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Posted to oak-issues@jackrabbit.apache.org by "Michael Dürig (JIRA)" <ji...@apache.org> on 2015/12/11 12:27:11 UTC

[jira] [Updated] (OAK-3055) Improve segment cache in SegmentTracker

     [ https://issues.apache.org/jira/browse/OAK-3055?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Michael Dürig updated OAK-3055:
-------------------------------
    Labels: candidate_oak_1_0 candidate_oak_1_2 doc-impacting resilience scalability  (was: doc-impacting resilience scalability)

> Improve segment cache in SegmentTracker
> ---------------------------------------
>
>                 Key: OAK-3055
>                 URL: https://issues.apache.org/jira/browse/OAK-3055
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: segmentmk
>            Reporter: Michael Dürig
>            Assignee: Michael Dürig
>              Labels: candidate_oak_1_0, candidate_oak_1_2, doc-impacting, resilience, scalability
>             Fix For: 1.3.3
>
>         Attachments: OAK-3055.patch
>
>
> The hand crafted segment cache in {{SegmentTracker}} is prone to lock contentions in concurrent access scenarios. As {{SegmentNodeStore#merge}} might also end up acquiring this lock while holding the commit semaphore the situation can easily lead to many threads being blocked on the commit semaphore. The {{SegmentTracker}} cache doesn't differentiate between read and write access, which means that reader threads can block writer threads. 



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