[infinispan-issues] [JBoss JIRA] (ISPN-1748) Allow consistency for concurrent updates when syncCommitPhase=false

[Mircea Markus (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-1748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12660594#comment-12660594 ] 

Mircea Markus edited comment on ISPN-1748 at 1/19/12 1:19 PM:
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after implementing this I've run some benchmarks and figures don't look at all encouraging.
The attached graph compares:
ispn50->async commit
ispn51->sync commit
ispn51c->this jira's implementation
Without performing an exhaustive analysis, the problem seem to be one of flow control:
without the fix in place we have the producer threads doing 2 sync RPCs (prepare and commit) and one async RPC performed by OOB (release locks). 
with the fix in place, we have the producer doing an 1 sync RPC(prepare) and then it triggers an OOB async thread that does 2 other RPCs.
Now the problem seems to be caused by the fact that the consumers create more requests than the OOB thread pool can handle, ending up in prepares waiting for locks to be released -> but locks are not released on time because OOB threads are exhausted. Increasing the OOB thread pool size might help.

The problem is more visible for REPL, because in that case the designated lock owner is the coordinator. What happens in the case of REPL is a very high percentage of timeouts on the coordinator and performance is very slow (I've interrupted the tests several times after 3h, normally it only takes about 30 mins). Again, the high number of timeouts indicates that locks are not being released on time, most likely because of the flow control.
                
      was (Author: mircea.markus):
    results of comparing:
ispn50->async commit
ispn51->sync commit
ispn51c->this jira's implementation
                  
> Allow consistency for concurrent updates when syncCommitPhase=false
> -------------------------------------------------------------------
>
>                 Key: ISPN-1748
>                 URL: https://issues.jboss.org/browse/ISPN-1748
>             Project: Infinispan
>          Issue Type: Enhancement
>          Components: Transactions
>    Affects Versions: 5.1.0.CR4
>            Reporter: Mircea Markus
>            Assignee: Mircea Markus
>              Labels: performace
>             Fix For: 5.1.0.FINAL
>
>         Attachments: All_PUT.png
>
>
> when syncCommitPhase=false then there is a window of inconsistency in the case multipel tx access the same key at the same time.
> This can be avoided by sending the lock release command after the commit command, in the same thread which is async triggered by the TM.commit. 
> This should be a very important performance buster for default configurations.

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