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/*
 * 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 shaded.shaded.com.google.common.util.concurrent;

import shaded.shaded.com.google.common.annotations.Beta;
import shaded.shaded.com.google.common.annotations.GwtIncompatible;
import shaded.shaded.com.google.common.base.Supplier;
import shaded.shaded.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() {
                    @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.
   *
   * 

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: * *

   *   public void run() {
   *     while ({@link #isRunning()}) {
   *       // perform a unit of work
   *     }
   *   }
   * 
* *

...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. * *

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. * *

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. * *

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. * *

Subclasses may override this method. * * @since 14.0 (present in 10.0 as getServiceName) */ protected String serviceName() { return getClass().getSimpleName(); } }





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