/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.beam.runners.core.triggers;
import java.util.Arrays;
/**
* Repeat a trigger, either until some condition is met or forever.
*
* <p>For example, to fire after the end of the window, and every time late data arrives:
* <pre> {@code
* Repeatedly.forever(AfterWatermark.isPastEndOfWindow());
* } </pre>
*
* <p>{@code Repeatedly.forever(someTrigger)} behaves like an infinite
* {@code AfterEach.inOrder(someTrigger, someTrigger, someTrigger, ...)}.
*/
public class RepeatedlyStateMachine extends TriggerStateMachine {
private static final int REPEATED = 0;
/**
* Create a composite trigger that repeatedly executes the trigger {@code repeated}, firing each
* time it fires and ignoring any indications to finish.
*
* <p>Unless used with {@link TriggerStateMachine#orFinally} the composite trigger will never
* finish.
*
* @param repeated the trigger to execute repeatedly.
*/
public static RepeatedlyStateMachine forever(TriggerStateMachine repeated) {
return new RepeatedlyStateMachine(repeated);
}
private RepeatedlyStateMachine(TriggerStateMachine repeated) {
super(Arrays.asList(repeated));
}
@Override
public void onElement(OnElementContext c) throws Exception {
getRepeated(c).invokeOnElement(c);
}
@Override
public void onMerge(OnMergeContext c) throws Exception {
getRepeated(c).invokeOnMerge(c);
}
@Override
public boolean shouldFire(TriggerStateMachine.TriggerContext context) throws Exception {
return getRepeated(context).invokeShouldFire(context);
}
@Override
public void onFire(TriggerContext context) throws Exception {
getRepeated(context).invokeOnFire(context);
if (context.trigger().isFinished(REPEATED)) {
// Reset tree will recursively clear the finished bits, and invoke clear.
context.forTrigger(getRepeated(context)).trigger().resetTree();
}
}
@Override
public String toString() {
return String.format("Repeatedly.forever(%s)", subTriggers.get(REPEATED));
}
private ExecutableTriggerStateMachine getRepeated(TriggerContext context) {
return context.trigger().subTrigger(REPEATED);
}
}