[infinispan-dev] Executing server tasks that contain POJOs

Dan Berindei dan.berindei at gmail.com
Thu Mar 30 12:33:59 EDT 2017


On Thu, Mar 30, 2017 at 3:51 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.
>

I know Sanne also wanted to add one of the query modules as an
optional dependency to the core module for a similar reason, but it
seems really hacky.

Could the server create the GlobalConfigurationBuilder with a
classloader that has access to the query module instead?

Alternatively, I know ModularClassResolver prefixes class names with
the slot and module name, and can load a class from any module. Maybe
we could also allow a slot:module:class format everywhere the
configuration currently accepts a class name?

> 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
> --
> Galder Zamarreño
> Infinispan, Red Hat
>
>
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