Package org.apache.pekko.stream.stage

Class GraphStageLogic

java.lang.Object
org.apache.pekko.stream.stage.GraphStageLogic
Direct Known Subclasses:
GraphStageLogicWithLogging, KillSwitches.KillableGraphStageLogic, TimerGraphStageLogic
public abstract class GraphStageLogic extends 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 operator 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 operator resource cleanup should always be done in postStop.

  • Constructor Details

    • GraphStageLogic

      public GraphStageLogic(Shape shape)

  • Method Details

    • inCount

      public int inCount()

    • outCount

      public int outCount()

    • materializer

      protected Materializer materializer()
      The pekko.stream.Materializer that has set this GraphStage in motion.

      Can not be used from a GraphStage constructor. Access to materializer is provided by the pekko.stream.scaladsl.Source.fromMaterializer, pekko.stream.scaladsl.Flow.fromMaterializer and pekko.stream.scaladsl.Sink.fromMaterializer and their corresponding Java API factories.

    • subFusingMaterializer

      protected Materializer subFusingMaterializer()
      An pekko.stream.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.

    • eagerTerminateInput

      protected final InHandler eagerTerminateInput()
      Input handler that terminates the operator upon receiving completion. The operator fails upon receiving a failure.

    • ignoreTerminateInput

      protected final InHandler ignoreTerminateInput()
      Input handler that does not terminate the operator upon receiving completion. The operator fails upon receiving a failure.

    • conditionalTerminateInput

      protected final InHandler conditionalTerminateInput(scala.Function0<Object> predicate)
      Input handler that terminates the state upon receiving completion if the given condition holds at that time. The operator fails upon receiving a failure.

    • totallyIgnorantInput

      protected final InHandler totallyIgnorantInput()
      Input handler that does not terminate the operator upon receiving completion nor failure.

    • eagerTerminateOutput

      protected final OutHandler eagerTerminateOutput()
      Output handler that terminates the operator upon cancellation.

    • ignoreTerminateOutput

      protected final OutHandler ignoreTerminateOutput()
      Output handler that does not terminate the operator upon cancellation.

    • conditionalTerminateOutput

      protected final OutHandler conditionalTerminateOutput(scala.Function0<Object> predicate)
      Output handler that terminates the state upon receiving completion if the given condition holds at that time. The operator fails upon receiving a failure.

    • setHandler

      protected final void setHandler(Inlet<?> in, InHandler handler)
      Assigns callbacks for the events for an Inlet

    • setHandlers

      protected final void setHandlers(Inlet<?> in, Outlet<?> out, InHandler handler)
      Assign callbacks for linear operator for both Inlet and Outlet

    • getHandler

      protected final InHandler getHandler(Inlet<?> in)
      Retrieves the current callback for the events on the given Inlet

    • setHandler

      protected final void setHandler(Outlet<?> out, OutHandler handler)
      Assigns callbacks for the events for an Outlet

    • getHandler

      protected final OutHandler getHandler(Outlet<?> out)
      Retrieves the current callback for the events on the given Outlet

    • 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 <T>hasBeenPulled(org.apache.pekko.stream.Inlet<T>) can be used query whether pull is allowed to be called or not. This method will also fail if the port is already closed.

    • 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 <T>hasBeenPulled(org.apache.pekko.stream.Inlet<T>) can be used query whether pull is allowed to be called or not.

    • 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.

      If cancellation is due to an error, use cancel(in, cause) instead to propagate that cause upstream. This overload is a shortcut for cancel(in, SubscriptionWithCancelException.NoMoreElementsNeeded)

    • cancel

      protected final <T> void cancel(Inlet<T> in, Throwable cause)
      Requests to stop receiving events from a given input port. Cancelling clears any ungrabbed elements from the port.

    • 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 <T>grab(org.apache.pekko.stream.Inlet<T>) has been called the port is considered to be empty, and further calls to <T>grab(org.apache.pekko.stream.Inlet<T>) will fail until the port is pulled again and a new element is pushed as a response.

      The method <T>isAvailable(org.apache.pekko.stream.Inlet<T>) can be used to query if the port has an element that can be grabbed or not.

    • 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 <T>isAvailable(org.apache.pekko.stream.Inlet<T>) must return false for that same port.

    • isAvailable

      protected final <T> boolean isAvailable(Inlet<T> in)
      Indicates whether there is an element waiting at the given input port. <T>grab(org.apache.pekko.stream.Inlet<T>) can be used to retrieve the element. After calling <T>grab(org.apache.pekko.stream.Inlet<T>) this method will return false.

      If this method returns true then <T>hasBeenPulled(org.apache.pekko.stream.Inlet<T>) will return false for that same port.

    • isClosed

      protected final <T> boolean isClosed(Inlet<T> in)
      Indicates whether the port has been closed. A closed port cannot be pulled.

    • 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 <T>pull(org.apache.pekko.stream.Inlet<T>) has been arrived will fail. There can be only one outstanding push request at any given time. The method <T>isAvailable(org.apache.pekko.stream.Inlet<T>) can be used to check if the port is ready to be pushed or not.

    • setKeepGoing

      protected final void setKeepGoing(boolean enabled)
      Controls whether this operator 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 operator is terminated via completeStage() or failStage().

    • complete

      protected final <T> void complete(Outlet<T> out)
      Signals that there will be no more elements emitted on the given port.

    • fail

      protected final <T> void fail(Outlet<T> out, Throwable ex)
      Signals failure through the given port.

    • completeStage

      public final void completeStage()
      Automatically invokes <T>cancel(org.apache.pekko.stream.Inlet<T>) or <T>complete(org.apache.pekko.stream.Outlet<T>) on all the input or output ports that have been called, then marks the operator as stopped.

    • cancelStage

      public final void cancelStage(Throwable cause)
      Automatically invokes <T>cancel(org.apache.pekko.stream.Inlet<T>) or <T>complete(org.apache.pekko.stream.Outlet<T>) on all the input or output ports that have been called, then marks the stage as stopped.

    • failStage

      public final void failStage(Throwable ex)
      Automatically invokes <T>cancel(org.apache.pekko.stream.Inlet<T>) or <T>fail(org.apache.pekko.stream.Outlet<T>,java.lang.Throwable) on all the input or output ports that have been called, then marks the operator as stopped.

    • isAvailable

      public final <T> boolean isAvailable(Outlet<T> out)
      Return true if the given output port is ready to be pushed.

    • isClosed

      protected final <T> boolean isClosed(Outlet<T> out)
      Indicates whether the port has been closed. A closed port cannot be pushed.

    • readN

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

    • readN

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

    • 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).

    • 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).

    • 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.

    • 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).

    • 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.

    • emitMultiple

      protected final <T> void emitMultiple(Outlet<T> out, 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.

    • emitMultiple

      protected final <T> void emitMultiple(Outlet<T> out, 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.

    • 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).

    • emitMultiple

      protected final <T> void emitMultiple(Outlet<T> out, Spliterator<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).

      Since:
      1.2.0

    • 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.

    • 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).

    • 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.

    • 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.

    • 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 operator termination or not. doPull instructs to perform one initial pull on the from port.

    • passAlong$default$3

      protected final <Out, In extends Out> boolean passAlong$default$3()

    • passAlong$default$4

      protected final <Out, In extends Out> boolean passAlong$default$4()

    • passAlong$default$5

      protected final <Out, In extends Out> boolean passAlong$default$5()

    • 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 AsyncCallback.invoke method of the returned AsyncCallback is safe to be called from other threads. It will in the background thread-safely delegate to the passed callback function. I.e. AsyncCallback.invoke will be called by other thread and the passed handler will be invoked eventually in a thread-safe way by the execution environment.

      In case stream is not yet materialized AsyncCallback will buffer events until stream is available.

      AsyncCallback.invokeWithFeedback has an internal promise that will be failed if event cannot be processed due to stream completion.

      To be thread safe this method must only be called from either the constructor of the graph operator during materialization or one of the methods invoked by the graph operator machinery, such as onPush and onPull.

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

    • 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 AsyncCallback.invoke method of the returned AsyncCallback is safe to be called from other threads. It will in the background thread-safely delegate to the passed callback function. I.e. AsyncCallback.invoke will be called by other thread and the passed handler will be invoked eventually in a thread-safe way by the execution environment.

      AsyncCallback.invokeWithFeedback has an internal promise that will be failed if event cannot be processed due to stream completion.

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

    • stageActor

      public final GraphStageLogic.StageActor stageActor()

    • getStageActor

      protected final GraphStageLogic.StageActor getStageActor(scala.Function1<scala.Tuple2<ActorRef,Object>,scala.runtime.BoxedUnit> receive)
      Initialize a GraphStageLogic.StageActorRef which can be used to interact with from the outside world "as-if" an pekko.actor.Actor. The messages are looped through the <T>getAsyncCallback(scala.Function1<T,scala.runtime.BoxedUnit>) mechanism of GraphStage so they are safe to modify internal state of this operator.

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

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

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

      To be thread safe this method must only be called from either the constructor of the graph operator during materialization or one of the methods invoked by the graph operator machinery, such as onPush and onPull.

      Parameters:
      receive - callback that will be called upon receiving of a message by this special Actor
      Returns:
      minimal actor with watch method

    • getEagerStageActor

      protected GraphStageLogic.StageActor getEagerStageActor(Materializer eagerMaterializer, scala.Function1<scala.Tuple2<ActorRef,Object>,scala.runtime.BoxedUnit> receive)
      INTERNAL API

      To be thread safe this method must only be called from either the constructor of the graph operator during materialization or one of the methods invoked by the graph operator machinery, such as onPush and onPull.

    • stageActorName

      protected String stageActorName()
      Override and return a name to be given to the StageActor of this operator.

      This method will be only invoked and used once, during the first getStageActor(scala.Function1<scala.Tuple2<org.apache.pekko.actor.ActorRef,java.lang.Object>,scala.runtime.BoxedUnit>) invocation whichc reates the actor, since subsequent getStageActors calls function like become, rather than creating new actors.

      Returns an empty string by default, which means that the name will a unique generated String (e.g. "$$a").

    • beforePreStart

      protected void beforePreStart()
      INTERNAL API

    • afterPostStop

      protected void afterPostStop()
      INTERNAL API

    • preStart

      public void preStart() throws Exception
      Invoked before any external events are processed, at the startup of the operator.
      Throws:
      Exception

    • postStop

      public void postStop() throws Exception
      Invoked after processing of external events stopped because the operator is about to stop or fail.
      Throws:
      Exception

    • toString

      public String toString()
      Overrides:
      toString in class Object