001/*
002 * Copyright (C) 2009 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.util.concurrent;
016
017import static com.google.common.util.concurrent.Platform.restoreInterruptIfIsInterruptedException;
018
019import com.google.common.annotations.GwtIncompatible;
020import com.google.common.base.Supplier;
021import com.google.errorprone.annotations.CanIgnoreReturnValue;
022import com.google.j2objc.annotations.WeakOuter;
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" but may need one during startup
029 * and shutdown. Subclasses can implement {@link #startUp} and {@link #shutDown} methods, each which
030 * run in an executor which by default uses a separate thread for each method.
031 *
032 * @author Chris Nokleberg
033 * @since 1.0
034 */
035@GwtIncompatible
036@ElementTypesAreNonnullByDefault
037public abstract class AbstractIdleService implements Service {
038
039  /* Thread names will look like {@code "MyService STARTING"}. */
040  private final Supplier<String> threadNameSupplier = new ThreadNameSupplier();
041
042  @WeakOuter
043  private final class ThreadNameSupplier implements Supplier<String> {
044    @Override
045    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
056    protected final void doStart() {
057      MoreExecutors.renamingDecorator(executor(), threadNameSupplier)
058          .execute(
059              new Runnable() {
060                @Override
061                public void run() {
062                  try {
063                    startUp();
064                    notifyStarted();
065                  } catch (Throwable t) {
066                    restoreInterruptIfIsInterruptedException(t);
067                    notifyFailed(t);
068                  }
069                }
070              });
071    }
072
073    @Override
074    protected final void doStop() {
075      MoreExecutors.renamingDecorator(executor(), threadNameSupplier)
076          .execute(
077              new Runnable() {
078                @Override
079                public void run() {
080                  try {
081                    shutDown();
082                    notifyStopped();
083                  } catch (Throwable t) {
084                    restoreInterruptIfIsInterruptedException(t);
085                    notifyFailed(t);
086                  }
087                }
088              });
089    }
090
091    @Override
092    public String toString() {
093      return AbstractIdleService.this.toString();
094    }
095  }
096
097  /** Constructor for use by subclasses. */
098  protected AbstractIdleService() {}
099
100  /** Start the service. */
101  protected abstract void startUp() throws Exception;
102
103  /** Stop the service. */
104  protected abstract void shutDown() throws Exception;
105
106  /**
107   * Returns the {@link Executor} that will be used to run this service. Subclasses may override
108   * this method to use a custom {@link Executor}, which may configure its worker thread with a
109   * specific name, thread group or priority. The returned executor's {@link
110   * Executor#execute(Runnable) execute()} method is called when this service is started and
111   * stopped, and should return promptly.
112   */
113  protected Executor executor() {
114    return new Executor() {
115      @Override
116      public void execute(Runnable command) {
117        MoreExecutors.newThread(threadNameSupplier.get(), command).start();
118      }
119    };
120  }
121
122  @Override
123  public String toString() {
124    return serviceName() + " [" + state() + "]";
125  }
126
127  @Override
128  public final boolean isRunning() {
129    return delegate.isRunning();
130  }
131
132  @Override
133  public final State state() {
134    return delegate.state();
135  }
136
137  /** @since 13.0 */
138  @Override
139  public final void addListener(Listener listener, Executor executor) {
140    delegate.addListener(listener, executor);
141  }
142
143  /** @since 14.0 */
144  @Override
145  public final Throwable failureCause() {
146    return delegate.failureCause();
147  }
148
149  /** @since 15.0 */
150  @CanIgnoreReturnValue
151  @Override
152  public final Service startAsync() {
153    delegate.startAsync();
154    return this;
155  }
156
157  /** @since 15.0 */
158  @CanIgnoreReturnValue
159  @Override
160  public final Service stopAsync() {
161    delegate.stopAsync();
162    return this;
163  }
164
165  /** @since 15.0 */
166  @Override
167  public final void awaitRunning() {
168    delegate.awaitRunning();
169  }
170
171  /** @since 15.0 */
172  @Override
173  public final void awaitRunning(long timeout, TimeUnit unit) throws TimeoutException {
174    delegate.awaitRunning(timeout, unit);
175  }
176
177  /** @since 15.0 */
178  @Override
179  public final void awaitTerminated() {
180    delegate.awaitTerminated();
181  }
182
183  /** @since 15.0 */
184  @Override
185  public final void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException {
186    delegate.awaitTerminated(timeout, unit);
187  }
188
189  /**
190   * Returns the name of this service. {@link AbstractIdleService} may include the name in debugging
191   * output.
192   *
193   * @since 14.0
194   */
195  protected String serviceName() {
196    return getClass().getSimpleName();
197  }
198}