Package com.complexible.common.curator.framework.locks

Class NonReentrantMutex

java.lang.Object

com.complexible.common.curator.framework.locks.NonReentrantMutex

All Implemented Interfaces:

InterProcessTxLock

public class NonReentrantMutex
extends Object
implements InterProcessTxLock

Since:

4.3

Author:

Scott Fines

Constructor Summary

Constructors

Constructor	Description
NonReentrantMutex(org.apache.curator.framework.CuratorFramework client, String path)
NonReentrantMutex(org.apache.curator.framework.CuratorFramework client, String path, org.apache.curator.framework.recipes.locks.LockInternalsDriver driver)

Method Summary

Modifier and Type	Method	Description
void	acquire(UUID theTxId)	Acquire the mutex - blocking until it's available.
boolean	acquire(UUID theTxId, long theTime, TimeUnit theTimeUnit)	Acquire the mutex - blocks until it's available or the given time expires.
protected byte[]	getLockNodeBytes()
Collection<String>	getParticipantNodes()	Return a sorted list of all current nodes participating in the lock
void	invalidateAll()	Discard any local record of held locks, without touching ZooKeeper.
boolean	isAcquired(UUID theTxId)
boolean	isHeldInProcess()	Whether this process holds the lock for any transaction, by its own records.
void	release(UUID theTxId)	Release the lock held for a transaction.
void	releaseAll()	Release all locks for all transactions that we've created.
boolean	releaseIfHeld(UUID theTxId)	Atomic, unlike the default implementation

Methods inherited from class java.lang.Object

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

Constructor Details

NonReentrantMutex

public NonReentrantMutex(org.apache.curator.framework.CuratorFramework client,
 String path)

Parameters:

client - client

path - the path to lock

NonReentrantMutex

public NonReentrantMutex(org.apache.curator.framework.CuratorFramework client,
 String path,
 org.apache.curator.framework.recipes.locks.LockInternalsDriver driver)

Parameters:

client - client

path - the path to lock

driver - lock driver

Method Details

acquire

public void acquire(UUID theTxId)
             throws Exception

Acquire the mutex - blocking until it's available. Each call to acquire must be balanced by a call to release(UUID)

Specified by:

acquire in interface InterProcessTxLock

Parameters:

theTxId -

Throws:

Exception - ZK errors, connection interruptions

acquire

public boolean acquire(UUID theTxId,
 long theTime,
 TimeUnit theTimeUnit)
                throws Exception

Acquire the mutex - blocks until it's available or the given time expires. Each call to acquire that returns true must be balanced by a call to release(UUID)

Specified by:

acquire in interface InterProcessTxLock

Parameters:

theTxId -

theTime - time to wait

theTimeUnit - time unit

Returns:

true if the mutex was acquired, false if not

Throws:

Exception - ZK errors, connection interruptions

isAcquired

public boolean isAcquired(UUID theTxId)

Specified by:

isAcquired in interface InterProcessTxLock

Parameters:

theTxId - the transaction id to check

Returns:

true if there is a lock for the specified transaction id.

isHeldInProcess

public boolean isHeldInProcess()

Description copied from interface: InterProcessTxLock

Whether this process holds the lock for any transaction, by its own records. The default reports false; implementations that record locks must override it.

Specified by:

isHeldInProcess in interface InterProcessTxLock

releaseAll

public void releaseAll()
                throws Exception

Release all locks for all transactions that we've created.

Every lock is attempted even if some fail -- leaving the rest held is worse than a partial failure. The first failure is thrown at the end, the others suppressed.

Specified by:

releaseAll in interface InterProcessTxLock

Throws:

Exception

invalidateAll

public void invalidateAll()

Discard any local record of held locks, without touching ZooKeeper.

Called when this node's ZooKeeper session is lost. Lock nodes are ephemeral, so the session ending is itself the release -- unlike InterProcessTxLock.releaseAll(), there is nothing left to delete.

The default does nothing. Implementations that cache lock state must override it.

Without this, isAcquired(java.util.UUID) keeps answering true for locks ZooKeeper released with the session, and a joining node can take the exclusive lease while a transaction believes it is protected.

Discards lock state created by a previous Curator session. LOST is queued and delivered on Curator's dispatch thread, so the connection may be already repaired by the time we see it. Comparing indices errs in one direction only: a lock granted by the live connection always carries the current index and is kept, while one recorded against an older connection is dropped.

Best-effort: Curator drops queued state events when its 25-slot queue overflows, so a LOST may never reach us at all.

Specified by:

invalidateAll in interface InterProcessTxLock

release

public void release(UUID theTxId)
             throws Exception

Release the lock held for a transaction.

Specified by:

release in interface InterProcessTxLock

Parameters:

theTxId -

Throws:

IllegalMonitorStateException - if we hold no lock for this transaction

Exception

releaseIfHeld

public boolean releaseIfHeld(UUID theTxId)
                      throws Exception

Atomic, unlike the default implementation

Specified by:

releaseIfHeld in interface InterProcessTxLock

Returns:

true if the lock was held and is now released

Throws:

Exception

getParticipantNodes

public Collection<String> getParticipantNodes()
                                       throws IOException

Return a sorted list of all current nodes participating in the lock

Returns:

list of nodes

Throws:

IOException - ZK errors, interruptions, etc.

getLockNodeBytes

protected byte[] getLockNodeBytes()