[ http://issues.apache.org/jira/browse/LUCENE-678?page=all ]
Michael McCandless reopened LUCENE-678:
---------------------------------------
Assignee: Michael McCandless (was: Yonik Seeley)
> [PATCH] LockFactory implementation based on OS native locks (java.nio.*)
> ------------------------------------------------------------------------
>
> Key: LUCENE-678
> URL: http://issues.apache.org/jira/browse/LUCENE-678
> Project: Lucene - Java
> Issue Type: New Feature
> Components: Store
> Affects Versions: 2.1
> Reporter: Michael McCandless
> Assigned To: Michael McCandless
> Priority: Minor
> Fix For: 2.0.1
>
> Attachments: LUCENE-678-patch.txt
>
>
> The current default locking for FSDirectory is SimpleFSLockFactory.
> It uses java.io.File.createNewFile for its locking, which has this
> spooky warning in Sun's javadocs:
> Note: this method should not be used for file-locking, as the
> resulting protocol cannot be made to work reliably. The FileLock
> facility should be used instead.
> So, this patch provides a LockFactory implementation based on FileLock
> (using java.nio.*).
> All unit tests pass with this patch, on OS X (10.4.8), Linux (Ubuntu
> 6.06), and Windows XP SP2.
> Another benefit of native locks is the OS automatically frees them if
> the JVM exits before Lucene can free its locks. Many people seem to
> hit this (old lock files still on disk) now.
> I've created this new class:
> org.apache.lucene.store.NativeFSLockFactory
> and added a couple test cases to the existing TestLockFactory.
> I've left SimpleFSLockFactory as the default locking for FSDirectory
> for now. I think we should get some usage / experience with
> NativeFSLockFactory and then later on make it the default locking
> implementation?
> I also tested changing FSDirectory's default locking to
> NativeFSLockFactory and all unit tests still pass (on the above
> platforms).
> One important note about locking over NFS: some NFS servers and/or
> clients do not support it, or, it's a configuration option or mode
> that must be explicitly enabled. When it's misconfigured it's able to
> take a long time (35 seconds in my case) before throwing an exception.
> To handle this, I acquire & release a random test lock on creating the
> NativeFSLockFactory to verify locking is configured properly.
> A few other small changes in the patch:
> - Added a "failure reason" to Lock.java so that in
> obtain(lockWaitTimeout), if there is a persistent IOException
> in trying to obtain the lock, this can be messaged & included in
> the "Lock obtain timed out" that's raised.
> - Corrected javadoc in SimpleFSLockFactory: it previously said the
> wrong system property for overriding lock class via system
> properties
> - Fixed unhandled IOException when opening an IndexWriter for
> create, if the locks dir does not exist (just added
> lockDir.exists() check in clearAllLocks method of
> SimpleFSLockFactory & NativeFSLockFactory.
> - Fixed a few small unrelated issues with TestLockFactory, and
> also fixed tests to accept NativeFSLockFactory as the default
> locking implementation for FSDirectory.
> - Fixed a typo in javadoc in FieldsReader.java
> - Added some more javadoc for the LockFactory.setLockPrefix
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