[jira] [Commented] (OAK-2646) Look for alternative cache invalidation logic for better performance

["Chetan Mehrotra (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-2646?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14366637#comment-14366637 ] 

Chetan Mehrotra commented on OAK-2646:
--------------------------------------

Based on internal discussion [~tmueller] had following thoughts

{quote}
I would try a different heuristic. I have discussed this with Julian on the phone. One idea is, when reading a document, verify it is up to date by checking that all parents are up to date.

It _could_ turn out that this is a bit costly if there are many additional (cache-) accesses for each cache access (as many as there are parents). But it might not be a problem at all, we don't know that. If it turns out it's a problem, there are multiple possible solutions:

* Use a bloom filter for invalid documents (yeah bloom filter!), to avoid most cache accesses.

* Make documents "hierarchy aware". For each document, also keep the parent in memory, and add a direct, hard reference to it. That would be a bigger change I think, and the risk is to run out of memory, because some documents might not be correctly accounted for in the cache size calculation.
{quote}



> Look for alternative cache invalidation logic for better performance
> --------------------------------------------------------------------
>
>                 Key: OAK-2646
>                 URL: https://issues.apache.org/jira/browse/OAK-2646
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: mongomk
>            Reporter: Chetan Mehrotra
>             Fix For: 1.2
>
>
> Current cache invalidation logic has a higher cost. For e.g. in one of the deployment following log was seen
> {noformat}
> 12.03.2015 09:24:25.579 *INFO* [DocumentNodeStore background thread] org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore Background operations stats (clean:0, split:0, write:0, read:11848 ReadStats{cacheStats:InvalidationResult{invalidationCount=4, upToDateCount=286761, cacheSize=300411, timeTaken=10589, queryCount=654, cacheEntriesProcessedCount=138633}, head:1, cache:11842, dispatch:5, purge:0}
> {noformat}



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