Base class for Locking implementation. Directory uses instances of this class to
implement locking.
Lucene uses NativeFSLockFactory by default for FSDirectory-based index
directories.
Special care needs to be taken if you change the locking implementation: First be certain that
no writer is in fact writing to the index otherwise you can easily corrupt your index. Be sure to
do the LockFactory change on all Lucene instances and clean up all leftover lock files before
starting the new configuration for the first time. Different implementations can not work
together!
If you suspect that some LockFactory implementation is not working properly in your
environment, you can easily test it by using VerifyingLockFactory, LockVerifyServer and LockStressTest.