com.bigdata.journal
Interface ITask<T>

All Superinterfaces:

Callable<T>

All Known Implementing Classes:

AbstractAtomicUpdateTask, AbstractPrepareTask, AbstractResourceManagerTask, AbstractTask, AbstractTask.DelegateTask, AbstractTask.InnerReadWriteTxServiceCallable, AbstractTask.InnerWriteServiceCallable, CompactingMergeTask, CompactingMergeTask.AtomicUpdateCompactingMergeTask, DataService.GetIndexMetadataTask, DataService.RangeIteratorTask, DropIndexTask, IncrementalBuildTask, IncrementalBuildTask.AtomicUpdateIncrementalBuildTask, IndexProcedureTask, JoinIndexPartitionTask, JoinIndexPartitionTask.AtomicUpdateJoinIndexPartition, JournalTransactionService.SinglePhaseCommit, MetadataService.DropScaleOutIndexTask, MetadataService.JoinIndexPartitionTask, MetadataService.MoveIndexPartitionTask, MetadataService.NextPartitionIdTask, MetadataService.RegisterScaleOutIndexTask, MetadataService.SplitIndexPartitionTask, MoveTask, MoveTask.AtomicUpdate, RegisterIndexTask, ScatterSplitTask, SplitIndexPartitionTask, SplitIndexPartitionTask.AtomicUpdateSplitIndexPartitionTask, SplitTailTask, SplitUtility.BuildIndexSegmentSplitTask

public interface ITask<T>
extends Callable<T>

Interface available to tasks running under the ConcurrencyManager.

Version:

$Id: ITask.java 2265 2009-10-26 12:51:06Z thompsonbry $

Author:

Bryan Thompson

Method Summary

IIndex	getIndex(String name) Return an appropriate view of the named index for the operation.
IJournal	getJournal() The journal against which the operation will be carried out.
String	getOnlyResource() Return the only declared resource.
String[]	getResource() Returns a copy of the array of resources declared to the constructor.
IResourceManager	getResourceManager() The object used to manage access to the resources from which views of the indices are created.
TaskCounters	getTaskCounters() The object used to track events and times for the task.
String	toString() Returns Task{taskName,timestamp,resource[]}

Methods inherited from interface java.util.concurrent.Callable

call

Method Detail

getResourceManager

IResourceManager getResourceManager()

The object used to manage access to the resources from which views of the indices are created.

getJournal

IJournal getJournal()

The journal against which the operation will be carried out.

If the task is running against an ITx.UNISOLATED index, then this will be the IResourceManager.getLiveJournal(). If the operation is a historical read, then it will be whatever journal is appropriate to the historical commit point against which the task is being run.

Note: For ITx.UNISOLATED operations this exposes unconstrained access to the journal that could be used to violate the concurrency control mechanisms, therefore you SHOULD NOT use this unless you have a clear idea what you are about. You should be able to write all application level tasks in terms of getIndex(String) and operations on the returned index.

Note: For example, if you use the returned object to access a named index and modify the state of that named index, your changes WILL NOT be noticed by the checkpoint protocol in AbstractTask.InnerWriteServiceCallable.

Returns:

The corresponding journal for that timestamp -or- null if no journal has data for that timestamp, including when a historical journal with data for that timestamp has been deleted.

See Also:

IResourceManager.getJournal(long)

getResource

String[] getResource()

Returns a copy of the array of resources declared to the constructor.

getOnlyResource

String getOnlyResource()

Return the only declared resource.

Returns:

The declared resource.

Throws:

IllegalStateException - if more than one resource was declared.

toString

String toString()

Returns Task{taskName,timestamp,resource[]}

Overrides:

toString in class Object

getIndex

IIndex getIndex(String name)

Return an appropriate view of the named index for the operation.

When the task is isolated by a transaction, then the index will be isolated by the transaction using the appropriate isolation level. If the transaction is read-only, then the index will not be writable.

When the task is a read-only unisolated operation, the index will be read-only and will read from the most recent committed state of the store prior to the time at which the task began to execute. If multiple index views are requested they will all use the same committed state of the store.

When the task is an unisolated write operation the index will be the unisolated writable (aka "live" or "current" index). Access to the unisolated writable indices is single-threaded. This constraint is enforced by a lock system using the named resources declared in the task constructor.

Parameters:

name - The index name.

Returns:

An appropriate view of the named index.

Throws:

NoSuchIndexException - if the named index does not exist at the time that the operation is executed.

StaleLocatorException - if the named index does not exist at the time the operation is executed and the IResourceManager has information which indicates that the index partition has been split, joined or moved.

IllegalStateException - if the named index is not one of the resources declared to the constructor.

getTaskCounters

TaskCounters getTaskCounters()

The object used to track events and times for the task.