Class 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:
    • Constructor Detail

      • NativeFSLockFactory

        public NativeFSLockFactory()
        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!
      • NativeFSLockFactory

        public NativeFSLockFactory​(String lockDirName)
        Create a NativeFSLockFactory instance, storing lock files into the specified lockDirName:
        lockDirName - where lock files are created.
      • NativeFSLockFactory

        public NativeFSLockFactory​(File lockDir)
        Create a NativeFSLockFactory instance, storing lock files into the specified lockDir:
        lockDir - where lock files are created.
    • 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
        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
        lockName - name of the lock to be cleared.