org.apache.hadoop.hbase.util

Class IdLock

java.lang.Object

org.apache.hadoop.hbase.util.IdLock

@InterfaceAudience.Private
public class IdLock
extends Object

Allows multiple concurrent clients to lock on a numeric id with a minimal memory overhead. The intended usage is as follows:

 IdLock.Entry lockEntry = idLock.getLockEntry(id);
 try {
   // User code.
 } finally {
   idLock.releaseLockEntry(lockEntry);
 }

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	IdLock.Entry An entry returned to the client as a lock object

Constructor Summary

Constructors

Constructor and Description
IdLock()

Method Summary

Modifier and Type	Method and Description
IdLock.Entry	getLockEntry(long id) Blocks until the lock corresponding to the given id is acquired.
boolean	isHeldByCurrentThread(long id) Test whether the given id is already locked by the current thread.
void	releaseLockEntry(IdLock.Entry entry) Must be called in a finally block to decrease the internal counter and remove the monitor object for the given id if the caller is the last client.
IdLock.Entry	tryLockEntry(long id, long time) Blocks until the lock corresponding to the given id is acquired.
void	waitForWaiters(long id, int numWaiters)

Methods inherited from class java.lang.Object

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

Constructor Detail

IdLock

public IdLock()

Method Detail

getLockEntry

public IdLock.Entry getLockEntry(long id)
                          throws IOException

Blocks until the lock corresponding to the given id is acquired.

Parameters:

id - an arbitrary number to lock on

Returns:

an "entry" to pass to releaseLockEntry(Entry) to release the lock

Throws:

IOException - if interrupted

tryLockEntry

public IdLock.Entry tryLockEntry(long id,
                                 long time)
                          throws IOException

Blocks until the lock corresponding to the given id is acquired.

Parameters:

id - an arbitrary number to lock on

time - time to wait in ms

Returns:

an "entry" to pass to releaseLockEntry(Entry) to release the lock

Throws:

IOException - if interrupted

releaseLockEntry

public void releaseLockEntry(IdLock.Entry entry)

Must be called in a finally block to decrease the internal counter and remove the monitor object for the given id if the caller is the last client.

Parameters:

entry - the return value of getLockEntry(long)

isHeldByCurrentThread

public boolean isHeldByCurrentThread(long id)

Test whether the given id is already locked by the current thread.

waitForWaiters

public void waitForWaiters(long id,
                           int numWaiters)
                    throws InterruptedException

Throws:

InterruptedException