org.apache.lucene.store
Class NativeFSLockFactory

java.lang.Object
  org.apache.lucene.store.LockFactory
      org.apache.lucene.store.FSLockFactory
          org.apache.lucene.store.NativeFSLockFactory

public class NativeFSLockFactory
extends FSLockFactory

Implements LockFactory using native OS file locks. Note that because this LockFactory relies on java.nio.* APIs for locking, any problems with those APIs will cause locking to fail. Specifically, on certain NFS environments the java.nio.* locks will fail (the lock can incorrectly be double acquired) whereas SimpleFSLockFactory worked perfectly in those same environments. For NFS based access to an index, it's recommended that you try SimpleFSLockFactory first and work around the one limitation that a lock file could be left when the JVM exits abnormally.

The primary benefit of NativeFSLockFactory is that lock files will be properly removed (by the OS) if the JVM has an abnormal exit.

Note that, unlike SimpleFSLockFactory, the existence of leftover lock files in the filesystem on exiting the JVM is fine because the OS will free the locks held against these files even though the files still remain.

If you suspect that this or any other LockFactory is not working properly in your environment, you can easily test it by using VerifyingLockFactory, LockVerifyServer and LockStressTest.

See Also:

LockFactory

Field Summary

Fields inherited from class org.apache.lucene.store.FSLockFactory

lockDir

Fields inherited from class org.apache.lucene.store.LockFactory

lockPrefix

Constructor Summary

NativeFSLockFactory()
Create a NativeFSLockFactory instance, with null (unset) lock directory.

NativeFSLockFactory(File lockDir)
Create a NativeFSLockFactory instance, storing lock files into the specified lockDir:

NativeFSLockFactory(String lockDirName)
Create a NativeFSLockFactory instance, storing lock files into the specified lockDirName:

Method Summary

void	clearLock(String lockName) Attempt to clear (forcefully unlock and remove) the specified lock.
Lock	makeLock(String lockName) Return a new Lock instance identified by lockName.

Methods inherited from class org.apache.lucene.store.FSLockFactory

getLockDir, setLockDir

Methods inherited from class org.apache.lucene.store.LockFactory

getLockPrefix, setLockPrefix

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NativeFSLockFactory

public NativeFSLockFactory()
                    throws IOException

Create a NativeFSLockFactory instance, with null (unset) lock directory. When you pass this factory to a FSDirectory subclass, the lock directory is automatically set to the directory itself. Be sure to create one instance for each directory your create!

Throws:

IOException

NativeFSLockFactory

public NativeFSLockFactory(String lockDirName)
                    throws IOException

Create a NativeFSLockFactory instance, storing lock files into the specified lockDirName:

Parameters:

lockDirName - where lock files are created.

Throws:

IOException

NativeFSLockFactory

public NativeFSLockFactory(File lockDir)
                    throws IOException

Create a NativeFSLockFactory instance, storing lock files into the specified lockDir:

Parameters:

lockDir - where lock files are created.

Throws:

IOException

Method Detail

makeLock

public Lock makeLock(String lockName)

Description copied from class: LockFactory

Return a new Lock instance identified by lockName.

Specified by:

makeLock in class LockFactory

Parameters:

lockName - name of the lock to be created.

clearLock

public void clearLock(String lockName)
               throws IOException

Description copied from class: LockFactory

Attempt to clear (forcefully unlock and remove) the specified lock. Only call this at a time when you are certain this lock is no longer in use.

Specified by:

clearLock in class LockFactory

Parameters:

lockName - name of the lock to be cleared.

Throws:

IOException