/*
* Copyright (C) 2009 The Guava Authors
*
* 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 com.google.common.util.concurrent;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Supplier;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Base class for services that can implement {@link #startUp}, {@link #run} and {@link #shutDown}
* methods. This class uses a single thread to execute the service; consider {@link AbstractService}
* if you would like to manage any threading manually.
*
* @author Jesse Wilson
* @since 1.0
*/
@Beta
@GwtIncompatible
public abstract class AbstractExecutionThreadService implements Service {
private static final Logger logger =
Logger.getLogger(AbstractExecutionThreadService.class.getName());
/* use AbstractService for state management */
private final Service delegate =
new AbstractService() {
@Override
protected final void doStart() {
Executor executor =
MoreExecutors.renamingDecorator(
executor(),
new Supplier<String>() {
@Override
public String get() {
return serviceName();
}
});
executor.execute(
new Runnable() {
@Override
public void run() {
try {
startUp();
notifyStarted();
// If stopAsync() is called while starting we may be in the STOPPING state in
// which case we should skip right down to shutdown.
if (isRunning()) {
try {
AbstractExecutionThreadService.this.run();
} catch (Throwable t) {
try {
shutDown();
} catch (Exception ignored) {
// TODO(lukes): if guava ever moves to java7, this would be a good
// candidate for a suppressed exception, or maybe we could generalize
// Closer.Suppressor
logger.log(
Level.WARNING,
"Error while attempting to shut down the service after failure.",
ignored);
}
notifyFailed(t);
return;
}
}
shutDown();
notifyStopped();
} catch (Throwable t) {
notifyFailed(t);
}
}
});
}
@Override
protected void doStop() {
triggerShutdown();
}
@Override
public String toString() {
return AbstractExecutionThreadService.this.toString();
}
};
/**
* Constructor for use by subclasses.
*/
protected AbstractExecutionThreadService() {}
/**
* Start the service. This method is invoked on the execution thread.
*
* <p>By default this method does nothing.
*/
protected void startUp() throws Exception {}
/**
* Run the service. This method is invoked on the execution thread. Implementations must respond
* to stop requests. You could poll for lifecycle changes in a work loop:
*
* <pre>
* public void run() {
* while ({@link #isRunning()}) {
* // perform a unit of work
* }
* }
* </pre>
*
* <p>...or you could respond to stop requests by implementing {@link #triggerShutdown()}, which
* should cause {@link #run()} to return.
*/
protected abstract void run() throws Exception;
/**
* Stop the service. This method is invoked on the execution thread.
*
* <p>By default this method does nothing.
*/
// TODO: consider supporting a TearDownTestCase-like API
protected void shutDown() throws Exception {}
/**
* Invoked to request the service to stop.
*
* <p>By default this method does nothing.
*/
protected void triggerShutdown() {}
/**
* Returns the {@link Executor} that will be used to run this service. Subclasses may override
* this method to use a custom {@link Executor}, which may configure its worker thread with a
* specific name, thread group or priority. The returned executor's {@link
* Executor#execute(Runnable) execute()} method is called when this service is started, and should
* return promptly.
*
* <p>The default implementation returns a new {@link Executor} that sets the name of its threads
* to the string returned by {@link #serviceName}
*/
protected Executor executor() {
return new Executor() {
@Override
public void execute(Runnable command) {
MoreExecutors.newThread(serviceName(), command).start();
}
};
}
@Override
public String toString() {
return serviceName() + " [" + state() + "]";
}
@Override
public final boolean isRunning() {
return delegate.isRunning();
}
@Override
public final State state() {
return delegate.state();
}
/**
* @since 13.0
*/
@Override
public final void addListener(Listener listener, Executor executor) {
delegate.addListener(listener, executor);
}
/**
* @since 14.0
*/
@Override
public final Throwable failureCause() {
return delegate.failureCause();
}
/**
* @since 15.0
*/
@CanIgnoreReturnValue
@Override
public final Service startAsync() {
delegate.startAsync();
return this;
}
/**
* @since 15.0
*/
@CanIgnoreReturnValue
@Override
public final Service stopAsync() {
delegate.stopAsync();
return this;
}
/**
* @since 15.0
*/
@Override
public final void awaitRunning() {
delegate.awaitRunning();
}
/**
* @since 15.0
*/
@Override
public final void awaitRunning(long timeout, TimeUnit unit) throws TimeoutException {
delegate.awaitRunning(timeout, unit);
}
/**
* @since 15.0
*/
@Override
public final void awaitTerminated() {
delegate.awaitTerminated();
}
/**
* @since 15.0
*/
@Override
public final void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException {
delegate.awaitTerminated(timeout, unit);
}
/**
* Returns the name of this service. {@link AbstractExecutionThreadService} may include the name
* in debugging output.
*
* <p>Subclasses may override this method.
*
* @since 14.0 (present in 10.0 as getServiceName)
*/
protected String serviceName() {
return getClass().getSimpleName();
}
}