[LUCENE-635] [PATCH] Decouple locking implementation from Directory implementation

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.0.0
• Fix Version/s: 2.1
• Component/s: core/index
• Assignee: Yonik Seeley
• Reporter: Michael McCandless
• Created: 27/Jul/06 00:31
• Updated: 22/Nov/24 09:50
• Resolved: 29/Aug/06 01:12

Description

This is a spinoff of http://issues.apache.org/jira/browse/LUCENE-305.

I've opened this new issue to capture that it's wider scope than
LUCENE-305.

This is a patch originally created by Jeff Patterson (see above link)
and then modified as described here:

http://issues.apache.org/jira/browse/LUCENE-305#action_12418493

with some small additional changes:

• For each FSDirectory.getDirectory(), I made a corresponding
  version that also accepts a LockFactory instance. So, you can
  construct an FSDirectory with your own LockFactory.

• Cascaded defaulting for FSDirectory's LockFactory implementation:
  if you pass in a LockFactory instance, it's used; else if
  setDisableLocks was called, we use NoLockFactory; else, if the
  system property "org.apache.lucene.store.FSDirectoryLockFactoryClass"
  is defined, we use that; finally, we'll use the original locking
  implementation (SimpleFSLockFactory).

The gist is that all locking code has been moved out of *Directory and
into subclasses of a new abstract LockFactory class. You can now set
the LockFactory of a Directory to change how it does locking. For
example, you can create an FSDirectory but set its locking to
SingleInstanceLockFactory (if you know all writing/reading will take
place a single JVM).

The changes pass all unit tests (on Ubuntu Linux Sun Java 1.5 and
Windows XP Sun Java 1.4), and I added another TestCase to test the
LockFactory code.

Note that LockFactory defaults are not changed: FSDirectory defaults
to SimpleFSLockFactory and RAMDirectory defaults to
SingleInstanceLockFactory.

Next step (separate issue) is to create a LockFactory that uses the OS
native locks (through java.nio).

Issue Links

• is related to: LUCENE-305 [PATCH] Lock Framework - allows custom lock mechanism