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From "Peter Dettman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-2674) FileDataStore ignores return code from setLastModified
Date Thu, 15 Jul 2010 11:11:53 GMT

    [ https://issues.apache.org/jira/browse/JCR-2674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12888777#action_12888777
] 

Peter Dettman commented on JCR-2674:
------------------------------------

1. My feeling is that "if (file.lastModified() < now + ACCESS_TIME_RESOLUTION)" is not
necessary, since the lastModified value will already be truncated to the system resolution,
but I do not think it is harmful.

2. I chose to throw exception only if file.canWrite, because I was trying to minimise the
impact of the change. It's not clear to me whether setLastModified might work when !file.canWrite.
However, it certainly must work (because of GC) if file.canWrite. I would consider moving
the canWrite test outside of the setLastModified call, similar to getRecordIfStored, it just
wasn't necessary to fix the immediate problem.

3. Well, not swallowed exactly, but caught and converted to failure return code (-1) e.g.
see BLOBInDataStore.getSize. In any case, the javadoc for Property.getLength/getLengths documents
-1 as a possible "failure" return code, so it had to be tested. I think if Property.getLength/getLengths
throws an exception, that is already correctly handled.

Thanks for the quick response.



> FileDataStore ignores return code from setLastModified
> ------------------------------------------------------
>
>                 Key: JCR-2674
>                 URL: https://issues.apache.org/jira/browse/JCR-2674
>             Project: Jackrabbit Content Repository
>          Issue Type: Bug
>          Components: jackrabbit-core
>    Affects Versions: 2.1.0
>         Environment: Solaris/ZFS/JDK1.6.0_20
>            Reporter: Peter Dettman
>            Assignee: Thomas Mueller
>            Priority: Critical
>             Fix For: 2.2.0
>
>         Attachments: JCR-2674.patch
>
>
> Garbage collection depends on the file modification date being successfully updated when
records are "touched" during the mark phase. The result of a silent failure is the catastrophic
loss of the file in the sweep phase.
> FileDataStore.getRecordIfStored does not, however, check the return code from setLastModified.
> I believe I was bitten by this when my dev deployment ran out of disk space. A substantial
portion of my datastore was deleted, and the best explanation I can come up with is that the
setLastModified calls started (silently) failing, leading to massive overkill in the sweep.
> There is also a call to setLastModified in FileDataStore.addRecord which is not strictly
correct in the face of GC (i.e. it needs the resolution offset, and also must succeed if the
file is writable or risk incorrect collection).
> Patch to follow.

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