org.jboss.threads.BalancingExecutor Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
/*
* JBoss, Home of Professional Open Source.
* Copyright 2017 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* Licensed 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.jboss.threads;
import static java.util.concurrent.atomic.AtomicReferenceFieldUpdater.newUpdater;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ThreadLocalRandom;
import org.wildfly.common.Assert;
/**
* A simple load-balancing executor. If no delegate executors are defined, then tasks are rejected. Executors are
* chosen in a random fashion.
*/
public class BalancingExecutor implements Executor {
private static final Executor[] NO_EXECUTORS = new Executor[0];
private volatile Executor[] executors = NO_EXECUTORS;
private static final AtomicArray executorsUpdater = AtomicArray.create(newUpdater(BalancingExecutor.class, Executor[].class, "executors"), NO_EXECUTORS);
/**
* Construct a new instance.
*/
public BalancingExecutor() {
}
/**
* Construct a new instance.
*
* @param executors the initial list of executors to delegate to
*/
public BalancingExecutor(Executor... executors) {
if (executors != null && executors.length > 0) {
final Executor[] clone = executors.clone();
for (int i = 0; i < clone.length; i++) {
Assert.checkNotNullArrayParam("executors", i, clone[i]);
}
executorsUpdater.set(this, clone);
} else {
executorsUpdater.clear(this);
}
}
/**
* Execute a task.
*
* @param command the task to execute
* @throws RejectedExecutionException if no executors are available to run the task
*/
public void execute(final Runnable command) throws RejectedExecutionException {
final Executor[] executors = this.executors;
final int len = executors.length;
if (len == 0) {
throw Messages.msg.noExecutorsAvailable();
}
executors[ThreadLocalRandom.current().nextInt(len)].execute(command);
}
/**
* Clear out all delegate executors at once. Tasks will be rejected until another delegate executor is added.
*/
public void clear() {
executorsUpdater.clear(this);
}
/**
* Add a delegate executor.
*
* @param executor the executor to add
*/
public void addExecutor(final Executor executor) {
Assert.checkNotNullParam("executor", executor);
synchronized (this) {
executorsUpdater.add(this, executor);
}
}
/**
* Remove a delegate executor.
*
* @param executor the executor to remove
*/
public void removeExecutor(final Executor executor) {
if (executor == null) {
return;
}
synchronized (this) {
executorsUpdater.remove(this, executor, true);
}
}
}