com.bigdata.resources
Class SplitTailTask

java.lang.Object
  com.bigdata.journal.AbstractTask<T>
      com.bigdata.resources.AbstractResourceManagerTask<T>
          com.bigdata.resources.AbstractPrepareTask
              com.bigdata.resources.SplitTailTask

All Implemented Interfaces:

ITask, Callable

public class SplitTailTask
extends AbstractPrepareTask

Splits the tail of an index partition and optionally submits a task to move the tail to a target data service specified by the caller.

The split point is choosen by locating the right-most non-leaf node. The key range which would enter that node is placed within the new right-sibling index partition. The rest of the key range is placed within the new left-sibling index partition.

The tail split operation is extremely fast since it only redefines the index partitions. However, it require RMI to the metadata index to do that and therefore should not be done during synchronous overflow in order to reduce the possibility for errors during that operation.

The right-sibling of tail split is a prime candidate for a move since there is an expectation that it will continue to be hot for writes. Therefore the caller has an opportunity when specifying a tail split to also specify that the new right-sibling index partition will be moved onto a caller specified data service.

Version:

$Id: SplitTailTask.java 2783 2010-05-07 13:14:20Z thompsonbry $

Author:

Bryan Thompson

TODO:

unit tests.

Nested Class Summary

Nested classes/interfaces inherited from class com.bigdata.journal.AbstractTask

AbstractTask.DelegateTask<T>, AbstractTask.InnerReadWriteTxServiceCallable, AbstractTask.InnerWriteServiceCallable<T>, AbstractTask.ResubmitException

Field Summary

Fields inherited from class com.bigdata.resources.AbstractResourceManagerTask

DEBUG, INFO, log, resourceManager

Fields inherited from class com.bigdata.journal.AbstractTask

checkpointNanoTime, concurrencyManager, isReadWriteTx, nanoTime_assignedWorker, nanoTime_beginWork, nanoTime_finishedWork, nanoTime_submitTask, readOnly, taskCounters, timestamp, transactionManager, tx

Constructor Summary

SplitTailTask(com.bigdata.resources.ViewMetadata vmd, UUID moveTarget)

Method Summary

protected void	clearRefs() Method is responsible for clearing the SoftReferences held by ViewMetadata for the source view(s) on the old journal.
protected Object	doTask() Implement the task behavior here.

Methods inherited from class com.bigdata.resources.AbstractResourceManagerTask

toString

Methods inherited from class com.bigdata.journal.AbstractTask

assertResource, assertRunning, assertUnisolated, call, clearLoggingContext, dropIndex, getCommitTime, getIndex, getJournal, getOnlyResource, getResource, getResourceManager, getTaskCounters, getTaskName, getTimestamp, isResource, registerIndex, setupLoggingContext, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

SplitTailTask

public SplitTailTask(com.bigdata.resources.ViewMetadata vmd,
                     UUID moveTarget)

Parameters:

vmd -

moveTarget - When non-null the new right-sibling (the tail) will be moved to the specified data service after the split.

Method Detail

clearRefs

protected void clearRefs()

Description copied from class: AbstractPrepareTask

Method is responsible for clearing the SoftReferences held by ViewMetadata for the source view(s) on the old journal.

Note: This method MUST be invoked in order to permit those references to be cleared more eagerly than the end of the entire asynchronous overflow operation (which is when the task references would themselves go out of scope and become available for GC).

Specified by:

clearRefs in class AbstractPrepareTask

doTask

protected Object doTask()
                 throws Exception

Description copied from class: AbstractTask

Implement the task behavior here.

Note: Long-running implementations MUST periodically test Thread.interrupted() and MUST throw an exception, such as InterruptedException, if they are interrupted. This behavior allows tasks to be canceled in a timely manner.

If you ignore or fail to test Thread.interrupted() then your task CAN NOT be aborted. If it is Future.cancel(boolean) with false then the task will run to completion even though it has been cancelled (but the Future will appear to have been cancelled).

If you simply return rather than throwing an exception then the WriteExecutorService will assume that your task completed and your (partial) results will be made restart-safe at the next commit!

Specified by:

doTask in class AbstractTask

Returns:

The object that will be returned by AbstractTask.call() iff the operation succeeds.

Throws:

Exception - The exception that will be thrown by AbstractTask.call() iff the operation fails.

InterruptedException - This exception SHOULD be thrown if Thread.interrupted() becomes true during execution.