[infinispan-dev] Executing server tasks that contain POJOs

[Galder Zamarreño]

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].

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
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Galder Zamarreño
Infinispan, Red Hat