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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.service.executor;
import java.util.logging.Level;
import java.time.Duration;
import java.util.Optional;
import java.util.logging.Logger;
/**
* Provides the {@link Cancellable} returned by {@link RunletExecutorImpl#scheduleWithFixedDelay(Runlet, Duration)},
* and ensuring the correct semantic execution of the {@link Runlet}.
*
* @author hakonhall
*/
class CancellableImpl implements Cancellable, Runnable {
private static final Logger logger = Logger.getLogger(CancellableImpl.class.getName());
private final Object monitor = new Object();
private Runlet runlet;
private Optional<Runnable> periodicExecutionCancellation = Optional.empty();
private boolean running = false;
private boolean cancelled = false;
public CancellableImpl(Runlet runlet) {
this.runlet = runlet;
}
/**
* Provide a way for {@code this} to cancel the periodic execution of {@link #run()}.
*
* <p>Must be called happens-before {@link #cancel()}.
*/
void setPeriodicExecutionCancellationCallback(Runnable periodicExecutionCancellation) {
synchronized (monitor) {
if (cancelled) {
throw new IllegalStateException("Cancellation callback set after cancel()");
}
this.periodicExecutionCancellation = Optional.of(periodicExecutionCancellation);
}
}
/**
* Cancel the execution of the {@link Runlet}.
*
* <ul>
* <li>Either the runlet will not execute any more {@link Runlet#run()}s, and {@link Runlet#close()}
* and then {@code periodicExecutionCancellation} will be called synchronously, or
* <li>{@link #run()} is executing concurrently by another thread {@code T}. The last call to
* {@link Runlet#run()} will be called by {@code T} shortly, is in progress, or has completed.
* Then {@code T} will call {@link Runlet#close()} followed by {@code periodicExecutionCancellation},
* before the return of {@link #run()}.
* </ul>
*
* <p>{@link #setPeriodicExecutionCancellationCallback(Runnable)} must be called happens-before this method.
*/
@Override
public void cancel() {
synchronized (monitor) {
if (!periodicExecutionCancellation.isPresent()) {
throw new IllegalStateException("setPeriodicExecutionCancellationCallback has not been called before cancel");
}
cancelled = true;
if (running) return;
}
runlet.close();
periodicExecutionCancellation.get().run();
}
/**
* Must be called periodically in happens-before order, but may be called concurrently with
* {@link #setPeriodicExecutionCancellationCallback(Runnable)} and {@link #cancel()}.
*/
@Override
public void run() {
try {
synchronized (monitor) {
if (cancelled) return;
running = true;
}
runlet.run();
synchronized (monitor) {
running = false;
if (!cancelled) return;
if (!periodicExecutionCancellation.isPresent()) {
// This should be impossible given the implementation of cancel()
throw new IllegalStateException("Cancelled before cancellation callback was set");
}
}
runlet.close();
periodicExecutionCancellation.get().run();
} catch (Throwable e) {
logger.log(Level.SEVERE, "Failed run of periodic execution", e);
}
}
}
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