org.jboss.threads.Dependency 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).
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/*
* 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 java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;
import org.wildfly.common.Assert;
/**
* A task which depends on other tasks, and which may have tasks depending upon it. Such a task is automatically
* run when using a provided executor when all its dependencies are satisfied.
*/
public final class Dependency {
private static final AtomicIntegerFieldUpdater depUpdater = AtomicIntegerFieldUpdater.newUpdater(Dependency.class, "remainingDependencies");
/**
* Number of dependencies left before this task can start.
*/
@SuppressWarnings({ "UnusedDeclaration" })
private volatile int remainingDependencies;
private final Executor executor;
private final Object lock = new Object();
private Runner runner;
private State state;
Dependency(final Executor executor, final Runnable runnable, final int initialDepCount) {
this.executor = executor;
synchronized (lock) {
runner = new Runner(runnable);
state = State.WAITING;
remainingDependencies = initialDepCount;
}
}
void addDependent(Dependency task) {
synchronized (lock) {
switch (state) {
case WAITING:
case RUNNING: runner.dependents.add(task); return;
case FAILED: return;
case DONE: break; // fall out of lock
default: throw Assert.impossibleSwitchCase(state);
}
}
task.dependencyFinished();
}
void dependencyFinished() {
final AtomicIntegerFieldUpdater updater = depUpdater;
final int res = updater.decrementAndGet(this);
if (res == 0) {
final Dependency.Runner runner = this.runner;
synchronized (lock) {
try {
executor.execute(runner);
state = State.RUNNING;
} catch (RejectedExecutionException e) {
Messages.msg.taskSubmitFailed(e, runner.runnable);
state = State.FAILED;
// clear stuff out since this object will likely be kept alive longer than these objects need to be
runner.runnable = null;
runner.dependents = null;
this.runner = null;
}
}
} else if (res < 0) {
// oops?
updater.incrementAndGet(this);
}
}
private void dependencyFailed() {
final AtomicIntegerFieldUpdater updater = depUpdater;
final int res = updater.decrementAndGet(this);
synchronized (lock) {
state = State.FAILED;
final Dependency.Runner runner = this.runner;
// clear stuff out since this object will likely be kept alive longer than these objects need to be
runner.runnable = null;
runner.dependents = null;
this.runner = null;
}
if (res < 0) {
// oops?
updater.incrementAndGet(this);
}
}
private class Runner implements Runnable {
private List dependents = new ArrayList();
private Runnable runnable;
public Runner(final Runnable runnable) {
this.runnable = runnable;
}
public void run() {
boolean ok = false;
CTH.set(Dependency.this);
try {
runnable.run();
ok = true;
} finally {
CTH.set(null);
final List tasks;
synchronized (lock) {
tasks = dependents;
// clear stuff out in case some stupid executor holds on to the runnable
dependents = null;
runnable = null;
runner = null;
state = ok ? State.DONE : State.FAILED;
}
if (ok) {
for (Dependency task : tasks) {
task.dependencyFinished();
}
} else {
for (Dependency task : tasks) {
task.dependencyFailed();
}
}
}
}
}
private enum State {
/**
* Waiting for dependencies to be resolved.
*/
WAITING,
/**
* Now running.
*/
RUNNING,
/**
* Execution failed.
*/
FAILED,
/**
* Execution completed.
*/
DONE,
}
/**
* Get the dependency task which this thread is currently running. This may be used to add dependencies on the currently
* running task.
*
* @return the currently running task, or {@code null} if the current thread is not running a dependency task
*/
public static Dependency currentTask() {
return CTH.get();
}
private static final ThreadLocal CTH = new ThreadLocal();
}