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https://issues.apache.org/jira/browse/JCR-863?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12498541
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Stefan Guggisberg commented on JCR-863:
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> Have looked into the other JIRA - on second look I am not sure if its a
> problem, as this uses lock() not tryLock, which is fail fast and exclusive. A
> bigger problem is the issue of JRE implementation on a given platform, not
> entirely sure how much this can be relied on.
the file locking issue discussed in JCR-912 and JCR-933 applies to both
FileChannel#lock() & FileChannel#tryLock():
A. as of java 1.6 the behaviour of lock() and tryLock() has changed. both
methods now consistently throw
an OverlappingFileLockException on all platforms if the the lock is already
held by the current process.
B. in java 1.4 & 1.5 lock() and tryLock() have a platform-dependant behaviour
if the lock is already held
by the current process::
on windows:
lock() blocks!
tryLock() returns null
on *nix:
lock() and tryLock() return a new FileLock object!
note that A. is the correct behaviour according to the javadoc.
since lock() doesn't always fail fast (it potentially blocks) i suggest using
tryLock() instead.
the suggested fix in JCR-933 addresses the incorrect & platform dependant
behaviour
described in B.
> Patch to use FileLock for locking instead of empty file
> -------------------------------------------------------
>
> Key: JCR-863
> URL: https://issues.apache.org/jira/browse/JCR-863
> Project: Jackrabbit
> Issue Type: Improvement
> Components: query
> Reporter: Michael Neale
> Fix For: 1.4
>
> Attachments: FSDirectory.patch, JCR-863.patch
>
>
> The FSDirectory uses File.createNewFile to effectively lock a directory (in
> makeLock), yet the Java Spec says explcitly not to use it for this purpose,
> and instead use FileLock from nio.
> The attached patch shows how this is/could be done (change is internal to the
> makeLock method only, and functionally equivalent, the same tests apply).
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