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From "Alex Parvulescu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-2192) Concurrent commit during compaction results in mixed segments
Date Wed, 05 Nov 2014 19:29:35 GMT

    [ https://issues.apache.org/jira/browse/OAK-2192?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14198923#comment-14198923
] 

Alex Parvulescu commented on OAK-2192:
--------------------------------------

One observation on the _timestamp_ based cleanup approach: I've noticed that running compaction
against a fresh system (cold cache, only a subset of segments are loaded) will result in loading
all segmentsids with a really recent creation date (after the compaction start date) thanks
to the diff performed by the compaction process itself. 
this means that the first compaction run will double the size of the repo while not being
able to clean anything as nothing falls into the cleanup filter (segments older than a specific
time window).waiting for the cleanup window to pass and running compaction again will usually
help.

> Concurrent commit during compaction results in mixed segments
> -------------------------------------------------------------
>
>                 Key: OAK-2192
>                 URL: https://issues.apache.org/jira/browse/OAK-2192
>             Project: Jackrabbit Oak
>          Issue Type: Bug
>          Components: core
>            Reporter: Michael Dürig
>            Assignee: Michael Dürig
>              Labels: compaction, gc
>         Attachments: OAK-2192-2.patch, OAK-2192-poc-fix.patch, OAK-2192-possible-test.patch,
OAK-2192-v2.patch, OAK-2192-v3.patch, OAK-2192-v4.patch, OAK-2192-v5.patch, OAK-2192-v6.patch,
OAK-2192-v7.patch, OAK-2192.patch
>
>
> Changes that are committed during a segment store compaction run will be compacted on
top of the already compacted changes. However the compactor uses the wrong before state in
this case. Instead of compacting against the compacted before state it uses the un-compacted
before state. The resulting state will thus contain references to un-compacted state, making
those not eligible for later clean up. 



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