org.apache.flink.streaming.runtime.tasks

Class StreamTask<OUT,OP extends StreamOperator<OUT>>

java.lang.Object

org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

org.apache.flink.streaming.runtime.tasks.StreamTask<OUT,OP>

Type Parameters:

OUT -

OP -

All Implemented Interfaces:

AsyncExceptionHandler

Direct Known Subclasses:

AbstractTwoInputStreamTask, MultipleInputStreamTask, OneInputStreamTask, SourceOperatorStreamTask, SourceStreamTask

@Internal
public abstract class StreamTask<OUT,OP extends StreamOperator<OUT>>
extends org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable
implements AsyncExceptionHandler

Base class for all streaming tasks. A task is the unit of local processing that is deployed and executed by the TaskManagers. Each task runs one or more StreamOperators which form the Task's operator chain. Operators that are chained together execute synchronously in the same thread and hence on the same stream partition. A common case for these chains are successive map/flatmap/filter tasks.

The task chain contains one "head" operator and multiple chained operators. The StreamTask is specialized for the type of the head operator: one-input and two-input tasks, as well as for sources, iteration heads and iteration tails.

The Task class deals with the setup of the streams read by the head operator, and the streams produced by the operators at the ends of the operator chain. Note that the chain may fork and thus have multiple ends.

The life cycle of the task is set up as follows:

 -- setInitialState -> provides state of all operators in the chain

 -- invoke()
       |
       +----> Create basic utils (config, etc) and load the chain of operators
       +----> operators.setup()
       +----> task specific init()
       +----> initialize-operator-states()
       +----> open-operators()
       +----> run()
       +----> close-operators()
       +----> dispose-operators()
       +----> common cleanup
       +----> task specific cleanup()
 

The StreamTask has a lock object called lock. All calls to methods on a StreamOperator must be synchronized on this lock object to ensure that no methods are called concurrently.

Field Summary

Fields

Modifier and Type	Field and Description
protected org.apache.flink.runtime.state.CheckpointStorage	checkpointStorage Our checkpoint storage.
protected StreamConfig	configuration The configuration of this streaming task.
protected StreamInputProcessor	inputProcessor The input processor.
protected static org.slf4j.Logger	LOG The logger used by the StreamTask and its subclasses.
protected MailboxProcessor	mailboxProcessor
protected OP	mainOperator the main operator that consumes the input streams of this task.
protected OperatorChain<OUT,OP>	operatorChain The chain of operators executed by this task.
protected org.apache.flink.runtime.state.StateBackend	stateBackend Our state backend.
protected TimerService	systemTimerService In contrast to timerService we should not register any user timers here.
protected TimerService	timerService The internal TimerService used to define the current processing time (default = System.currentTimeMillis()) and register timers for tasks to be executed in the future.
static ThreadGroup	TRIGGER_THREAD_GROUP The thread group that holds all trigger timer threads.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	StreamTask(org.apache.flink.runtime.execution.Environment env) Constructor for initialization, possibly with initial state (recovery / savepoint / etc).
protected	StreamTask(org.apache.flink.runtime.execution.Environment env, TimerService timerService) Constructor for initialization, possibly with initial state (recovery / savepoint / etc).
protected	StreamTask(org.apache.flink.runtime.execution.Environment environment, TimerService timerService, Thread.UncaughtExceptionHandler uncaughtExceptionHandler)
protected	StreamTask(org.apache.flink.runtime.execution.Environment environment, TimerService timerService, Thread.UncaughtExceptionHandler uncaughtExceptionHandler, StreamTaskActionExecutor actionExecutor) Constructor for initialization, possibly with initial state (recovery / savepoint / etc).
protected	StreamTask(org.apache.flink.runtime.execution.Environment environment, TimerService timerService, Thread.UncaughtExceptionHandler uncaughtExceptionHandler, StreamTaskActionExecutor actionExecutor, TaskMailbox mailbox)

Method Summary

Modifier and Type	Method and Description
void	abortCheckpointOnBarrier(long checkpointId, org.apache.flink.runtime.checkpoint.CheckpointException cause)
protected void	advanceToEndOfEventTime() Emits the MAX_WATERMARK so that all registered timers are fired.
protected void	afterInvoke()
void	cancel()
protected void	cancelTask()
protected void	cleanup()
protected void	cleanUpInvoke()
static <OUT> org.apache.flink.runtime.io.network.api.writer.RecordWriterDelegate<org.apache.flink.runtime.plugable.SerializationDelegate<StreamRecord<OUT>>>	createRecordWriterDelegate(StreamConfig configuration, org.apache.flink.runtime.execution.Environment environment)
StreamTaskStateInitializer	createStreamTaskStateInitializer()
protected void	declineCheckpoint(long checkpointId)
void	dispatchOperatorEvent(org.apache.flink.runtime.jobgraph.OperatorID operator, org.apache.flink.util.SerializedValue<org.apache.flink.runtime.operators.coordination.OperatorEvent> event)
protected void	finalize() The finalize method shuts down the timer.
protected void	finishTask() Instructs the task to go through its normal termination routine, i.e.
protected long	getAsyncCheckpointStartDelayNanos()
ExecutorService	getAsyncOperationsThreadPool()
org.apache.flink.core.fs.CloseableRegistry	getCancelables()
org.apache.flink.runtime.state.CheckpointStorageWorkerView	getCheckpointStorage()
protected CompletableFuture<Void>	getCompletionFuture()
StreamConfig	getConfiguration()
MailboxExecutorFactory	getMailboxExecutorFactory()
String	getName() Gets the name of the task, in the form "taskname (2/5)".
ProcessingTimeServiceFactory	getProcessingTimeServiceFactory()
StreamStatusMaintainer	getStreamStatusMaintainer()
void	handleAsyncException(String message, Throwable exception) Handles an exception thrown by another thread (e.g.
protected abstract void	init()
void	invoke()
boolean	isCanceled()
boolean	isFailing()
boolean	isMailboxLoopRunning()
boolean	isRunning()
boolean	isUsingNonBlockingInput()
Future<Void>	notifyCheckpointAbortAsync(long checkpointId)
Future<Void>	notifyCheckpointCompleteAsync(long checkpointId)
protected void	processInput(MailboxDefaultAction.Controller controller) This method implements the default action of the task (e.g.
void	restore()
void	runMailboxLoop()
boolean	runMailboxStep()
protected org.apache.flink.metrics.Counter	setupNumRecordsInCounter(StreamOperator streamOperator)
String	toString()
Future<Boolean>	triggerCheckpointAsync(org.apache.flink.runtime.checkpoint.CheckpointMetaData checkpointMetaData, org.apache.flink.runtime.checkpoint.CheckpointOptions checkpointOptions)
void	triggerCheckpointOnBarrier(org.apache.flink.runtime.checkpoint.CheckpointMetaData checkpointMetaData, org.apache.flink.runtime.checkpoint.CheckpointOptions checkpointOptions, org.apache.flink.runtime.checkpoint.CheckpointMetricsBuilder checkpointMetrics)

Methods inherited from class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

getCurrentNumberOfSubtasks, getEnvironment, getExecutionConfig, getIndexInSubtaskGroup, getJobConfiguration, getTaskConfiguration, getUserCodeClassLoader, setShouldInterruptOnCancel, shouldInterruptOnCancel

Methods inherited from class java.lang.Object

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

Field Detail

TRIGGER_THREAD_GROUP

public static final ThreadGroup TRIGGER_THREAD_GROUP

The thread group that holds all trigger timer threads.

LOG

protected static final org.slf4j.Logger LOG

The logger used by the StreamTask and its subclasses.

inputProcessor

@Nullable
protected StreamInputProcessor inputProcessor

The input processor. Initialized in init() method.

mainOperator

protected OP extends StreamOperator<OUT> mainOperator

the main operator that consumes the input streams of this task.

operatorChain

protected OperatorChain<OUT,OP extends StreamOperator<OUT>> operatorChain

The chain of operators executed by this task.

configuration

protected final StreamConfig configuration

The configuration of this streaming task.

stateBackend

protected final org.apache.flink.runtime.state.StateBackend stateBackend

Our state backend. We use this to create a keyed state backend.

checkpointStorage

protected final org.apache.flink.runtime.state.CheckpointStorage checkpointStorage

Our checkpoint storage. We use this to create checkpoint streams.

timerService

protected final TimerService timerService

The internal TimerService used to define the current processing time (default = System.currentTimeMillis()) and register timers for tasks to be executed in the future.

systemTimerService

protected final TimerService systemTimerService

In contrast to timerService we should not register any user timers here. It should be used only for system level timers.

mailboxProcessor

protected final MailboxProcessor mailboxProcessor

Constructor Detail

StreamTask

protected StreamTask(org.apache.flink.runtime.execution.Environment env)
              throws Exception

Constructor for initialization, possibly with initial state (recovery / savepoint / etc).

Parameters:

env - The task environment for this task.

Throws:

Exception

StreamTask

protected StreamTask(org.apache.flink.runtime.execution.Environment env,
                     @Nullable
                     TimerService timerService)
              throws Exception

Constructor for initialization, possibly with initial state (recovery / savepoint / etc).

Parameters:

env - The task environment for this task.

timerService - Optionally, a specific timer service to use.

Throws:

Exception

StreamTask

protected StreamTask(org.apache.flink.runtime.execution.Environment environment,
                     @Nullable
                     TimerService timerService,
                     Thread.UncaughtExceptionHandler uncaughtExceptionHandler)
              throws Exception

Throws:

Exception

StreamTask

protected StreamTask(org.apache.flink.runtime.execution.Environment environment,
                     @Nullable
                     TimerService timerService,
                     Thread.UncaughtExceptionHandler uncaughtExceptionHandler,
                     StreamTaskActionExecutor actionExecutor)
              throws Exception

Constructor for initialization, possibly with initial state (recovery / savepoint / etc).

This constructor accepts a special TimerService. By default (and if null is passes for the timer service) a DefaultTimerService will be used.

Parameters:

environment - The task environment for this task.

timerService - Optionally, a specific timer service to use.

uncaughtExceptionHandler - to handle uncaught exceptions in the async operations thread pool

actionExecutor - a mean to wrap all actions performed by this task thread. Currently, only SynchronizedActionExecutor can be used to preserve locking semantics.

Throws:

Exception

StreamTask

protected StreamTask(org.apache.flink.runtime.execution.Environment environment,
                     @Nullable
                     TimerService timerService,
                     Thread.UncaughtExceptionHandler uncaughtExceptionHandler,
                     StreamTaskActionExecutor actionExecutor,
                     TaskMailbox mailbox)
              throws Exception

Throws:

Exception

Method Detail

init

protected abstract void init()
                      throws Exception

Throws:

Exception

cancelTask

protected void cancelTask()
                   throws Exception

Throws:

Exception

cleanup

protected void cleanup()
                throws Exception

Throws:

Exception

processInput

protected void processInput(MailboxDefaultAction.Controller controller)
                     throws Exception

This method implements the default action of the task (e.g. processing one event from the input). Implementations should (in general) be non-blocking.

Parameters:

controller - controller object for collaborative interaction between the action and the stream task.

Throws:

Exception - on any problems in the action.

advanceToEndOfEventTime

protected void advanceToEndOfEventTime()
                                throws Exception

Emits the MAX_WATERMARK so that all registered timers are fired.

This is used by the source task when the job is TERMINATED. In the case, we want all the timers registered throughout the pipeline to fire and the related state (e.g. windows) to be flushed.

For tasks other than the source task, this method does nothing.

Throws:

Exception

finishTask

protected void finishTask()
                   throws Exception

Instructs the task to go through its normal termination routine, i.e. exit the run-loop and call StreamOperator.close() and StreamOperator.dispose() on its operators.

This is used by the source task to get out of the run-loop when the job is stopped with a savepoint.

For tasks other than the source task, this method does nothing.

Throws:

Exception

createStreamTaskStateInitializer

public StreamTaskStateInitializer createStreamTaskStateInitializer()

setupNumRecordsInCounter

protected org.apache.flink.metrics.Counter setupNumRecordsInCounter(StreamOperator streamOperator)

restore

public void restore()
             throws Exception

Overrides:

restore in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

Throws:

Exception

invoke

public final void invoke()
                  throws Exception

Specified by:

invoke in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

Throws:

Exception

runMailboxStep

@VisibleForTesting
public boolean runMailboxStep()
                                          throws Exception

Throws:

Exception

isMailboxLoopRunning

@VisibleForTesting
public boolean isMailboxLoopRunning()

runMailboxLoop

public void runMailboxLoop()
                    throws Exception

Throws:

Exception

afterInvoke

protected void afterInvoke()
                    throws Exception

Throws:

Exception

cleanUpInvoke

protected void cleanUpInvoke()
                      throws Exception

Throws:

Exception

getCompletionFuture

protected CompletableFuture<Void> getCompletionFuture()

cancel

public final void cancel()
                  throws Exception

Overrides:

cancel in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

Throws:

Exception

getMailboxExecutorFactory

public MailboxExecutorFactory getMailboxExecutorFactory()

isRunning

public final boolean isRunning()

isCanceled

public final boolean isCanceled()

isFailing

public final boolean isFailing()

finalize

protected void finalize()
                 throws Throwable

The finalize method shuts down the timer. This is a fail-safe shutdown, in case the original shutdown method was never called.

This should not be relied upon! It will cause shutdown to happen much later than if manual shutdown is attempted, and cause threads to linger for longer than needed.

Overrides:

finalize in class Object

Throws:

Throwable

getName

public final String getName()

Gets the name of the task, in the form "taskname (2/5)".

Returns:

The name of the task.

getCheckpointStorage

public org.apache.flink.runtime.state.CheckpointStorageWorkerView getCheckpointStorage()

getConfiguration

public StreamConfig getConfiguration()

getStreamStatusMaintainer

public StreamStatusMaintainer getStreamStatusMaintainer()

triggerCheckpointAsync

public Future<Boolean> triggerCheckpointAsync(org.apache.flink.runtime.checkpoint.CheckpointMetaData checkpointMetaData,
                                              org.apache.flink.runtime.checkpoint.CheckpointOptions checkpointOptions)

Overrides:

triggerCheckpointAsync in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

triggerCheckpointOnBarrier

public void triggerCheckpointOnBarrier(org.apache.flink.runtime.checkpoint.CheckpointMetaData checkpointMetaData,
                                       org.apache.flink.runtime.checkpoint.CheckpointOptions checkpointOptions,
                                       org.apache.flink.runtime.checkpoint.CheckpointMetricsBuilder checkpointMetrics)
                                throws IOException

Overrides:

triggerCheckpointOnBarrier in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

Throws:

IOException

abortCheckpointOnBarrier

public void abortCheckpointOnBarrier(long checkpointId,
                                     org.apache.flink.runtime.checkpoint.CheckpointException cause)
                              throws IOException

Overrides:

abortCheckpointOnBarrier in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

Throws:

IOException

declineCheckpoint

protected void declineCheckpoint(long checkpointId)

getAsyncOperationsThreadPool

public final ExecutorService getAsyncOperationsThreadPool()

notifyCheckpointCompleteAsync

public Future<Void> notifyCheckpointCompleteAsync(long checkpointId)

Overrides:

notifyCheckpointCompleteAsync in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

notifyCheckpointAbortAsync

public Future<Void> notifyCheckpointAbortAsync(long checkpointId)

Overrides:

notifyCheckpointAbortAsync in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

dispatchOperatorEvent

public void dispatchOperatorEvent(org.apache.flink.runtime.jobgraph.OperatorID operator,
                                  org.apache.flink.util.SerializedValue<org.apache.flink.runtime.operators.coordination.OperatorEvent> event)
                           throws org.apache.flink.util.FlinkException

Overrides:

dispatchOperatorEvent in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable

Throws:

org.apache.flink.util.FlinkException

getProcessingTimeServiceFactory

public ProcessingTimeServiceFactory getProcessingTimeServiceFactory()

handleAsyncException

public void handleAsyncException(String message,
                                 Throwable exception)

Handles an exception thrown by another thread (e.g. a TriggerTask), other than the one executing the main task by failing the task entirely.

In more detail, it marks task execution failed for an external reason (a reason other than the task code itself throwing an exception). If the task is already in a terminal state (such as FINISHED, CANCELED, FAILED), or if the task is already canceling this does nothing. Otherwise it sets the state to FAILED, and, if the invokable code is running, starts an asynchronous thread that aborts that code.

This method never blocks.

Specified by:

handleAsyncException in interface AsyncExceptionHandler

toString

public String toString()

Overrides:

toString in class Object

getCancelables

public final org.apache.flink.core.fs.CloseableRegistry getCancelables()

createRecordWriterDelegate

@VisibleForTesting
public static <OUT> org.apache.flink.runtime.io.network.api.writer.RecordWriterDelegate<org.apache.flink.runtime.plugable.SerializationDelegate<StreamRecord<OUT>>> createRecordWriterDelegate(StreamConfig configuration,
                                                                                                                                                                                                                  org.apache.flink.runtime.execution.Environment environment)

getAsyncCheckpointStartDelayNanos

protected long getAsyncCheckpointStartDelayNanos()

isUsingNonBlockingInput

public boolean isUsingNonBlockingInput()

Overrides:

isUsingNonBlockingInput in class org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable