hbase-common/src/main/java/org/apache/hadoop/hbase/ScheduledChore.java - hbase - Git at Google

 /**
  *
  * 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.hadoop.hbase;

 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 /**
  * ScheduledChore is a task performed on a period in hbase. ScheduledChores become active once
  * scheduled with a {@link ChoreService} via {@link ChoreService#scheduleChore(ScheduledChore)}. The
  * chore is run in a {@link ScheduledThreadPoolExecutor} and competes with other ScheduledChores for
  * access to the threads in the core thread pool. If an unhandled exception occurs, the chore
  * cancellation is logged. Implementers should consider whether or not the Chore will be able to
  * execute within the defined period. It is bad practice to define a ScheduledChore whose execution
  * time exceeds its period since it will try to hog one of the threads in the {@link ChoreService}'s
  * thread pool.
  * <p>
  * Don't subclass ScheduledChore if the task relies on being woken up for something to do, such as
  * an entry being added to a queue, etc.
  */
 @InterfaceAudience.Public
 public abstract class ScheduledChore implements Runnable {
   private static final Logger LOG = LoggerFactory.getLogger(ScheduledChore.class);

   private final String name;

   /**
    * Default values for scheduling parameters should they be excluded during construction
    */
   private final static TimeUnit DEFAULT_TIME_UNIT = TimeUnit.MILLISECONDS;
   private final static long DEFAULT_INITIAL_DELAY = 0;

   /**
    * Scheduling parameters. Used by ChoreService when scheduling the chore to run periodically
    */
   private final int period; // in TimeUnit units
   private final TimeUnit timeUnit;
   private final long initialDelay; // in TimeUnit units

   /**
    * Interface to the ChoreService that this ScheduledChore is scheduled with. null if the chore is
    * not scheduled.
    */
   private ChoreServicer choreServicer;

   /**
    * Variables that encapsulate the meaningful state information
    */
   private long timeOfLastRun = -1; // system time millis
   private long timeOfThisRun = -1; // system time millis
   private boolean initialChoreComplete = false;

   /**
    * A means by which a ScheduledChore can be stopped. Once a chore recognizes that it has been
    * stopped, it will cancel itself. This is particularly useful in the case where a single stopper
    * instance is given to multiple chores. In such a case, a single {@link Stoppable#stop(String)}
    * command can cause many chores to stop together.
    */
   private final Stoppable stopper;

   interface ChoreServicer {
     /**
      * Cancel any ongoing schedules that this chore has with the implementer of this interface.
      */
     public void cancelChore(ScheduledChore chore);
     public void cancelChore(ScheduledChore chore, boolean mayInterruptIfRunning);

     /**
      * @return true when the chore is scheduled with the implementer of this interface
      */
     public boolean isChoreScheduled(ScheduledChore chore);

     /**
      * This method tries to execute the chore immediately. If the chore is executing at the time of
      * this call, the chore will begin another execution as soon as the current execution finishes
      * <p>
      * If the chore is not scheduled with a ChoreService, this call will fail.
      * @return false when the chore could not be triggered immediately
      */
     public boolean triggerNow(ScheduledChore chore);

     /**
      * A callback that tells the implementer of this interface that one of the scheduled chores is
      * missing its start time. The implication of a chore missing its start time is that the
      * service's current means of scheduling may not be sufficient to handle the number of ongoing
      * chores (the other explanation is that the chore's execution time is greater than its
      * scheduled period). The service should try to increase its concurrency when this callback is
      * received.
      * @param chore The chore that missed its start time
      */
     public void onChoreMissedStartTime(ScheduledChore chore);
   }

   /**
    * This constructor is for test only. It allows us to create an object and to call chore() on it.
    */
   @InterfaceAudience.Private
   protected ScheduledChore() {
     this("TestChore", null, 0, DEFAULT_INITIAL_DELAY, DEFAULT_TIME_UNIT);
   }

   /**
    * @param name Name assigned to Chore. Useful for identification amongst chores of the same type
    * @param stopper When {@link Stoppable#isStopped()} is true, this chore will cancel and cleanup
    * @param period Period in millis with which this Chore repeats execution when scheduled.
    */
   public ScheduledChore(final String name, Stoppable stopper, final int period) {
     this(name, stopper, period, DEFAULT_INITIAL_DELAY);
   }

   /**
    * @param name Name assigned to Chore. Useful for identification amongst chores of the same type
    * @param stopper When {@link Stoppable#isStopped()} is true, this chore will cancel and cleanup
    * @param period Period in millis with which this Chore repeats execution when scheduled.
    * @param initialDelay Delay before this Chore begins to execute once it has been scheduled. A
    *          value of 0 means the chore will begin to execute immediately. Negative delays are
    *          invalid and will be corrected to a value of 0.
    */
   public ScheduledChore(final String name, Stoppable stopper, final int period,
       final long initialDelay) {
     this(name, stopper, period, initialDelay, DEFAULT_TIME_UNIT);
   }

   /**
    * @param name Name assigned to Chore. Useful for identification amongst chores of the same type
    * @param stopper When {@link Stoppable#isStopped()} is true, this chore will cancel and cleanup
    * @param period Period in Timeunit unit with which this Chore repeats execution when scheduled.
    * @param initialDelay Delay in Timeunit unit before this Chore begins to execute once it has been
    *          scheduled. A value of 0 means the chore will begin to execute immediately. Negative
    *          delays are invalid and will be corrected to a value of 0.
    * @param unit The unit that is used to measure period and initialDelay
    */
   public ScheduledChore(final String name, Stoppable stopper, final int period,
       final long initialDelay, final TimeUnit unit) {
     this.name = name;
     this.stopper = stopper;
     this.period = period;
     this.initialDelay = initialDelay < 0 ? 0 : initialDelay;
     this.timeUnit = unit;
   }

   /**
    * @see java.lang.Runnable#run()
    */
   @Override
   public void run() {
     updateTimeTrackingBeforeRun();
     if (missedStartTime() && isScheduled()) {
       onChoreMissedStartTime();
       LOG.info("Chore: {} missed its start time", getName());
     } else if (stopper.isStopped() || !isScheduled()) {
       cancel(false);
       cleanup();
       LOG.info("Chore: {} was stopped", getName());
     } else {
       try {
         // TODO: Histogram metrics per chore name.
         // For now, just measure and log if DEBUG level logging is enabled.
         long start = 0;
         if (LOG.isDebugEnabled()) {
           start = System.nanoTime();
         }
         if (!initialChoreComplete) {
           initialChoreComplete = initialChore();
         } else {
           chore();
         }
         if (LOG.isDebugEnabled() && start > 0) {
           long end = System.nanoTime();
           LOG.debug("{} execution time: {} ms.", getName(),
             TimeUnit.NANOSECONDS.toMillis(end - start));
         }
       } catch (Throwable t) {
         LOG.error("Caught error", t);
         if (this.stopper.isStopped()) {
           cancel(false);
           cleanup();
         }
       }
     }
   }

   /**
    * Update our time tracking members. Called at the start of an execution of this chore's run()
    * method so that a correct decision can be made as to whether or not we missed the start time
    */
   private synchronized void updateTimeTrackingBeforeRun() {
     timeOfLastRun = timeOfThisRun;
     timeOfThisRun = System.currentTimeMillis();
   }

   /**
    * Notify the ChoreService that this chore has missed its start time. Allows the ChoreService to
    * make the decision as to whether or not it would be worthwhile to increase the number of core
    * pool threads
    */
   private synchronized void onChoreMissedStartTime() {
     if (choreServicer != null) choreServicer.onChoreMissedStartTime(this);
   }

   /**
    * @return How long in millis has it been since this chore last run. Useful for checking if the
    *         chore has missed its scheduled start time by too large of a margin
    */
   synchronized long getTimeBetweenRuns() {
     return timeOfThisRun - timeOfLastRun;
   }

   /**
    * @return true when the time between runs exceeds the acceptable threshold
    */
   private synchronized boolean missedStartTime() {
     return isValidTime(timeOfLastRun) && isValidTime(timeOfThisRun)
         && getTimeBetweenRuns() > getMaximumAllowedTimeBetweenRuns();
   }

   /**
    * @return max allowed time in millis between runs.
    */
   private double getMaximumAllowedTimeBetweenRuns() {
     // Threshold used to determine if the Chore's current run started too late
     return 1.5 * timeUnit.toMillis(period);
   }

   /**
    * @param time in system millis
    * @return true if time is earlier or equal to current milli time
    */
   private synchronized boolean isValidTime(final long time) {
     return time > 0 && time <= System.currentTimeMillis();
   }

   /**
    * @return false when the Chore is not currently scheduled with a ChoreService
    */
   public synchronized boolean triggerNow() {
     if (choreServicer != null) {
       return choreServicer.triggerNow(this);
     } else {
       return false;
     }
   }

   synchronized void setChoreServicer(ChoreServicer service) {
     // Chores should only ever be scheduled with a single ChoreService. If the choreServicer
     // is changing, cancel any existing schedules of this chore.
     if (choreServicer != null && choreServicer != service) {
       choreServicer.cancelChore(this, false);
     }
     choreServicer = service;
     timeOfThisRun = -1;
   }

   public synchronized void cancel() {
     cancel(true);
   }

   public synchronized void cancel(boolean mayInterruptIfRunning) {
     if (isScheduled()) choreServicer.cancelChore(this, mayInterruptIfRunning);

     choreServicer = null;
   }

   public String getName() {
     return name;
   }

   public Stoppable getStopper() {
     return stopper;
   }

   /**
    * @return period to execute chore in getTimeUnit() units
    */
   public int getPeriod() {
     return period;
   }

   /**
    * @return initial delay before executing chore in getTimeUnit() units
    */
   public long getInitialDelay() {
     return initialDelay;
   }

   public TimeUnit getTimeUnit() {
     return timeUnit;
   }

   public synchronized boolean isInitialChoreComplete() {
     return initialChoreComplete;
   }

   @InterfaceAudience.Private
   synchronized ChoreServicer getChoreServicer() {
     return choreServicer;
   }

   @InterfaceAudience.Private
   synchronized long getTimeOfLastRun() {
     return timeOfLastRun;
   }

   @InterfaceAudience.Private
   synchronized long getTimeOfThisRun() {
     return timeOfThisRun;
   }

   /**
    * @return true when this Chore is scheduled with a ChoreService
    */
   public synchronized boolean isScheduled() {
     return choreServicer != null && choreServicer.isChoreScheduled(this);
   }

   @InterfaceAudience.Private
   public synchronized void choreForTesting() {
     chore();
   }

   /**
    * The task to execute on each scheduled execution of the Chore
    */
   protected abstract void chore();

   /**
    * Override to run a task before we start looping.
    * @return true if initial chore was successful
    */
   protected boolean initialChore() {
     // Default does nothing
     return true;
   }

   /**
    * Override to run cleanup tasks when the Chore encounters an error and must stop running
    */
   protected synchronized void cleanup() {
   }

   /**
    * A summation of this chore in human readable format. Downstream users should not presume
    * parsing of this string can relaibly be done between versions. Instead, they should rely
    * on the public accessor methods to get the information they desire.
    */
   @InterfaceAudience.Private
   @Override
   public String toString() {
     return "ScheduledChore name=" + getName() + ", period=" + getPeriod() +
       ", unit=" + getTimeUnit();
   }
 }
	/**
	*
	* 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.hadoop.hbase;

	import java.util.concurrent.ScheduledThreadPoolExecutor;
	import java.util.concurrent.TimeUnit;
	import org.apache.yetus.audience.InterfaceAudience;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;

	/**
	* ScheduledChore is a task performed on a period in hbase. ScheduledChores become active once
	* scheduled with a {@link ChoreService} via {@link ChoreService#scheduleChore(ScheduledChore)}. The
	* chore is run in a {@link ScheduledThreadPoolExecutor} and competes with other ScheduledChores for
	* access to the threads in the core thread pool. If an unhandled exception occurs, the chore
	* cancellation is logged. Implementers should consider whether or not the Chore will be able to
	* execute within the defined period. It is bad practice to define a ScheduledChore whose execution
	* time exceeds its period since it will try to hog one of the threads in the {@link ChoreService}'s
	* thread pool.
	* <p>
	* Don't subclass ScheduledChore if the task relies on being woken up for something to do, such as
	* an entry being added to a queue, etc.
	*/
	@InterfaceAudience.Public
	public abstract class ScheduledChore implements Runnable {
	private static final Logger LOG = LoggerFactory.getLogger(ScheduledChore.class);

	private final String name;

	/**
	* Default values for scheduling parameters should they be excluded during construction
	*/
	private final static TimeUnit DEFAULT_TIME_UNIT = TimeUnit.MILLISECONDS;
	private final static long DEFAULT_INITIAL_DELAY = 0;

	/**
	* Scheduling parameters. Used by ChoreService when scheduling the chore to run periodically
	*/
	private final int period; // in TimeUnit units
	private final TimeUnit timeUnit;
	private final long initialDelay; // in TimeUnit units

	/**
	* Interface to the ChoreService that this ScheduledChore is scheduled with. null if the chore is
	* not scheduled.
	*/
	private ChoreServicer choreServicer;

	/**
	* Variables that encapsulate the meaningful state information
	*/
	private long timeOfLastRun = -1; // system time millis
	private long timeOfThisRun = -1; // system time millis
	private boolean initialChoreComplete = false;

	/**
	* A means by which a ScheduledChore can be stopped. Once a chore recognizes that it has been
	* stopped, it will cancel itself. This is particularly useful in the case where a single stopper
	* instance is given to multiple chores. In such a case, a single {@link Stoppable#stop(String)}
	* command can cause many chores to stop together.
	*/
	private final Stoppable stopper;

	interface ChoreServicer {
	/**
	* Cancel any ongoing schedules that this chore has with the implementer of this interface.
	*/
	public void cancelChore(ScheduledChore chore);
	public void cancelChore(ScheduledChore chore, boolean mayInterruptIfRunning);

	/**
	* @return true when the chore is scheduled with the implementer of this interface
	*/
	public boolean isChoreScheduled(ScheduledChore chore);

	/**
	* This method tries to execute the chore immediately. If the chore is executing at the time of
	* this call, the chore will begin another execution as soon as the current execution finishes
	* <p>
	* If the chore is not scheduled with a ChoreService, this call will fail.
	* @return false when the chore could not be triggered immediately
	*/
	public boolean triggerNow(ScheduledChore chore);

	/**
	* A callback that tells the implementer of this interface that one of the scheduled chores is
	* missing its start time. The implication of a chore missing its start time is that the
	* service's current means of scheduling may not be sufficient to handle the number of ongoing
	* chores (the other explanation is that the chore's execution time is greater than its
	* scheduled period). The service should try to increase its concurrency when this callback is
	* received.
	* @param chore The chore that missed its start time
	*/
	public void onChoreMissedStartTime(ScheduledChore chore);
	}

	/**
	* This constructor is for test only. It allows us to create an object and to call chore() on it.
	*/
	@InterfaceAudience.Private
	protected ScheduledChore() {
	this("TestChore", null, 0, DEFAULT_INITIAL_DELAY, DEFAULT_TIME_UNIT);
	}

	/**
	* @param name Name assigned to Chore. Useful for identification amongst chores of the same type
	* @param stopper When {@link Stoppable#isStopped()} is true, this chore will cancel and cleanup
	* @param period Period in millis with which this Chore repeats execution when scheduled.
	*/
	public ScheduledChore(final String name, Stoppable stopper, final int period) {
	this(name, stopper, period, DEFAULT_INITIAL_DELAY);
	}

	/**
	* @param name Name assigned to Chore. Useful for identification amongst chores of the same type
	* @param stopper When {@link Stoppable#isStopped()} is true, this chore will cancel and cleanup
	* @param period Period in millis with which this Chore repeats execution when scheduled.
	* @param initialDelay Delay before this Chore begins to execute once it has been scheduled. A
	* value of 0 means the chore will begin to execute immediately. Negative delays are
	* invalid and will be corrected to a value of 0.
	*/
	public ScheduledChore(final String name, Stoppable stopper, final int period,
	final long initialDelay) {
	this(name, stopper, period, initialDelay, DEFAULT_TIME_UNIT);
	}

	/**
	* @param name Name assigned to Chore. Useful for identification amongst chores of the same type
	* @param stopper When {@link Stoppable#isStopped()} is true, this chore will cancel and cleanup
	* @param period Period in Timeunit unit with which this Chore repeats execution when scheduled.
	* @param initialDelay Delay in Timeunit unit before this Chore begins to execute once it has been
	* scheduled. A value of 0 means the chore will begin to execute immediately. Negative
	* delays are invalid and will be corrected to a value of 0.
	* @param unit The unit that is used to measure period and initialDelay
	*/
	public ScheduledChore(final String name, Stoppable stopper, final int period,
	final long initialDelay, final TimeUnit unit) {
	this.name = name;
	this.stopper = stopper;
	this.period = period;
	this.initialDelay = initialDelay < 0 ? 0 : initialDelay;
	this.timeUnit = unit;
	}

	/**
	* @see java.lang.Runnable#run()
	*/
	@Override
	public void run() {
	updateTimeTrackingBeforeRun();
	if (missedStartTime() && isScheduled()) {
	onChoreMissedStartTime();
	LOG.info("Chore: {} missed its start time", getName());
	} else if (stopper.isStopped() \|\| !isScheduled()) {
	cancel(false);
	cleanup();
	LOG.info("Chore: {} was stopped", getName());
	} else {
	try {
	// TODO: Histogram metrics per chore name.
	// For now, just measure and log if DEBUG level logging is enabled.
	long start = 0;
	if (LOG.isDebugEnabled()) {
	start = System.nanoTime();
	}
	if (!initialChoreComplete) {
	initialChoreComplete = initialChore();
	} else {
	chore();
	}
	if (LOG.isDebugEnabled() && start > 0) {
	long end = System.nanoTime();
	LOG.debug("{} execution time: {} ms.", getName(),
	TimeUnit.NANOSECONDS.toMillis(end - start));
	}
	} catch (Throwable t) {
	LOG.error("Caught error", t);
	if (this.stopper.isStopped()) {
	cancel(false);
	cleanup();
	}
	}
	}
	}

	/**
	* Update our time tracking members. Called at the start of an execution of this chore's run()
	* method so that a correct decision can be made as to whether or not we missed the start time
	*/
	private synchronized void updateTimeTrackingBeforeRun() {
	timeOfLastRun = timeOfThisRun;
	timeOfThisRun = System.currentTimeMillis();
	}

	/**
	* Notify the ChoreService that this chore has missed its start time. Allows the ChoreService to
	* make the decision as to whether or not it would be worthwhile to increase the number of core
	* pool threads
	*/
	private synchronized void onChoreMissedStartTime() {
	if (choreServicer != null) choreServicer.onChoreMissedStartTime(this);
	}

	/**
	* @return How long in millis has it been since this chore last run. Useful for checking if the
	* chore has missed its scheduled start time by too large of a margin
	*/
	synchronized long getTimeBetweenRuns() {
	return timeOfThisRun - timeOfLastRun;
	}

	/**
	* @return true when the time between runs exceeds the acceptable threshold
	*/
	private synchronized boolean missedStartTime() {
	return isValidTime(timeOfLastRun) && isValidTime(timeOfThisRun)
	&& getTimeBetweenRuns() > getMaximumAllowedTimeBetweenRuns();
	}

	/**
	* @return max allowed time in millis between runs.
	*/
	private double getMaximumAllowedTimeBetweenRuns() {
	// Threshold used to determine if the Chore's current run started too late
	return 1.5 * timeUnit.toMillis(period);
	}

	/**
	* @param time in system millis
	* @return true if time is earlier or equal to current milli time
	*/
	private synchronized boolean isValidTime(final long time) {
	return time > 0 && time <= System.currentTimeMillis();
	}

	/**
	* @return false when the Chore is not currently scheduled with a ChoreService
	*/
	public synchronized boolean triggerNow() {
	if (choreServicer != null) {
	return choreServicer.triggerNow(this);
	} else {
	return false;
	}
	}

	synchronized void setChoreServicer(ChoreServicer service) {
	// Chores should only ever be scheduled with a single ChoreService. If the choreServicer
	// is changing, cancel any existing schedules of this chore.
	if (choreServicer != null && choreServicer != service) {
	choreServicer.cancelChore(this, false);
	}
	choreServicer = service;
	timeOfThisRun = -1;
	}

	public synchronized void cancel() {
	cancel(true);
	}

	public synchronized void cancel(boolean mayInterruptIfRunning) {
	if (isScheduled()) choreServicer.cancelChore(this, mayInterruptIfRunning);

	choreServicer = null;
	}

	public String getName() {
	return name;
	}

	public Stoppable getStopper() {
	return stopper;
	}

	/**
	* @return period to execute chore in getTimeUnit() units
	*/
	public int getPeriod() {
	return period;
	}

	/**
	* @return initial delay before executing chore in getTimeUnit() units
	*/
	public long getInitialDelay() {
	return initialDelay;
	}

	public TimeUnit getTimeUnit() {
	return timeUnit;
	}

	public synchronized boolean isInitialChoreComplete() {
	return initialChoreComplete;
	}

	@InterfaceAudience.Private
	synchronized ChoreServicer getChoreServicer() {
	return choreServicer;
	}

	@InterfaceAudience.Private
	synchronized long getTimeOfLastRun() {
	return timeOfLastRun;
	}

	@InterfaceAudience.Private
	synchronized long getTimeOfThisRun() {
	return timeOfThisRun;
	}

	/**
	* @return true when this Chore is scheduled with a ChoreService
	*/
	public synchronized boolean isScheduled() {
	return choreServicer != null && choreServicer.isChoreScheduled(this);
	}

	@InterfaceAudience.Private
	public synchronized void choreForTesting() {
	chore();
	}

	/**
	* The task to execute on each scheduled execution of the Chore
	*/
	protected abstract void chore();

	/**
	* Override to run a task before we start looping.
	* @return true if initial chore was successful
	*/
	protected boolean initialChore() {
	// Default does nothing
	return true;
	}

	/**
	* Override to run cleanup tasks when the Chore encounters an error and must stop running
	*/
	protected synchronized void cleanup() {
	}

	/**
	* A summation of this chore in human readable format. Downstream users should not presume
	* parsing of this string can relaibly be done between versions. Instead, they should rely
	* on the public accessor methods to get the information they desire.
	*/
	@InterfaceAudience.Private
	@Override
	public String toString() {
	return "ScheduledChore name=" + getName() + ", period=" + getPeriod() +
	", unit=" + getTimeUnit();
	}
	}