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Date: Thu, 23 Feb 2012 12:10:09 +1100
From: Aristedes Maniatis <ari@maniatis.org>
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To: dev@cayenne.apache.org
Subject: Re: Non-blocking DataRowStore - need help to test
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On 23/02/12 5:54 AM, Andrus Adamchik wrote:
> Here is a potentially disruptive change to Cayenne core:
>
> http://svn.apache.org/viewvc?view=revision&revision=1292437
> (also see https://issues.apache.org/jira/browse/CAY-1670 )
>
> This removes the major global lock and has a potential to significantly increase throughput (which is an issue, see CAY-1124 by Tore for instance). The implementation is based on a previously untried by us data structure - ConcurrentLinkedHashMap - http://code.google.com/p/concurrentlinkedhashmap/ . It is used by Apache Cassandra, so presumably it works and can handle the load. I internalized this code, placing it under org.apache.cayenne.util.concurrentlinkedhashmap.
>
> I need help with testing though... Maybe someone has any kind of load tests that can emulate multiple DataContexts attached to a single ServerRuntime and performing various select/modify operations? Or maybe you are daring enough to place this in production? I will do the same on my end.
>
> To give some reassurance, our single-threaded unit tests pass 100% with no changes after I swapped commons-collections LRUMap to ConcurrentLinkedHashMap.
>
> Appreciate feedback on this feature!


Some questions rather than feedback at this stage:

* ConcurrentLinkedHashMap seems to have a roadmap http://code.google.com/p/concurrentlinkedhashmap/wiki/Changelog and ongoing development. Since this is the case, is it wise to fork it into the Cayenne source rather than link to the built artifacts and make it easier to update in the future?

* How does this new code interact and relate to third party caches such as OScache when used in Cayenne? I was never 100% clear about how the old one interacted, and I guess nothing much had changed in this regard, but it would be good to understand this better.

* I see that version 2.0 will allow for pluggable eviction policies (They will switch between LRU and LIRS). And they mention the idea of weighting by key/value. Any thoughts about whether that would be useful to Cayenne to be able to implement even more flexible policies, particularly given the demise of OScache?


Ari

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Aristedes Maniatis
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