org.apache.lucene.store
Class Lock

java.lang.Object
  org.apache.lucene.store.Lock

Direct Known Subclasses:

DbLock, JELock

public abstract class Lock
extends Object

An interprocess mutex lock.

Typical use might look like:

 new Lock.With(directory.makeLock("my.lock")) {
     public Object doBody() {
       ... code to execute while locked ...
     }
   }.run();
 

See Also:

Directory.makeLock(String)

Nested Class Summary

static class

Lock.With Utility class for executing code with exclusive access.

Field Summary

protected Throwable	failureReason If a lock obtain called, this failureReason may be set with the "root cause" Exception as to why the lock was not obtained.
static long	LOCK_OBTAIN_WAIT_FOREVER Pass this value to obtain(long) to try forever to obtain the lock.
static long	LOCK_POLL_INTERVAL How long obtain(long) waits, in milliseconds, in between attempts to acquire the lock.

Constructor Summary

Lock()

Method Summary

abstract boolean	isLocked() Returns true if the resource is currently locked.
abstract boolean	obtain() Attempts to obtain exclusive access and immediately return upon success or failure.
boolean	obtain(long lockWaitTimeout) Attempts to obtain an exclusive lock within amount of time given.
abstract void	release() Releases exclusive access.

Methods inherited from class java.lang.Object

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

Field Detail

LOCK_POLL_INTERVAL

public static long LOCK_POLL_INTERVAL

How long obtain(long) waits, in milliseconds, in between attempts to acquire the lock.

LOCK_OBTAIN_WAIT_FOREVER

public static final long LOCK_OBTAIN_WAIT_FOREVER

Pass this value to obtain(long) to try forever to obtain the lock.

See Also:

Constant Field Values

failureReason

protected Throwable failureReason

If a lock obtain called, this failureReason may be set with the "root cause" Exception as to why the lock was not obtained.

Constructor Detail

Lock

public Lock()

Method Detail

obtain

public abstract boolean obtain()
                        throws IOException

Attempts to obtain exclusive access and immediately return upon success or failure.

Returns:

true iff exclusive access is obtained

Throws:

IOException

obtain

public boolean obtain(long lockWaitTimeout)
               throws LockObtainFailedException,
                      IOException

Attempts to obtain an exclusive lock within amount of time given. Polls once per LOCK_POLL_INTERVAL (currently 1000) milliseconds until lockWaitTimeout is passed.

Parameters:

lockWaitTimeout - length of time to wait in milliseconds or LOCK_OBTAIN_WAIT_FOREVER to retry forever

Returns:

true if lock was obtained

Throws:

LockObtainFailedException - if lock wait times out

IllegalArgumentException - if lockWaitTimeout is out of bounds

IOException - if obtain() throws IOException

release

public abstract void release()
                      throws IOException

Releases exclusive access.

Throws:

IOException

isLocked

public abstract boolean isLocked()
                          throws IOException

Returns true if the resource is currently locked. Note that one must still call obtain() before using the resource.

Throws:

IOException