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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-678) [PATCH] LockFactory implementation based on OS native locks (java.nio.*)
Date Wed, 18 Oct 2006 18:17:36 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-678?page=comments#action_12443323 ] 
            
Michael McCandless commented on LUCENE-678:
-------------------------------------------

I believe it's correct with the line in there (ie, as committed)?

That test case is verifying that the 2nd index writer indeed removes any leftover lockfiles
created by the first one.

It did not intend to test the case (but previously was) of opening an IndexWriter with create=true
while another IndexWriter is already open against that same directory.

> [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: Yonik Seeley
>            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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