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ActiveMQScheduledComponent.java
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ActiveMQScheduledComponent.java
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/**
* 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.activemq.artemis.core.server;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.activemq.artemis.utils.ActiveMQThreadFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.invoke.MethodHandles;
/**
* This is for components with a scheduled at a fixed rate.
*/
public abstract class ActiveMQScheduledComponent implements ActiveMQComponent, Runnable {
private static final Logger logger = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
protected ScheduledExecutorService scheduledExecutorService;
private boolean startedOwnScheduler;
/** initialDelay < 0 would mean no initial delay, use the period instead */
private long initialDelay;
private long period;
private TimeUnit timeUnit;
protected final Executor executor;
private volatile boolean isStarted;
private ScheduledFuture future;
private final boolean onDemand;
// The start/stop actions shouldn't interact concurrently with delay so it doesn't need to be volatile
private AtomicBoolean bookedForRunning;
/**
* It creates a scheduled component that can trigger {@link #run()} with a fixed {@code checkPeriod} on a configured {@code executor}.
*
* @param scheduledExecutorService the {@link ScheduledExecutorService} that periodically trigger {@link #run()} on the configured {@code executor}
* @param executor the {@link Executor} that execute {@link #run()} when triggered
* @param initialDelay the time to delay first execution
* @param checkPeriod the delay between the termination of one execution and the start of the next
* @param timeUnit the time unit of the {@code initialDelay} and {@code checkPeriod} parameters
* @param onDemand if {@code true} the task won't be scheduled on {@link #start()}, {@code false} otherwise
*/
public ActiveMQScheduledComponent(ScheduledExecutorService scheduledExecutorService,
Executor executor,
long initialDelay,
long checkPeriod,
TimeUnit timeUnit,
boolean onDemand) {
this.executor = executor;
this.scheduledExecutorService = scheduledExecutorService;
this.initialDelay = initialDelay;
this.period = checkPeriod;
this.timeUnit = timeUnit;
this.onDemand = onDemand;
this.bookedForRunning = new AtomicBoolean(false);
this.isStarted = false;
}
/**
* It creates a scheduled component that can trigger {@link #run()} with a fixed {@code checkPeriod} on a configured {@code executor}.
*
* @param scheduledExecutorService the {@link ScheduledExecutorService} that periodically trigger {@link #run()} on the configured {@code executor}
* @param initialDelay the time to delay first execution
* @param checkPeriod the delay between the termination of one execution and the start of the next
* @param timeUnit the time unit of the {@code initialDelay} and {@code checkPeriod} parameters
* @param onDemand if {@code true} the task won't be scheduled on {@link #start()}, {@code false} otherwise
*/
public ActiveMQScheduledComponent(ScheduledExecutorService scheduledExecutorService,
long initialDelay,
long checkPeriod,
TimeUnit timeUnit,
boolean onDemand) {
this(scheduledExecutorService, null, initialDelay, checkPeriod, timeUnit, onDemand);
}
/**
* It creates a scheduled component that can trigger {@link #run()} with a fixed {@code checkPeriod} on a configured {@code executor}.
*
* <p>
* The component created will have {@code initialDelay} defaulted to {@code checkPeriod}.
*
* @param scheduledExecutorService the {@link ScheduledExecutorService} that periodically trigger {@link #run()} on the configured {@code executor}
* @param executor the {@link Executor} that execute {@link #run()} when triggered
* @param checkPeriod the delay between the termination of one execution and the start of the next
* @param timeUnit the time unit of the {@code initialDelay} and {@code checkPeriod} parameters
* @param onDemand if {@code true} the task won't be scheduled on {@link #start()}, {@code false} otherwise
*/
public ActiveMQScheduledComponent(ScheduledExecutorService scheduledExecutorService,
Executor executor,
long checkPeriod,
TimeUnit timeUnit,
boolean onDemand) {
this(scheduledExecutorService, executor, -1, checkPeriod, timeUnit, onDemand);
}
/**
* It creates a scheduled component that can trigger {@link #run()} with a fixed {@code checkPeriod} on a configured {@code executor}.
*
* <p>
* This is useful for cases where we want our own scheduler executor: on {@link #start()} it will create a fresh new single-threaded {@link ScheduledExecutorService}
* using {@link #getThreadFactory()} and {@link #getThisClassLoader()}, while on {@link #stop()} it will garbage it.
*
* @param initialDelay the time to delay first execution
* @param checkPeriod the delay between the termination of one execution and the start of the next
* @param timeUnit the time unit of the {@code initialDelay} and {@code checkPeriod} parameters
* @param onDemand if {@code true} the task won't be scheduled on {@link #start()}, {@code false} otherwise
*/
public ActiveMQScheduledComponent(long initialDelay, long checkPeriod, TimeUnit timeUnit, boolean onDemand) {
this(null, null, initialDelay, checkPeriod, timeUnit, onDemand);
}
/**
* It creates a scheduled component that can trigger {@link #run()} with a fixed {@code checkPeriod} on a configured {@code executor}.
*
* <p>
* This is useful for cases where we want our own scheduler executor.
* The component created will have {@code initialDelay} defaulted to {@code checkPeriod}.
*
* @param checkPeriod the delay between the termination of one execution and the start of the next
* @param timeUnit the time unit of the {@code initialDelay} and {@code checkPeriod} parameters
* @param onDemand if {@code true} the task won't be scheduled on {@link #start()}, {@code false} otherwise
*/
public ActiveMQScheduledComponent(long checkPeriod, TimeUnit timeUnit, boolean onDemand) {
this(null, null, checkPeriod, checkPeriod, timeUnit, onDemand);
}
@Override
public synchronized void start() {
if (isStarted) {
// already started
return;
}
isStarted = true;
if (scheduledExecutorService == null) {
scheduledExecutorService = new ScheduledThreadPoolExecutor(1, getThreadFactory());
startedOwnScheduler = true;
}
if (onDemand) {
return;
}
if (period >= 0) {
final AtomicBoolean booked = this.bookedForRunning;
future = scheduledExecutorService.scheduleWithFixedDelay(() -> runForScheduler(booked), initialDelay >= 0 ? initialDelay : period, period, timeUnit);
} else {
logger.trace("did not start scheduled executor on {} because period was configured as {}", this, period);
}
}
protected ActiveMQThreadFactory getThreadFactory() {
return new ActiveMQThreadFactory(this.getClass().getSimpleName() + "-scheduled-threads", false, getThisClassLoader());
}
private ClassLoader getThisClassLoader() {
return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
@Override
public ClassLoader run() {
return ActiveMQScheduledComponent.this.getClass().getClassLoader();
}
});
}
/**
* A delay request can succeed only if:
* <ul>
* <li>there is no other pending delay request
* <li>there is no pending execution request
* </ul>
* <p>
* When a delay request succeed it schedule a new execution to happen in {@link #getPeriod()}.<br>
*/
public boolean delay() {
final AtomicBoolean booked = this.bookedForRunning;
if (!booked.compareAndSet(false, true)) {
return false;
}
try {
scheduledExecutorService.schedule(() -> bookedRunForScheduler(booked), period, timeUnit);
return true;
} catch (RejectedExecutionException e) {
booked.set(false);
throw e;
}
}
public long getPeriod() {
return period;
}
public synchronized ActiveMQScheduledComponent setPeriod(long period) {
this.period = period;
restartIfNeeded();
return this;
}
public synchronized ActiveMQScheduledComponent setPeriod(long period, TimeUnit unit) {
this.period = period;
this.timeUnit = unit;
restartIfNeeded();
return this;
}
public long getInitialDelay() {
return initialDelay;
}
public synchronized ActiveMQScheduledComponent setInitialDelay(long initialDelay) {
this.initialDelay = initialDelay;
restartIfNeeded();
return this;
}
/**
* Useful to change a running schedule and avoid multiple restarts.
*/
public synchronized ActiveMQScheduledComponent setInitialDelayAndPeriod(long initialDelay, long period) {
this.period = period;
this.initialDelay = initialDelay;
restartIfNeeded();
return this;
}
/**
* Useful to change a running schedule and avoid multiple restarts.
*/
public synchronized ActiveMQScheduledComponent setInitialDelayAndPeriod(long initialDelay,
long period,
TimeUnit timeUnit) {
this.period = period;
this.initialDelay = initialDelay;
this.timeUnit = timeUnit;
restartIfNeeded();
return this;
}
public TimeUnit getTimeUnit() {
return timeUnit;
}
public synchronized ActiveMQScheduledComponent setTimeUnit(TimeUnit timeUnit) {
this.timeUnit = timeUnit;
restartIfNeeded();
return this;
}
@Override
public synchronized void stop() {
if (!isStarted) {
return;
}
isStarted = false;
// Replace the existing one: a new periodic task or any new delay after stop
// won't interact with the previously running ones
this.bookedForRunning = new AtomicBoolean(false);
if (future != null) {
future.cancel(false);
future = null;
}
if (startedOwnScheduler) {
this.scheduledExecutorService.shutdownNow();
scheduledExecutorService = null;
startedOwnScheduler = false;
}
}
@Override
public boolean isStarted() {
return isStarted;
}
// this will restart the scheduled component upon changes
private void restartIfNeeded() {
if (isStarted()) {
stop();
start();
}
}
private void runForExecutor(AtomicBoolean booked) {
// It unblocks:
// - a new delay request
// - next periodic run request (in case of executor != null)
// Although tempting, don't move this one after ActiveMQScheduledComponent.this.run():
// - it can cause "delay" to change semantic ie a racing delay while finished executing the task, won't succeed
// - it won't prevent "slow tasks" to accumulate, because slowness cannot be measured inside running method;
// it just cause skipping runs for perfectly timed executions too
boolean alwaysTrue = booked.compareAndSet(true, false);
assert alwaysTrue;
ActiveMQScheduledComponent.this.run();
}
private void bookedRunForScheduler(AtomicBoolean booked) {
assert booked.get();
if (executor != null) {
try {
executor.execute(() -> runForExecutor(booked));
} catch (RejectedExecutionException e) {
if (booked != null) {
booked.set(false);
}
throw e;
}
} else {
runForExecutor(booked);
}
}
private void runForScheduler(AtomicBoolean booked) {
if (!booked.compareAndSet(false, true)) {
// let's skip this execution because there is:
// - a previously submitted period task yet to start -> executor is probably overbooked!
// - a pending delay request
return;
}
bookedRunForScheduler(booked);
}
}