001/*
002 * Copyright (C) 2009 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.util.concurrent;
018
019import com.google.common.annotations.Beta;
020import com.google.common.base.Supplier;
021import com.google.j2objc.annotations.WeakOuter;
022
023import java.util.concurrent.Executor;
024import java.util.concurrent.TimeUnit;
025import java.util.concurrent.TimeoutException;
026
027/**
028 * Base class for services that do not need a thread while "running"
029 * but may need one during startup and shutdown. Subclasses can
030 * implement {@link #startUp} and {@link #shutDown} methods, each
031 * which run in a executor which by default uses a separate thread
032 * for each method.
033 *
034 * @author Chris Nokleberg
035 * @since 1.0
036 */
037@Beta
038public abstract class AbstractIdleService implements Service {
039
040  /* Thread names will look like {@code "MyService STARTING"}. */
041  private final Supplier<String> threadNameSupplier = new ThreadNameSupplier();
042
043  @WeakOuter
044  private final class ThreadNameSupplier implements Supplier<String> {
045    @Override public String get() {
046      return serviceName() + " " + state();
047    }
048  }
049
050  /* use AbstractService for state management */
051  private final Service delegate = new DelegateService();
052
053  @WeakOuter
054  private final class DelegateService extends AbstractService {
055    @Override protected final void doStart() {
056      MoreExecutors.renamingDecorator(executor(), threadNameSupplier)
057          .execute(new Runnable() {
058            @Override public void run() {
059              try {
060                startUp();
061                notifyStarted();
062              } catch (Throwable t) {
063                notifyFailed(t);
064              }
065            }
066          });
067    }
068
069    @Override protected final void doStop() {
070      MoreExecutors.renamingDecorator(executor(), threadNameSupplier)
071          .execute(new Runnable() {
072            @Override public void run() {
073              try {
074                shutDown();
075                notifyStopped();
076              } catch (Throwable t) {
077                notifyFailed(t);
078              }
079            }
080          });
081    }
082
083    @Override public String toString() {
084      return AbstractIdleService.this.toString();
085    }
086  }
087
088  /** Constructor for use by subclasses. */
089  protected AbstractIdleService() {}
090
091  /** Start the service. */
092  protected abstract void startUp() throws Exception;
093
094  /** Stop the service. */
095  protected abstract void shutDown() throws Exception;
096
097  /**
098   * Returns the {@link Executor} that will be used to run this service.
099   * Subclasses may override this method to use a custom {@link Executor}, which
100   * may configure its worker thread with a specific name, thread group or
101   * priority. The returned executor's {@link Executor#execute(Runnable)
102   * execute()} method is called when this service is started and stopped,
103   * and should return promptly.
104   */
105  protected Executor executor() {
106    return new Executor() {
107      @Override public void execute(Runnable command) {
108        MoreExecutors.newThread(threadNameSupplier.get(), command).start();
109      }
110    };
111  }
112
113  @Override public String toString() {
114    return serviceName() + " [" + state() + "]";
115  }
116
117  @Override public final boolean isRunning() {
118    return delegate.isRunning();
119  }
120
121  @Override public final State state() {
122    return delegate.state();
123  }
124
125  /**
126   * @since 13.0
127   */
128  @Override public final void addListener(Listener listener, Executor executor) {
129    delegate.addListener(listener, executor);
130  }
131  
132  /**
133   * @since 14.0
134   */
135  @Override public final Throwable failureCause() {
136    return delegate.failureCause();
137  }
138  
139  /**
140   * @since 15.0
141   */
142  @Override public final Service startAsync() {
143    delegate.startAsync();
144    return this;
145  }
146  
147  /**
148   * @since 15.0
149   */
150  @Override public final Service stopAsync() {
151    delegate.stopAsync();
152    return this;
153  }
154  
155  /**
156   * @since 15.0
157   */
158  @Override public final void awaitRunning() {
159    delegate.awaitRunning();
160  }
161  
162  /**
163   * @since 15.0
164   */
165  @Override public final void awaitRunning(long timeout, TimeUnit unit) throws TimeoutException {
166    delegate.awaitRunning(timeout, unit);
167  }
168  
169  /**
170   * @since 15.0
171   */
172  @Override public final void awaitTerminated() {
173    delegate.awaitTerminated();
174  }
175  
176  /**
177   * @since 15.0
178   */
179  @Override public final void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException {
180    delegate.awaitTerminated(timeout, unit);
181  }
182  
183  /**
184   * Returns the name of this service. {@link AbstractIdleService} may include the name in debugging
185   * output.
186   *
187   * @since 14.0
188   */
189  protected String serviceName() {
190    return getClass().getSimpleName();
191  }
192}