/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you 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 org.apache.giraph.zk;

 import java.util.concurrent.TimeUnit;

 import java.util.concurrent.locks.Condition;

 import java.util.concurrent.locks.Lock;

 import java.util.concurrent.locks.ReentrantLock;

 import org.apache.giraph.time.SystemTime;

 import org.apache.giraph.time.Time;

 import org.apache.hadoop.util.Progressable;

 import org.apache.log4j.Logger;

 /**

  * A lock with a predicate that was be used to synchronize events and keep the

  * job context updated while waiting.

  */

 public class PredicateLock implements BspEvent {

   /** Class logger */

   private static final Logger LOG = Logger.getLogger(PredicateLock.class);

   /** Default msecs to refresh the progress meter */

   private static final int DEFAULT_MSEC_PERIOD = 10000;

   /** Progressable for reporting progress (Job context) */

   protected final Progressable progressable;

   /** Actual mses to refresh the progress meter */

   private final int msecPeriod;

   /** Lock */

   private Lock lock = new ReentrantLock();

   /** Condition associated with lock */

   private Condition cond = lock.newCondition();

   /** Predicate */

   private boolean eventOccurred = false;

   /** Keeps track of the time */

   private final Time time;

   /**

    * Constructor with default values.

    *

    * @param progressable used to report progress() (usually a Mapper.Context)

    */

   public PredicateLock(Progressable progressable) {

     this(progressable, DEFAULT_MSEC_PERIOD, SystemTime.get());

   }

   /**

    * Constructor.

    *

    * @param progressable used to report progress() (usually a Mapper.Context)

    * @param msecPeriod Msecs between progress reports

    * @param time Time implementation

    */

   public PredicateLock(Progressable progressable, int msecPeriod, Time time) {

     this.progressable = progressable;

     this.msecPeriod = msecPeriod;

     this.time = time;

   }

   @Override

   public void reset() {

     lock.lock();

     try {

       eventOccurred = false;

     } finally {

       lock.unlock();

     }

   }

   @Override

   public void signal() {

     lock.lock();

     try {

       eventOccurred = true;

       cond.signalAll();

     } finally {

       lock.unlock();

     }

   }

   @Override

   public boolean waitMsecs(int msecs) {

     if (msecs < 0) {

       throw new RuntimeException("waitMsecs: msecs cannot be negative!");

     }

     long maxMsecs = time.getMilliseconds() + msecs;

     int curMsecTimeout = 0;

     lock.lock();

     try {

       while (!eventOccurred) {

         curMsecTimeout =

             Math.min(msecs, msecPeriod);

         if (LOG.isDebugEnabled()) {

           LOG.debug("waitMsecs: Wait for " + curMsecTimeout);

         }

         try {

           boolean signaled =

               cond.await(curMsecTimeout, TimeUnit.MILLISECONDS);

           if (LOG.isDebugEnabled()) {

             LOG.debug("waitMsecs: Got timed signaled of " +

               signaled);

           }

         } catch (InterruptedException e) {

           throw new IllegalStateException(

             "waitMsecs: Caught interrupted " +

             "exception on cond.await() " +

             curMsecTimeout, e);

         }

         if (time.getMilliseconds() > maxMsecs) {

           return false;

         }

         msecs = Math.max(0, msecs - curMsecTimeout);

         progressable.progress(); // go around again

       }

     } finally {

       lock.unlock();

     }

     return true;

   }

   @Override

   public void waitForTimeoutOrFail(long timeout) {

     long t0 = System.currentTimeMillis();

     while (!waitMsecs(msecPeriod)) {

       if (System.currentTimeMillis() > t0 + timeout) {

         throw new RuntimeException("Timeout waiting");

       }

       progressable.progress();

     }

   }

 }