// #timed
// each time an event is pushed through it will trigger a period of silence
public class TimedGate<A> extends GraphStage<FlowShape<A, A>> {
private final FiniteDuration silencePeriod;
public TimedGate(FiniteDuration silencePeriod) {
this.silencePeriod = silencePeriod;
}
public final Inlet<A> in = Inlet.create("TimedGate.in");
public final Outlet<A> out = Outlet.create("TimedGate.out");
private final FlowShape<A, A> shape = FlowShape.of(in, out);
@Override
public FlowShape<A, A> shape() {
return shape;
}
@Override
public GraphStageLogic createLogic(Attributes inheritedAttributes) {
return new TimerGraphStageLogic(shape) {
private boolean open = false;
{
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
A elem = grab(in);
if (open) pull(in);
else {
push(out, elem);
open = true;
scheduleOnce("key", silencePeriod);
}
}
});
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
pull(in);
}
});
}
@Override
public void onTimer(Object key) {
if (key.equals("key")) {
open = false;
}
}
};
}
}
// #materialized
public class FirstValue<A>
extends GraphStageWithMaterializedValue<FlowShape<A, A>, CompletionStage<A>> {
public final Inlet<A> in = Inlet.create("FirstValue.in");
public final Outlet<A> out = Outlet.create("FirstValue.out");
private final FlowShape<A, A> shape = FlowShape.of(in, out);
@Override
public FlowShape<A, A> shape() {
return shape;
}
@Override
public Tuple2<GraphStageLogic, CompletionStage<A>> createLogicAndMaterializedValue(
Attributes inheritedAttributes) {
Promise<A> promise = Futures.promise();
GraphStageLogic logic =
new GraphStageLogic(shape) {
{
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
A elem = grab(in);
promise.success(elem);
push(out, elem);
// replace handler with one just forwarding
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
push(out, grab(in));
}
});
}
});
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
pull(in);
}
});
}
};
return new Tuple2(logic, promise.future());
}
}
// #async-side-channel
// will close upstream when the future completes
public class KillSwitch<A> extends GraphStage<FlowShape<A, A>> {
private final CompletionStage<Done> switchF;
public KillSwitch(CompletionStage<Done> switchF) {
this.switchF = switchF;
}
public final Inlet<A> in = Inlet.create("KillSwitch.in");
public final Outlet<A> out = Outlet.create("KillSwitch.out");
private final FlowShape<A, A> shape = FlowShape.of(in, out);
@Override
public FlowShape<A, A> shape() {
return shape;
}
@Override
public GraphStageLogic createLogic(Attributes inheritedAttributes) {
return new GraphStageLogic(shape) {
{
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
push(out, grab(in));
}
});
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
pull(in);
}
});
}
@Override
public void preStart() {
AsyncCallback<Done> callback =
createAsyncCallback(
new Procedure<Done>() {
@Override
public void apply(Done param) throws Exception {
completeStage();
}
});
ExecutionContext ec = system.dispatcher();
switchF.thenAccept(callback::invoke);
}
};
}
}
// #one-to-many
public class Duplicator<A> extends GraphStage<FlowShape<A, A>> {
public final Inlet<A> in = Inlet.create("Duplicator.in");
public final Outlet<A> out = Outlet.create("Duplicator.out");
private final FlowShape<A, A> shape = FlowShape.of(in, out);
@Override
public FlowShape<A, A> shape() {
return shape;
}
public GraphStageLogic createLogic(Attributes inheritedAttributes) {
return new GraphStageLogic(shape) {
// Again: note that all mutable state
// MUST be inside the GraphStageLogic
Option<A> lastElem = Option.none();
{
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
A elem = grab(in);
lastElem = Option.some(elem);
push(out, elem);
}
@Override
public void onUpstreamFinish() {
if (lastElem.isDefined()) {
emit(out, lastElem.get());
}
complete(out);
}
});
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
if (lastElem.isDefined()) {
push(out, lastElem.get());
lastElem = Option.none();
} else {
pull(in);
}
}
});
}
};
}
}
// #many-to-one
public final class Filter<A> extends GraphStage<FlowShape<A, A>> {
private final Predicate<A> p;
public Filter(Predicate<A> p) {
this.p = p;
}
public final Inlet<A> in = Inlet.create("Filter.in");
public final Outlet<A> out = Outlet.create("Filter.out");
private final FlowShape<A, A> shape = FlowShape.of(in, out);
@Override
public FlowShape<A, A> shape() {
return shape;
}
public GraphStageLogic createLogic(Attributes inheritedAttributes) {
return new GraphStageLogic(shape) {
{
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
A elem = grab(in);
if (p.test(elem)) {
push(out, elem);
} else {
pull(in);
}
}
});
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
pull(in);
}
});
}
};
}
}
// #one-to-one
public class Map<A, B> extends GraphStage<FlowShape<A, B>> {
private final Function<A, B> f;
public Map(Function<A, B> f) {
this.f = f;
}
public final Inlet<A> in = Inlet.create("Map.in");
public final Outlet<B> out = Outlet.create("Map.out");
private final FlowShape<A, B> shape = FlowShape.of(in, out);
@Override
public FlowShape<A, B> shape() {
return shape;
}
@Override
public GraphStageLogic createLogic(Attributes inheritedAttributes) {
return new GraphStageLogic(shape) {
{
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
try {
push(out, f.apply(grab(in)));
} catch (Exception ex) {
failStage(ex);
}
}
});
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
pull(in);
}
});
}
};
}
}
// #simpler-one-to-many
public class Duplicator2<A> extends GraphStage<FlowShape<A, A>> {
public final Inlet<A> in = Inlet.create("Duplicator.in");
public final Outlet<A> out = Outlet.create("Duplicator.out");
private final FlowShape<A, A> shape = FlowShape.of(in, out);
@Override
public FlowShape<A, A> shape() {
return shape;
}
@Override
public GraphStageLogic createLogic(Attributes inheritedAttributes) {
return new GraphStageLogic(shape) {
{
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
A elem = grab(in);
// this will temporarily suspend this handler until the two elems
// are emitted and then reinstates it
emitMultiple(out, Arrays.asList(elem, elem).iterator());
}
});
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
pull(in);
}
});
}
};
}
}
// #simple-source
public class NumbersSource extends GraphStage<SourceShape<Integer>> {
// Define the (sole) output port of this stage
public final Outlet<Integer> out = Outlet.create("NumbersSource.out");
// Define the shape of this stage, which is SourceShape with the port we defined above
private final SourceShape<Integer> shape = SourceShape.of(out);
@Override
public SourceShape<Integer> shape() {
return shape;
}
// This is where the actual (possibly stateful) logic is created
@Override
public GraphStageLogic createLogic(Attributes inheritedAttributes) {
return new GraphStageLogic(shape()) {
// All state MUST be inside the GraphStageLogic,
// never inside the enclosing GraphStage.
// This state is safe to access and modify from all the
// callbacks that are provided by GraphStageLogic and the
// registered handlers.
private int counter = 1;
{
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
push(out, counter);
counter += 1;
}
});
}
};
}
}
// #detached
public class TwoBuffer<A> extends GraphStage<FlowShape<A, A>> {
public final Inlet<A> in = Inlet.create("TwoBuffer.in");
public final Outlet<A> out = Outlet.create("TwoBuffer.out");
private final FlowShape<A, A> shape = FlowShape.of(in, out);
@Override
public FlowShape<A, A> shape() {
return shape;
}
@Override
public GraphStageLogic createLogic(Attributes inheritedAttributes) {
return new GraphStageLogic(shape) {
private final int SIZE = 2;
private Queue<A> buffer = new ArrayDeque<>(SIZE);
private boolean downstreamWaiting = false;
private boolean isBufferFull() {
return buffer.size() == SIZE;
}
@Override
public void preStart() {
// a detached stage needs to start upstream demand
// itself as it is not triggered by downstream demand
pull(in);
}
{
setHandler(
in,
new AbstractInHandler() {
@Override
public void onPush() {
A elem = grab(in);
buffer.add(elem);
if (downstreamWaiting) {
downstreamWaiting = false;
A bufferedElem = buffer.poll();
push(out, bufferedElem);
}
if (!isBufferFull()) {
pull(in);
}
}
@Override
public void onUpstreamFinish() {
if (!buffer.isEmpty()) {
// emit the rest if possible
emitMultiple(out, buffer.iterator());
}
completeStage();
}
});
setHandler(
out,
new AbstractOutHandler() {
@Override
public void onPull() {
if (buffer.isEmpty()) {
downstreamWaiting = true;
} else {
A elem = buffer.poll();
push(out, elem);
}
if (!isBufferFull() && !hasBeenPulled(in)) {
pull(in);
}
}
});
}
};
}
}