content: // Copyright 2014 The Bazel Authors. All rights reserved.
  //
  // 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.android.apps.common.testing.broker.shell;
  
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  /**
   * <p>{@link KillableObserver} implementation which will kill its observed
   * {@link Killable} if it is still being observed after a given amount
   * of time has elapsed.</p>
   *
   * <p>Note that this class can only observe one {@link Killable} at a time;
   * multiple instances should be used for concurrent calls to
   * {@link Command#execute(byte[], KillableObserver, boolean)}.</p>
   */
  public final class TimeoutKillableObserver implements KillableObserver {
  
    private static final Logger log =
        Logger.getLogger(TimeoutKillableObserver.class.getCanonicalName());
  
    private final long timeoutMS;
    private Killable killable;
    private SleeperThread sleeperThread;
    private boolean timedOut;
  
    // TODO(bazel-team): I'd like to use ThreadPool2, but it doesn't currently
    // provide a way to interrupt a thread
  
    public TimeoutKillableObserver(final long timeoutMS) {
      this.timeoutMS = timeoutMS;
    }
  
    /**
     * Starts a new {@link Thread} to wait for the timeout period. This is
     * interrupted by the {@link #stopObserving(Killable)} method.
     *
     * @param killable killable to kill when the timeout period expires
     */
    @Override
    public synchronized void startObserving(final Killable killable) {
      this.timedOut = false;
      this.killable = killable;
      this.sleeperThread = new SleeperThread();
      this.sleeperThread.start();
    }
  
    @Override
    public synchronized void stopObserving(final Killable killable) {
      if (!this.killable.equals(killable)) {
        throw new IllegalStateException("start/stopObservering called with " +
                                        "different Killables");
      }
      if (sleeperThread.isAlive()) {
        sleeperThread.interrupt();
      }
      this.killable = null;
      sleeperThread = null;
    }
  
    private final class SleeperThread extends Thread {
      @Override public void run() {
        try {
          if (log.isLoggable(Level.FINE)) {
            log.fine("Waiting for " + timeoutMS + "ms to kill process");
          }
          Thread.sleep(timeoutMS);
          // timeout expired; kill it
          synchronized (TimeoutKillableObserver.this) {
            if (killable != null) {
              log.fine("Killing process");
              killable.kill();
              timedOut = true;
            }
          }
        } catch (InterruptedException ie) {
          // continue -- process finished before timeout
          log.fine("Wait interrupted since process finished; continuing...");
        }
      }
    }
  
    /**
     * Returns true if the observed process was killed by this observer.
     */
    public synchronized boolean hasTimedOut() {
      // synchronized needed for memory model visibility.
      return timedOut;
    }
  }
  