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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.common.util.concurrent;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.common.component.Lifecycle;
import java.util.Objects;
/**
* {@code AbstractLifecycleRunnable} is a service-lifecycle aware {@link AbstractRunnable}.
*
* This simplifies the running and rescheduling of {@link Lifecycle}-based {@code Runnable}s.
*/
public abstract class AbstractLifecycleRunnable extends AbstractRunnable {
/**
* The monitored lifecycle for the associated service.
*/
private final Lifecycle lifecycle;
/**
* The service's logger (note: this is passed in!).
*/
private final Logger logger;
/**
* {@link AbstractLifecycleRunnable} must be aware of the actual {@code lifecycle} to react properly.
*
* @param lifecycle The lifecycle to react too
* @param logger The logger to use when logging
* @throws NullPointerException if any parameter is {@code null}
*/
public AbstractLifecycleRunnable(Lifecycle lifecycle, Logger logger) {
this.lifecycle = Objects.requireNonNull(lifecycle, "lifecycle must not be null");
this.logger = Objects.requireNonNull(logger, "logger must not be null");
}
/**
* {@inheritDoc}
*
* This invokes {@link #doRunInLifecycle()} only if the {@link #lifecycle} is not stopped or closed. Otherwise it exits
* immediately.
*/
@Override
protected final void doRun() throws Exception {
// prevent execution if the service is stopped
if (lifecycle.stoppedOrClosed()) {
logger.trace("lifecycle is stopping. exiting");
return;
}
doRunInLifecycle();
}
/**
* Perform runnable logic, but only if the {@link #lifecycle} is not stopped or closed.
*
* @throws InterruptedException if the run method throws an {@link InterruptedException}
*/
protected abstract void doRunInLifecycle() throws Exception;
/**
* {@inheritDoc}
*
* This overrides the default behavior of {@code onAfter} to add the caveat that it only runs if the {@link #lifecycle} is not
* stopped or closed.
*
* Note: this does not guarantee that it won't be stopped concurrently as it invokes {@link #onAfterInLifecycle()},
* but it's a solid attempt at preventing it. For those that use this for rescheduling purposes, the next invocation would be
* effectively cancelled immediately if that's the case.
*
* @see #onAfterInLifecycle()
*/
@Override
public final void onAfter() {
if (lifecycle.stoppedOrClosed() == false) {
onAfterInLifecycle();
}
}
/**
* This method is invoked in the finally block of the run method, but it is only executed if the {@link #lifecycle} is not
* stopped or closed.
*
* This method is most useful for rescheduling the next iteration of the current runnable.
*/
protected void onAfterInLifecycle() {
// nothing by default
}
}