[infinispan-dev] Executing server tasks that contain POJOs

[Galder Zamarreño]

--
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.

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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