kafka-streams-internals-Task.adoc

Task Contract — Stream Processor Tasks

Task is the abstraction of stream processor tasks.

Table 1. Task Contract

Method	Description
applicationId	String applicationId() Application ID of the Kafka Streams application the task belongs to
changelogPartitions	Collection<TopicPartition> changelogPartitions() Changelog partitions associated with the task Used when: AssignedStreamsTasks is requested to updateRestored and addToRestoring AssignedTasks is requested to mark a task as ready for execution and processing records StreamTask is requested to initialize state stores
close	void close( boolean clean, boolean isZombie) Closes the task Used when: AssignedTasks is requested to closeNonRunningTasks, suspendTasks, closeZombieTask, close, and closeUnclean StandbyTask is requested to closeSuspended
closeSuspended	void closeSuspended( boolean clean, boolean isZombie, RuntimeException e) Used when: AssignedTasks is requested to closeNonAssignedSuspendedTasks StreamTask is requested to close
commit	void commit() Commits the task Used when: AssignedStreamsTasks is requested to maybeCommitPerUserRequested AssignedTasks is requested to commit StandbyTask is requested to close
commitNeeded	boolean commitNeeded() Used when: AssignedStreamsTasks is requested to maybeCommitPerUserRequested AssignedTasks is requested to commit
context	ProcessorContext context() ProcessorContext of the task
getStore	StateStore getStore(String name) Looks up the state store by name Used exclusively when StreamThreadStateStoreProvider is requested for the stores
hasStateStores	boolean hasStateStores()
id	TaskId id() TaskId of the task
initializeStateStores	boolean initializeStateStores() Initializes state stores (of the ProcessorTopology) Enabled (true) if the task has no state stores that need restoring. StandbyTask always returns true Used exclusively when AssignedTasks is requested to initialize new tasks
initializeTopology	void initializeTopology() Initializes the topology of processor nodes Used exclusively when AssignedTasks is requested to mark the specified task as ready for execution and processing records
partitions	Set<TopicPartition> partitions() Used when: AssignedStreamsTasks is requested to addToRestoring AssignedTasks is requested to maybeResumeSuspendedTask, transitionToRunning, and closeNonAssignedSuspendedTasks StreamThread is requested to updateThreadMetadata
resume	void resume() Resumes the task Used exclusively when AssignedTasks is requested to attempt to resume suspended task (when the task has actually been suspended)
suspend	void suspend() Suspends the task Used exclusively when AssignedTasks is requested to suspend tasks.
topology	ProcessorTopology topology() ProcessorTopology of the task
toString	String toString(String indent) Describes the task (textual representation)

Note	AbstractTask is the base implementation of the Task Contract in Kafka Streams (with StandbyTask and StreamTask as the only concrete implementations).