[jbosscache-issues] [JBoss JIRA] Created: (JBCACHE-1564) Using asynchronous API of JGroups for asynchronous replication

Fri Jan 15 05:17:35 EST 2010

Using asynchronous API of JGroups for asynchronous replication
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                 Key: JBCACHE-1564
                 URL: https://jira.jboss.org/jira/browse/JBCACHE-1564
             Project: JBoss Cache
          Issue Type: Patch
      Security Level: Public (Everyone can see)
          Components: Replication
    Affects Versions: 3.2.1.GA
            Reporter: Krzysztof Sobolewski
            Assignee: Manik Surtani

As I mentioned on Infinispan list, I run into some problems with NBST and asynchronous replication. Quoting my message:

***
The thing is that the "asynchronous" replication uses the usual method of 
submitting a task to an Executor. This is no problem without NBST, because the 
tasks are not interested in responses and finish immediately, but with NBSP 
they need responses to facilitate replay. And since they need to wait for 
responses, they clog the Executor's threads and under sufficiently heavy load, 
it all degrades to effectively synchronous replication. And it happens quite 
fast, really.
***

The fix in the attached patch creates a new class, AsynchronousRpcDispatcher, and makes CommandAwareRpcDispatcher extend it. The new class adds a new variant of castMessage() method - castMessageAsync(). I takes a ScheduledExecutorService where it schedules a timeout task, and a "closure" callback object, an implementation of AsyncCallback interface, which is invoked when the replication task is complete. "Completion" also means a timeout, in which case the callback is invoked with whatever responses were received.

One thing I had to do was to "hack" the GroupRequest class from JGroups to expose responsesComplete() method. I just copied it and did the necessary modification, diff of which is also attached. The method I needed is used to check whether the received responses are enough to complete the request.

There are also some minor stylistic tweaks in the patch unrelated to the real thing.

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