com.bigdata.service.ndx.pipeline

Class KVOLatch

java.lang.Object

com.bigdata.util.concurrent.Latch

com.bigdata.service.ndx.pipeline.KVOLatch

Type Parameters:

K - The generic type of the user-defined key.

public class KVOLatch
extends Latch

A synchronization aid that allows one or more threads to await asynchronous writes on one or more scale-out indices. Once the counter reaches zero, all waiting threads are released. The counter is decremented automatically once a KVOC has been successfully written onto an index by an asynchronous write operation. This class may also be used as a synchronization aid independent of a KVOC

Since it is possible that the counter could be transiently zero as chunks are being added and drained concurrently, you MUST increment the counter before adding the first chunk and decrement the counter after adding the last chunk. Threads may invoke Latch.await() any time after the counter has been incremented. They will not be released until the counter is zero. If you have protected against transient zeros by pre-incrementing the counter, the threads will not be released until the asynchronous write operations are successfully completed.

The notification is based on KVOC, which associates an atomic counter and a user-defined key with each tuple. Notices are generated when the atomic counter is zero on decrement. Notices are aligned with the appropriate scope by creating an instance of the KVOScope with that scope and then pairing it with each KVOC.

Version:

$Id$

Author:

Bryan Thompson

See Also:

KVOC, IndexPartitionWriteTask, which is responsible for invoking {@link #dec()}.

Field Summary

Fields inherited from class com.bigdata.util.concurrent.Latch

log

Constructor Summary

Constructors

Constructor and Description
KVOLatch()

Method Summary

Methods inherited from class com.bigdata.util.concurrent.Latch

addAndGet, await, await, dec, get, inc, signal, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

KVOLatch

public KVOLatch()