceptor that upon
metadata cache change, will update the SerCtx on all nodes.

Gustavo


>
> In fact, I had originally set up the task to execute in only in one node,
> but when I did that I found that marshallers were not registered in all
> nodes, so I had to execute the task in all nodes.
>
> I guess the task could be just limited to only executing 2.) in all nodes
> (and store the protofile contents by accessing the cache remotely), but I
> can't see how I can avoid the task altogether right now.
>
> >
> >
> >
> > 3. Finally, with all that in place, I was able to complete the WordCount
> test [4] with a final caveat: the return of the word count, and words
> protofile registration, tasks return objects that are not marshalled by the
> compatibility marshaller, so I had to make sure that the remote cache
> manager used for those tasks uses the default marshaller.
> >
> > Clearly we need to improve on this, and we have plans to address these
> issues (with new upcoming transcoding capabilities), but I thought it'd be
> worth mentioning the problems found in case anyone else encounters them
> before transcoding is in place.
> >
> > Cheers,
> >
> > [1] https://github.com/galderz/datagrid-patterns/blob/master/
> server-config/domain/domain.xml#L139
> > [2] https://github.com/galderz/datagrid-patterns/blob/master/
> server-config/org.infinispan.main_module.xml#L18
> > [3] https://github.com/galderz/datagrid-patterns/blob/master/
> analytics-stream/tasks-server/src/main/java/test/WordsProtoTask.java
> > [4] https://github.com/galderz/datagrid-patterns/blob/master/
> analytics-stream/tasks-client/src/test/java/test/WordCountTest.java
> > --
> > Galder Zamarreño
> > Infinispan, Red Hat
> >
> >
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