akka.stream.stage

Class GraphStageLogic

java.lang.Object

akka.stream.stage.GraphStageLogic

Direct Known Subclasses:

ByteStringParser.ParsingLogic, GraphInterpreter.DownstreamBoundaryStageLogic, GraphInterpreter.UpstreamBoundaryStageLogic, GraphStageLogicWithLogging, KillSwitches.KillableGraphStageLogic, MergeHub.MergedSourceLogic, SupervisedGraphStageLogic, TcpConnectionStage.TcpStreamLogic, TimerGraphStageLogic

public abstract class GraphStageLogic
extends java.lang.Object

Represents the processing logic behind a GraphStage. Roughly speaking, a subclass of GraphStageLogic is a collection of the following parts: * A set of InHandler and OutHandler instances and their assignments to the Inlets and Outlets of the enclosing GraphStage * Possible mutable state, accessible from the InHandler and OutHandler callbacks, but not from anywhere else (as such access would not be thread-safe) * The lifecycle hooks preStart() and postStop() * Methods for performing stream processing actions, like pulling or pushing elements

The stage logic is completed once all its input and output ports have been closed. This can be changed by setting setKeepGoing to true.

The postStop lifecycle hook on the logic itself is called once all ports are closed. This is the only tear down callback that is guaranteed to happen, if the actor system or the materializer is terminated the handlers may never see any callbacks to onUpstreamFailure, onUpstreamFinish or onDownstreamFinish. Therefore stage resource cleanup should always be done in postStop.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	GraphStageLogic.ConditionalTerminateInput Input handler that terminates the state upon receiving completion if the given condition holds at that time.
static class	GraphStageLogic.ConditionalTerminateOutput Output handler that terminates the state upon receiving completion if the given condition holds at that time.
static class	GraphStageLogic.EagerTerminateInput$ Input handler that terminates the stage upon receiving completion.
static class	GraphStageLogic.EagerTerminateOutput$ Output handler that terminates the stage upon cancellation.
static class	GraphStageLogic.IgnoreTerminateInput$ Input handler that does not terminate the stage upon receiving completion.
static class	GraphStageLogic.IgnoreTerminateOutput$ Output handler that does not terminate the stage upon cancellation.
static class	GraphStageLogic.StageActor Minimal actor to work with other actors and watch them in a synchronous ways
static class	GraphStageLogic.StageActorRef$
static class	GraphStageLogic.StageActorRefNotInitializedException
static class	GraphStageLogic.StageActorRefNotInitializedException$
class	GraphStageLogic.SubSinkInlet<T> INTERNAL API
class	GraphStageLogic.SubSourceOutlet<T> INTERNAL API
static class	GraphStageLogic.TotallyIgnorantInput$ Input handler that does not terminate the stage upon receiving completion nor failure.

Constructor Summary

Constructors

Constructor and Description
GraphStageLogic(int inCount, int outCount)
GraphStageLogic(Shape shape)

Method Summary

Modifier and Type	Method and Description
protected void	abortEmitting(Outlet<?> out) Abort outstanding (suspended) emissions for the given outlet, if there are any.
protected void	abortReading(Inlet<?> in) Abort outstanding (suspended) reading for the given inlet, if there is any.
protected void	afterPostStop() INTERNAL API
protected void	beforePreStart() INTERNAL API
protected <T> void	cancel(Inlet<T> in) Requests to stop receiving events from a given input port.
protected <T> void	complete(Outlet<T> out) Signals that there will be no more elements emitted on the given port.
void	completeStage() Automatically invokes cancel() or complete() on all the input or output ports that have been called, then marks the stage as stopped.
protected InHandler	conditionalTerminateInput(scala.Function0<java.lang.Object> predicate) Input handler that terminates the state upon receiving completion if the given condition holds at that time.
protected OutHandler	conditionalTerminateOutput(scala.Function0<java.lang.Object> predicate) Output handler that terminates the state upon receiving completion if the given condition holds at that time.
protected <T> AsyncCallback<T>	createAsyncCallback(Procedure<T> handler) Java API: Obtain a callback object that can be used asynchronously to re-enter the current GraphStage with an asynchronous notification.
protected InHandler	eagerTerminateInput() Input handler that terminates the stage upon receiving completion.
protected OutHandler	eagerTerminateOutput() Output handler that terminates the stage upon cancellation.
protected <T> void	emit(Outlet<T> out, T elem) Emit an element through the given outlet, suspending execution if necessary.
protected <T> void	emit(Outlet<T> out, T elem, Effect andThen)
protected <T> void	emit(Outlet<T> out, T elem, scala.Function0<scala.runtime.BoxedUnit> andThen) Emit an element through the given outlet and continue with the given thunk afterwards, suspending execution if necessary.
protected <T> void	emitMultiple(Outlet<T> out, scala.collection.immutable.Iterable<T> elems) Emit a sequence of elements through the given outlet, suspending execution if necessary.
protected <T> void	emitMultiple(Outlet<T> out, scala.collection.immutable.Iterable<T> elems, scala.Function0<scala.runtime.BoxedUnit> andThen) Emit a sequence of elements through the given outlet and continue with the given thunk afterwards, suspending execution if necessary.
protected <T> void	emitMultiple(Outlet<T> out, java.util.Iterator<T> elems) Java API
protected <T> void	emitMultiple(Outlet<T> out, scala.collection.Iterator<T> elems) Emit a sequence of elements through the given outlet, suspending execution if necessary.
protected <T> void	emitMultiple(Outlet<T> out, java.util.Iterator<T> elems, Effect andThen) Java API
protected <T> void	emitMultiple(Outlet<T> out, scala.collection.Iterator<T> elems, scala.Function0<scala.runtime.BoxedUnit> andThen) Emit a sequence of elements through the given outlet and continue with the given thunk afterwards, suspending execution if necessary.
protected <T> void	fail(Outlet<T> out, java.lang.Throwable ex) Signals failure through the given port.
void	failStage(java.lang.Throwable ex) Automatically invokes cancel() or fail() on all the input or output ports that have been called, then marks the stage as stopped.
<T> AsyncCallback<T>	getAsyncCallback(scala.Function1<T,scala.runtime.BoxedUnit> handler) Obtain a callback object that can be used asynchronously to re-enter the current GraphStage with an asynchronous notification.
protected InHandler	getHandler(Inlet<?> in) Retrieves the current callback for the events on the given Inlet
protected OutHandler	getHandler(Outlet<?> out) Retrieves the current callback for the events on the given Outlet
protected GraphStageLogic.StageActor	getStageActor(scala.Function1<scala.Tuple2<ActorRef,java.lang.Object>,scala.runtime.BoxedUnit> receive) Initialize a StageActorRef which can be used to interact with from the outside world "as-if" an Actor.
protected <T> T	grab(Inlet<T> in) Once the callback InHandler.onPush() for an input port has been invoked, the element that has been pushed can be retrieved via this method.
java.lang.Object[]	handlers() INTERNAL API
protected <T> boolean	hasBeenPulled(Inlet<T> in) Indicates whether there is already a pending pull for the given input port.
protected InHandler	ignoreTerminateInput() Input handler that does not terminate the stage upon receiving completion.
protected OutHandler	ignoreTerminateOutput() Output handler that does not terminate the stage upon cancellation.
int	inCount()
GraphInterpreter	interpreter() INTERNAL API
protected <T> boolean	isAvailable(Inlet<T> in) Indicates whether there is an element waiting at the given input port.
<T> boolean	isAvailable(Outlet<T> out) Return true if the given output port is ready to be pushed.
protected <T> boolean	isClosed(Inlet<T> in) Indicates whether the port has been closed.
protected <T> boolean	isClosed(Outlet<T> out) Indicates whether the port has been closed.
protected Materializer	materializer() The Materializer that has set this GraphStage in motion.
int	outCount()
protected <Out,In extends Out> void	passAlong(Inlet<In> from, Outlet<Out> to, boolean doFinish, boolean doFail, boolean doPull) Install a handler on the given inlet that emits received elements on the given outlet before pulling for more data.
GraphInterpreter.Connection[]	portToConn() INTERNAL API
void	postStop() Invoked after processing of external events stopped because the stage is about to stop or fail.
void	preStart() Invoked before any external events are processed, at the startup of the stage.
protected <T> void	pull(Inlet<T> in) Requests an element on the given port.
protected <T> void	push(Outlet<T> out, T elem) Emits an element through the given output port.
protected <T> void	read(Inlet<T> in, scala.Function1<T,scala.runtime.BoxedUnit> andThen, scala.Function0<scala.runtime.BoxedUnit> onClose) Read an element from the given inlet and continue with the given function, suspending execution if necessary.
protected <T> void	read(Inlet<T> in, Procedure<T> andThen, Effect onClose) Java API: Read an element from the given inlet and continue with the given function, suspending execution if necessary.
protected <T> void	readN(Inlet<T> in, int n, scala.Function1<scala.collection.Seq<T>,scala.runtime.BoxedUnit> andThen, scala.Function1<scala.collection.Seq<T>,scala.runtime.BoxedUnit> onClose) Read a number of elements from the given inlet and continue with the given function, suspending execution if necessary.
protected <T> void	readN(Inlet<T> in, int n, Procedure<java.util.List<T>> andThen, Procedure<java.util.List<T>> onClose) Java API: Read a number of elements from the given inlet and continue with the given function, suspending execution if necessary.
protected void	setHandler(Inlet<?> in, InHandler handler) Assigns callbacks for the events for an Inlet
protected void	setHandler(Outlet<?> out, OutHandler handler) Assigns callbacks for the events for an Outlet
protected void	setHandlers(Inlet<?> in, Outlet<?> out, InHandler handler) Assign callbacks for linear stage for both Inlet and Outlet
protected void	setKeepGoing(boolean enabled) Controls whether this stage shall shut down when all its ports are closed, which is the default.
GraphStageLogic.StageActor	stageActor()
int	stageId() INTERNAL API
protected Materializer	subFusingMaterializer() An Materializer that may run fusable parts of the graphs that it materializes within the same actor as the current GraphStage (if fusing is available).
protected InHandler	totallyIgnorantInput() Input handler that does not terminate the stage upon receiving completion nor failure.
protected <T> void	tryPull(Inlet<T> in) Requests an element on the given port unless the port is already closed.

Methods inherited from class java.lang.Object

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

Constructor Detail

GraphStageLogic

public GraphStageLogic(int inCount,
                       int outCount)

GraphStageLogic

public GraphStageLogic(Shape shape)

Method Detail

inCount

public int inCount()

outCount

public int outCount()

stageId

public int stageId()

INTERNAL API

Returns:

(undocumented)

handlers

public java.lang.Object[] handlers()

INTERNAL API

Returns:

(undocumented)

portToConn

public GraphInterpreter.Connection[] portToConn()

INTERNAL API

Returns:

(undocumented)

interpreter

public GraphInterpreter interpreter()

INTERNAL API

Returns:

(undocumented)

materializer

protected Materializer materializer()

The Materializer that has set this GraphStage in motion.

Returns:

(undocumented)

subFusingMaterializer

protected Materializer subFusingMaterializer()

An Materializer that may run fusable parts of the graphs that it materializes within the same actor as the current GraphStage (if fusing is available). This materializer must not be shared outside of the GraphStage.

Returns:

(undocumented)

eagerTerminateInput

protected final InHandler eagerTerminateInput()

Input handler that terminates the stage upon receiving completion. The stage fails upon receiving a failure.

Returns:

(undocumented)

ignoreTerminateInput

protected final InHandler ignoreTerminateInput()

Input handler that does not terminate the stage upon receiving completion. The stage fails upon receiving a failure.

Returns:

(undocumented)

conditionalTerminateInput

protected final InHandler conditionalTerminateInput(scala.Function0<java.lang.Object> predicate)

Input handler that terminates the state upon receiving completion if the given condition holds at that time. The stage fails upon receiving a failure.

Parameters:

predicate - (undocumented)

Returns:

(undocumented)

totallyIgnorantInput

protected final InHandler totallyIgnorantInput()

Input handler that does not terminate the stage upon receiving completion nor failure.

Returns:

(undocumented)

eagerTerminateOutput

protected final OutHandler eagerTerminateOutput()

Output handler that terminates the stage upon cancellation.

Returns:

(undocumented)

ignoreTerminateOutput

protected final OutHandler ignoreTerminateOutput()

Output handler that does not terminate the stage upon cancellation.

Returns:

(undocumented)

conditionalTerminateOutput

protected final OutHandler conditionalTerminateOutput(scala.Function0<java.lang.Object> predicate)

Output handler that terminates the state upon receiving completion if the given condition holds at that time. The stage fails upon receiving a failure.

Parameters:

predicate - (undocumented)

Returns:

(undocumented)

setHandler

protected final void setHandler(Inlet<?> in,
                                InHandler handler)

Assigns callbacks for the events for an Inlet

Parameters:

in - (undocumented)

handler - (undocumented)

setHandlers

protected final void setHandlers(Inlet<?> in,
                                 Outlet<?> out,
                                 InHandler handler)

Assign callbacks for linear stage for both Inlet and Outlet

Parameters:

in - (undocumented)

out - (undocumented)

handler - (undocumented)

getHandler

protected final InHandler getHandler(Inlet<?> in)

Retrieves the current callback for the events on the given Inlet

Parameters:

in - (undocumented)

Returns:

(undocumented)

setHandler

protected final void setHandler(Outlet<?> out,
                                OutHandler handler)

Assigns callbacks for the events for an Outlet

Parameters:

out - (undocumented)

handler - (undocumented)

getHandler

protected final OutHandler getHandler(Outlet<?> out)

Retrieves the current callback for the events on the given Outlet

Parameters:

out - (undocumented)

Returns:

(undocumented)

pull

protected final <T> void pull(Inlet<T> in)

Requests an element on the given port. Calling this method twice before an element arrived will fail. There can only be one outstanding request at any given time. The method hasBeenPulled() can be used query whether pull is allowed to be called or not. This method will also fail if the port is already closed.

Parameters:

in - (undocumented)

tryPull

protected final <T> void tryPull(Inlet<T> in)

Requests an element on the given port unless the port is already closed. Calling this method twice before an element arrived will fail. There can only be one outstanding request at any given time. The method hasBeenPulled() can be used query whether pull is allowed to be called or not.

Parameters:

in - (undocumented)

cancel

protected final <T> void cancel(Inlet<T> in)

Requests to stop receiving events from a given input port. Cancelling clears any ungrabbed elements from the port.

Parameters:

in - (undocumented)

grab

protected final <T> T grab(Inlet<T> in)

Once the callback InHandler.onPush() for an input port has been invoked, the element that has been pushed can be retrieved via this method. After grab() has been called the port is considered to be empty, and further calls to grab() will fail until the port is pulled again and a new element is pushed as a response.

The method isAvailable() can be used to query if the port has an element that can be grabbed or not.

Parameters:

in - (undocumented)

Returns:

(undocumented)

hasBeenPulled

protected final <T> boolean hasBeenPulled(Inlet<T> in)

Indicates whether there is already a pending pull for the given input port. If this method returns true then isAvailable() must return false for that same port.

Parameters:

in - (undocumented)

Returns:

(undocumented)

isAvailable

protected final <T> boolean isAvailable(Inlet<T> in)

Indicates whether there is an element waiting at the given input port. grab() can be used to retrieve the element. After calling grab() this method will return false.

If this method returns true then hasBeenPulled() will return false for that same port.

Parameters:

in - (undocumented)

Returns:

(undocumented)

isClosed

protected final <T> boolean isClosed(Inlet<T> in)

Indicates whether the port has been closed. A closed port cannot be pulled.

Parameters:

in - (undocumented)

Returns:

(undocumented)

push

protected final <T> void push(Outlet<T> out,
                              T elem)

Emits an element through the given output port. Calling this method twice before a pull() has been arrived will fail. There can be only one outstanding push request at any given time. The method isAvailable() can be used to check if the port is ready to be pushed or not.

Parameters:

out - (undocumented)

elem - (undocumented)

setKeepGoing

protected final void setKeepGoing(boolean enabled)

Controls whether this stage shall shut down when all its ports are closed, which is the default. In order to have it keep going past that point this method needs to be called with a true argument before all ports are closed, and afterwards it will not be closed until this method is called with a false argument or the stage is terminated via completeStage() or failStage().

Parameters:

enabled - (undocumented)

complete

protected final <T> void complete(Outlet<T> out)

Signals that there will be no more elements emitted on the given port.

Parameters:

out - (undocumented)

fail

protected final <T> void fail(Outlet<T> out,
                              java.lang.Throwable ex)

Signals failure through the given port.

Parameters:

out - (undocumented)

ex - (undocumented)

completeStage

public final void completeStage()

Automatically invokes cancel() or complete() on all the input or output ports that have been called, then marks the stage as stopped.

failStage

public final void failStage(java.lang.Throwable ex)

Automatically invokes cancel() or fail() on all the input or output ports that have been called, then marks the stage as stopped.

Parameters:

ex - (undocumented)

isAvailable

public final <T> boolean isAvailable(Outlet<T> out)

Return true if the given output port is ready to be pushed.

Parameters:

out - (undocumented)

Returns:

(undocumented)

isClosed

protected final <T> boolean isClosed(Outlet<T> out)

Indicates whether the port has been closed. A closed port cannot be pushed.

Parameters:

out - (undocumented)

Returns:

(undocumented)

readN

protected final <T> void readN(Inlet<T> in,
                               int n,
                               scala.Function1<scala.collection.Seq<T>,scala.runtime.BoxedUnit> andThen,
                               scala.Function1<scala.collection.Seq<T>,scala.runtime.BoxedUnit> onClose)

Read a number of elements from the given inlet and continue with the given function, suspending execution if necessary. This action replaces the InHandler for the given inlet if suspension is needed and reinstalls the current handler upon receiving the last onPush() signal.

If upstream closes before N elements have been read, the onClose function is invoked with the elements which were read.

Parameters:

in - (undocumented)

n - (undocumented)

andThen - (undocumented)

onClose - (undocumented)

readN

protected final <T> void readN(Inlet<T> in,
                               int n,
                               Procedure<java.util.List<T>> andThen,
                               Procedure<java.util.List<T>> onClose)

Java API: Read a number of elements from the given inlet and continue with the given function, suspending execution if necessary. This action replaces the InHandler for the given inlet if suspension is needed and reinstalls the current handler upon receiving the last onPush() signal (before invoking the andThen function).

Parameters:

in - (undocumented)

n - (undocumented)

andThen - (undocumented)

onClose - (undocumented)

read

protected final <T> void read(Inlet<T> in,
                              scala.Function1<T,scala.runtime.BoxedUnit> andThen,
                              scala.Function0<scala.runtime.BoxedUnit> onClose)

Read an element from the given inlet and continue with the given function, suspending execution if necessary. This action replaces the InHandler for the given inlet if suspension is needed and reinstalls the current handler upon receiving the onPush() signal (before invoking the andThen function).

Parameters:

in - (undocumented)

andThen - (undocumented)

onClose - (undocumented)

read

protected final <T> void read(Inlet<T> in,
                              Procedure<T> andThen,
                              Effect onClose)

Java API: Read an element from the given inlet and continue with the given function, suspending execution if necessary. This action replaces the InHandler for the given inlet if suspension is needed and reinstalls the current handler upon receiving the onPush() signal (before invoking the andThen function).

Parameters:

in - (undocumented)

andThen - (undocumented)

onClose - (undocumented)

abortReading

protected final void abortReading(Inlet<?> in)

Abort outstanding (suspended) reading for the given inlet, if there is any. This will reinstall the replaced handler that was in effect before the read call.

Parameters:

in - (undocumented)

emitMultiple

protected final <T> void emitMultiple(Outlet<T> out,
                                      scala.collection.immutable.Iterable<T> elems,
                                      scala.Function0<scala.runtime.BoxedUnit> andThen)

Emit a sequence of elements through the given outlet and continue with the given thunk afterwards, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal (before invoking the andThen function).

Parameters:

out - (undocumented)

elems - (undocumented)

andThen - (undocumented)

emitMultiple

protected final <T> void emitMultiple(Outlet<T> out,
                                      scala.collection.immutable.Iterable<T> elems)

Emit a sequence of elements through the given outlet, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.

Parameters:

out - (undocumented)

elems - (undocumented)

emitMultiple

protected final <T> void emitMultiple(Outlet<T> out,
                                      java.util.Iterator<T> elems)

Java API

Emit a sequence of elements through the given outlet, suspending execution if necessary. This action replaces the AbstractOutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.

Parameters:

out - (undocumented)

elems - (undocumented)

emitMultiple

protected final <T> void emitMultiple(Outlet<T> out,
                                      java.util.Iterator<T> elems,
                                      Effect andThen)

Java API

Emit a sequence of elements through the given outlet, suspending execution if necessary. This action replaces the AbstractOutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.

Parameters:

out - (undocumented)

elems - (undocumented)

andThen - (undocumented)

emitMultiple

protected final <T> void emitMultiple(Outlet<T> out,
                                      scala.collection.Iterator<T> elems,
                                      scala.Function0<scala.runtime.BoxedUnit> andThen)

Emit a sequence of elements through the given outlet and continue with the given thunk afterwards, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal (before invoking the andThen function).

Parameters:

out - (undocumented)

elems - (undocumented)

andThen - (undocumented)

emitMultiple

protected final <T> void emitMultiple(Outlet<T> out,
                                      scala.collection.Iterator<T> elems)

Emit a sequence of elements through the given outlet, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.

Parameters:

out - (undocumented)

elems - (undocumented)

emit

protected final <T> void emit(Outlet<T> out,
                              T elem,
                              scala.Function0<scala.runtime.BoxedUnit> andThen)

Emit an element through the given outlet and continue with the given thunk afterwards, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal (before invoking the andThen function).

Parameters:

out - (undocumented)

elem - (undocumented)

andThen - (undocumented)

emit

protected final <T> void emit(Outlet<T> out,
                              T elem)

Emit an element through the given outlet, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.

Parameters:

out - (undocumented)

elem - (undocumented)

emit

protected final <T> void emit(Outlet<T> out,
                              T elem,
                              Effect andThen)

abortEmitting

protected final void abortEmitting(Outlet<?> out)

Abort outstanding (suspended) emissions for the given outlet, if there are any. This will reinstall the replaced handler that was in effect before the emit call.

Parameters:

out - (undocumented)

passAlong

protected final <Out,In extends Out> void passAlong(Inlet<In> from,
                                                    Outlet<Out> to,
                                                    boolean doFinish,
                                                    boolean doFail,
                                                    boolean doPull)

Install a handler on the given inlet that emits received elements on the given outlet before pulling for more data. doFinish and doFail control whether completion or failure of the given inlet shall lead to stage termination or not. doPull instructs to perform one initial pull on the from port.

Parameters:

from - (undocumented)

to - (undocumented)

doFinish - (undocumented)

doFail - (undocumented)

doPull - (undocumented)

getAsyncCallback

public final <T> AsyncCallback<T> getAsyncCallback(scala.Function1<T,scala.runtime.BoxedUnit> handler)

Obtain a callback object that can be used asynchronously to re-enter the current GraphStage with an asynchronous notification. The invoke() method of the returned AsyncCallback is safe to be called from other threads and it will in the background thread-safely delegate to the passed callback function. I.e. invoke() will be called by the external world and the passed handler will be invoked eventually in a thread-safe way by the execution environment.

This object can be cached and reused within the same GraphStageLogic.

Parameters:

handler - (undocumented)

Returns:

(undocumented)

createAsyncCallback

protected final <T> AsyncCallback<T> createAsyncCallback(Procedure<T> handler)

Java API: Obtain a callback object that can be used asynchronously to re-enter the current GraphStage with an asynchronous notification. The invoke() method of the returned AsyncCallback is safe to be called from other threads and it will in the background thread-safely delegate to the passed callback function. I.e. invoke() will be called by the external world and the passed handler will be invoked eventually in a thread-safe way by the execution environment.

This object can be cached and reused within the same GraphStageLogic.

Parameters:

handler - (undocumented)

Returns:

(undocumented)

stageActor

public final GraphStageLogic.StageActor stageActor()

getStageActor

protected final GraphStageLogic.StageActor getStageActor(scala.Function1<scala.Tuple2<ActorRef,java.lang.Object>,scala.runtime.BoxedUnit> receive)

Initialize a StageActorRef which can be used to interact with from the outside world "as-if" an Actor. The messages are looped through the getAsyncCallback mechanism of GraphStage so they are safe to modify internal state of this stage.

This method must (the earliest) be called after the GraphStageLogic constructor has finished running, for example from the preStart callback the graph stage logic provides.

Created StageActorRef to get messages and watch other actors in synchronous way.

The StageActorRef's lifecycle is bound to the Stage, in other words when the Stage is finished, the Actor will be terminated as well. The entity backing the StageActorRef is not a real Actor, but the GraphStageLogic itself, therefore it does not react to PoisonPill.

Parameters:

receive - callback that will be called upon receiving of a message by this special Actor

Returns:

minimal actor with watch method

beforePreStart

protected void beforePreStart()

INTERNAL API

afterPostStop

protected void afterPostStop()

INTERNAL API

preStart

public void preStart()
              throws java.lang.Exception

Invoked before any external events are processed, at the startup of the stage.

Throws:

java.lang.Exception

postStop

public void postStop()
              throws java.lang.Exception

Invoked after processing of external events stopped because the stage is about to stop or fail.

Throws:

java.lang.Exception