org.apache.cassandra.utils.concurrent

Class OpOrder.Barrier

java.lang.Object

org.apache.cassandra.utils.concurrent.OpOrder.Barrier

Enclosing class:

OpOrder

public final class OpOrder.Barrier
extends java.lang.Object

This class represents a synchronisation point providing ordering guarantees on operations started against the enclosing OpOrder. When issue() is called upon it (may only happen once per Barrier), the Barrier atomically partitions new operations from those already running (by expiring the current Group), and activates its isAfter() method which indicates if an operation was started before or after this partition. It offers methods to determine, or block until, all prior operations have finished, and a means to indicate to those operations that they are blocking forward progress. See OpOrder for idiomatic usage.

Constructor Summary

Constructors

Constructor and Description
Barrier()

Method Summary

Modifier and Type	Method and Description
boolean	allPriorOpsAreFinished()
void	await() wait for all operations started prior to issuing the barrier to complete
OpOrder.Group	getSyncPoint() returns the Group we are waiting on - any Group with .compareTo(getSyncPoint()) <= 0 must complete before await() returns
boolean	isAfter(OpOrder.Group group)
void	issue() Issues (seals) the barrier, meaning no new operations may be issued against it, and expires the current Group.
void	markBlocking() Mark all prior operations as blocking, potentially signalling them to more aggressively make progress
WaitQueue.Signal	register() Register to be signalled once allPriorOpsAreFinished() or allPriorOpsAreFinishedOrSafe() may return true

Methods inherited from class java.lang.Object

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

Constructor Detail

Barrier

public Barrier()

Method Detail

isAfter

public boolean isAfter(OpOrder.Group group)

Returns:

true if @param group was started prior to the issuing of the barrier. (Until issue is called, always returns true, but if you rely on this behavior you are probably Doing It Wrong.)

issue

public void issue()

Issues (seals) the barrier, meaning no new operations may be issued against it, and expires the current Group. Must be called before await() for isAfter() to be properly synchronised.

markBlocking

public void markBlocking()

Mark all prior operations as blocking, potentially signalling them to more aggressively make progress

register

public WaitQueue.Signal register()

Register to be signalled once allPriorOpsAreFinished() or allPriorOpsAreFinishedOrSafe() may return true

allPriorOpsAreFinished

public boolean allPriorOpsAreFinished()

Returns:

true if all operations started prior to barrier.issue() have completed

await

public void await()

wait for all operations started prior to issuing the barrier to complete

getSyncPoint

public OpOrder.Group getSyncPoint()

returns the Group we are waiting on - any Group with .compareTo(getSyncPoint()) <= 0 must complete before await() returns