[infinispan-issues] [JBoss JIRA] (ISPN-6706) Purging cache writers is [mostly] redundant when eviction is disabled and preload is enabled

William Burns (JIRA) issues at jboss.org
Wed May 25 09:10:00 EDT 2016


    [ https://issues.jboss.org/browse/ISPN-6706?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13242545#comment-13242545 ] 

William Burns commented on ISPN-6706:
-------------------------------------

Rereading what you wrote, I more understand your case.  I would like to ask some more information though.

You said the cluster is pausing due to the purge, this seems problematic of itself.  The purge shouldn't stop other concurrent operations and in most cases it will be very heavily IO bound so it shouldn't be taking up CPU.  How did the pause adversely affect your test?  Can you also provide your configuration?

> Purging cache writers is [mostly] redundant when eviction is disabled and preload is enabled
> --------------------------------------------------------------------------------------------
>
>                 Key: ISPN-6706
>                 URL: https://issues.jboss.org/browse/ISPN-6706
>             Project: Infinispan
>          Issue Type: Enhancement
>          Components: Loaders and Stores
>    Affects Versions: 8.2.2.Final
>            Reporter: Krzysztof Sobolewski
>
> This issue arised when I was testing a cluster with about 16 million entries. Our configuration is that all the data is also kept in memory, so eviction is disabled in this cache. But expiration is enabled. During the test I noticed pauses that started small but increased while the test was progressing, reaching more than 20 seconds at one point. After ruling out maintenance tasks in MySQL that could interfere, I discovered that the pause is caused by the expiration thread purging the database for expired entries. This was a huge and unnecessary drag so I hacked Infinispan to skip the purge of persistent state in cases when it's likely to be redundant with purging the transient state. I say "likely" because entries evicted maually via the evict() call poke a huge hole in the underlying assumptions :) Anyway, our cluster no longer regularly pauses for half a minute, so here's something for your consideration.



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