curator-recipes/src/main/java/org/apache/curator/framework/recipes/locks/Reaper.java - curator - 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.curator.framework.recipes.locks;

 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Maps;
 import org.apache.curator.framework.CuratorFramework;
 import org.apache.curator.framework.recipes.leader.LeaderLatch;
 import org.apache.curator.framework.recipes.leader.LeaderLatchListener;
 import org.apache.curator.utils.CloseableScheduledExecutorService;
 import org.apache.curator.utils.ThreadUtils;
 import org.apache.zookeeper.CreateMode;
 import org.apache.zookeeper.KeeperException;
 import org.apache.zookeeper.data.Stat;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import java.io.Closeable;
 import java.io.IOException;
 import java.util.Map;
 import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;

 /**
  * Utility to clean up parent lock nodes so that they don't stay around as garbage
  *
  * @deprecated Since 2.9.0 - Reaper/ChildReaper are no longer needed. Use {@link CreateMode#CONTAINER}.
  * Also, all Curator recipes create container parents.
  */
 @Deprecated
 public class Reaper implements Closeable
 {
     private final Logger log = LoggerFactory.getLogger(getClass());
     private final CuratorFramework client;
     private final CloseableScheduledExecutorService executor;
     private final int reapingThresholdMs;
     private final Map<String, PathHolder> activePaths = Maps.newConcurrentMap();
     private final AtomicReference<State> state = new AtomicReference<State>(State.LATENT);
     private final LeaderLatch leaderLatch;
     private final AtomicBoolean reapingIsActive = new AtomicBoolean(true);
     private final boolean ownsLeaderLatch;

     private enum State
     {
         LATENT,
         STARTED,
         CLOSED
     }

     static final int DEFAULT_REAPING_THRESHOLD_MS = (int)TimeUnit.MILLISECONDS.convert(5, TimeUnit.MINUTES);

     @VisibleForTesting
     static final int EMPTY_COUNT_THRESHOLD = 3;

     @VisibleForTesting
     class PathHolder implements Runnable
     {
         final String path;
         final Mode mode;
         final int emptyCount;

         @Override
         public void run()
         {
             reap(this);
         }

         private PathHolder(String path, Mode mode, int emptyCount)
         {
             this.path = path;
             this.mode = mode;
             this.emptyCount = emptyCount;
         }
     }

     public enum Mode
     {
         /**
          * Reap forever, or until removePath is called for the path
          */
         REAP_INDEFINITELY,

         /**
          * Reap until the Reaper succeeds in deleting the path
          */
         REAP_UNTIL_DELETE,

         /**
          * Reap until the path no longer exists
          */
         REAP_UNTIL_GONE
     }

     /**
      * Uses the default reaping threshold of 5 minutes and creates an internal thread pool
      *
      * @param client client
      */
     public Reaper(CuratorFramework client)
     {
         this(client, newExecutorService(), DEFAULT_REAPING_THRESHOLD_MS, (String) null);
     }

     /**
      * Uses the given reaping threshold and creates an internal thread pool
      *
      * @param client             client
      * @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
      */
     public Reaper(CuratorFramework client, int reapingThresholdMs)
     {
         this(client, newExecutorService(), reapingThresholdMs, (String) null);
     }

     /**
      * @param client             client
      * @param executor           thread pool
      * @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
      */
     public Reaper(CuratorFramework client, ScheduledExecutorService executor, int reapingThresholdMs)
     {
         this(client, executor, reapingThresholdMs, (String) null);
     }

     /**
      * @param client             client
      * @param executor           thread pool
      * @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
      * @param leaderPath         if not null, uses a leader selection so that only 1 reaper is active in the cluster
      */
     public Reaper(CuratorFramework client, ScheduledExecutorService executor, int reapingThresholdMs, String leaderPath)
     {
         this(client, executor, reapingThresholdMs, makeLeaderLatchIfPathNotNull(client, leaderPath), true);
     }

     /**
      * @param client             client
      * @param executor           thread pool
      * @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
      * @param leaderLatch        a pre-created leader latch to ensure only 1 reaper is active in the cluster
      */
     public Reaper(CuratorFramework client, ScheduledExecutorService executor, int reapingThresholdMs, LeaderLatch leaderLatch)
     {
         this(client, executor, reapingThresholdMs, leaderLatch, false);
     }

     /**
      * @param client             client
      * @param executor           thread pool
      * @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
      * @param leaderLatch        a pre-created leader latch to ensure only 1 reaper is active in the cluster
      * @param ownsLeaderLatch    indicates whether or not the reaper owns the leader latch (if it exists) and thus should start/stop it
      * */
     private Reaper(CuratorFramework client, ScheduledExecutorService executor, int reapingThresholdMs, LeaderLatch leaderLatch, boolean ownsLeaderLatch)
     {
         this.client = client;
         this.executor = new CloseableScheduledExecutorService(executor);
         this.reapingThresholdMs = reapingThresholdMs / EMPTY_COUNT_THRESHOLD;
         this.leaderLatch = leaderLatch;
         if (leaderLatch != null)
         {
             addListenerToLeaderLatch(leaderLatch);
         }
         this.ownsLeaderLatch = ownsLeaderLatch;
     }


     /**
      * Add a path (using Mode.REAP_INDEFINITELY) to be checked by the reaper. The path will be checked periodically
      * until the reaper is closed.
      *
      * @param path path to check
      */
     public void addPath(String path)
     {
         addPath(path, Mode.REAP_INDEFINITELY);
     }

     /**
      * Add a path to be checked by the reaper. The path will be checked periodically
      * until the reaper is closed, or until the point specified by the Mode
      *
      * @param path path to check
      * @param mode reaping mode
      */
     public void addPath(String path, Mode mode)
     {
         PathHolder pathHolder = new PathHolder(path, mode, 0);
         activePaths.put(path, pathHolder);
         schedule(pathHolder, reapingThresholdMs);
     }

     /**
      * Stop reaping the given path
      *
      * @param path path to remove
      * @return true if the path was removed
      */
     public boolean removePath(String path)
     {
         return activePaths.remove(path) != null;
     }

     /**
      * The reaper must be started
      *
      * @throws Exception errors
      */
     public void start() throws Exception
     {
         Preconditions.checkState(state.compareAndSet(State.LATENT, State.STARTED), "Cannot be started more than once");

         if ( leaderLatch != null && ownsLeaderLatch)
         {
             leaderLatch.start();
         }
     }

     @Override
     public void close() throws IOException
     {
         if ( state.compareAndSet(State.STARTED, State.CLOSED) )
         {
             executor.close();
             if ( leaderLatch != null && ownsLeaderLatch )
             {
                 leaderLatch.close();
             }
         }
     }

     @VisibleForTesting
     protected Future<?> schedule(PathHolder pathHolder, int reapingThresholdMs)
     {
         if ( reapingIsActive.get() )
         {
             return executor.schedule(pathHolder, reapingThresholdMs, TimeUnit.MILLISECONDS);
         }
         return null;
     }

     @VisibleForTesting
     protected void reap(PathHolder holder)
     {
         if ( !activePaths.containsKey(holder.path) )
         {
             return;
         }

         boolean addBack = true;
         int newEmptyCount = 0;
         try
         {
             Stat stat = client.checkExists().forPath(holder.path);
             if ( stat != null ) // otherwise already deleted
             {
                 if ( stat.getNumChildren() == 0 )
                 {
                     if ( (holder.emptyCount + 1) >= EMPTY_COUNT_THRESHOLD )
                     {
                         try
                         {
                             client.delete().forPath(holder.path);
                             log.info("Reaping path: " + holder.path);
                             if ( holder.mode == Mode.REAP_UNTIL_DELETE || holder.mode == Mode.REAP_UNTIL_GONE )
                             {
                                 addBack = false;
                             }
                         }
                         catch ( KeeperException.NoNodeException ignore )
                         {
                             // Node must have been deleted by another process/thread
                             if ( holder.mode == Mode.REAP_UNTIL_GONE )
                             {
                                 addBack = false;
                             }
                         }
                         catch ( KeeperException.NotEmptyException ignore )
                         {
                             // ignore - it must have been re-used
                         }
                     }
                     else
                     {
                         newEmptyCount = holder.emptyCount + 1;
                     }
                 }
             }
             else
             {
                 if ( holder.mode == Mode.REAP_UNTIL_GONE )
                 {
                     addBack = false;
                 }
             }
         }
         catch ( Exception e )
         {
             log.error("Trying to reap: " + holder.path, e);
         }

         if ( !addBack )
         {
             activePaths.remove(holder.path);
         }
         else if ( !Thread.currentThread().isInterrupted() && (state.get() == State.STARTED) && activePaths.containsKey(holder.path) )
         {
             activePaths.put(holder.path, holder);
             schedule(new PathHolder(holder.path, holder.mode, newEmptyCount), reapingThresholdMs);
         }
     }

     /**
      * Allocate an executor service for the reaper
      *
      * @return service
      */
     public static ScheduledExecutorService newExecutorService()
     {
         return ThreadUtils.newSingleThreadScheduledExecutor("Reaper");
     }

     private void addListenerToLeaderLatch(LeaderLatch leaderLatch)
     {

         LeaderLatchListener listener = new LeaderLatchListener()
         {
             @Override
             public void isLeader()
             {
                 reapingIsActive.set(true);
                 for ( PathHolder holder : activePaths.values() )
                 {
                     schedule(holder, reapingThresholdMs);
                 }
             }

             @Override
             public void notLeader()
             {
                 reapingIsActive.set(false);
             }
         };
         leaderLatch.addListener(listener);

         reapingIsActive.set(leaderLatch.hasLeadership());
     }

     private static LeaderLatch makeLeaderLatchIfPathNotNull(CuratorFramework client, String leaderPath)
     {
         if (leaderPath == null)
         {
             return null;
         }
         else
         {
             return new LeaderLatch(client, leaderPath);
         }
     }
 }
	/**
	* 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.curator.framework.recipes.locks;

	import com.google.common.annotations.VisibleForTesting;
	import com.google.common.base.Preconditions;
	import com.google.common.collect.Maps;
	import org.apache.curator.framework.CuratorFramework;
	import org.apache.curator.framework.recipes.leader.LeaderLatch;
	import org.apache.curator.framework.recipes.leader.LeaderLatchListener;
	import org.apache.curator.utils.CloseableScheduledExecutorService;
	import org.apache.curator.utils.ThreadUtils;
	import org.apache.zookeeper.CreateMode;
	import org.apache.zookeeper.KeeperException;
	import org.apache.zookeeper.data.Stat;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;
	import java.io.Closeable;
	import java.io.IOException;
	import java.util.Map;
	import java.util.concurrent.Future;
	import java.util.concurrent.ScheduledExecutorService;
	import java.util.concurrent.TimeUnit;
	import java.util.concurrent.atomic.AtomicBoolean;
	import java.util.concurrent.atomic.AtomicReference;

	/**
	* Utility to clean up parent lock nodes so that they don't stay around as garbage
	*
	* @deprecated Since 2.9.0 - Reaper/ChildReaper are no longer needed. Use {@link CreateMode#CONTAINER}.
	* Also, all Curator recipes create container parents.
	*/
	@Deprecated
	public class Reaper implements Closeable
	{
	private final Logger log = LoggerFactory.getLogger(getClass());
	private final CuratorFramework client;
	private final CloseableScheduledExecutorService executor;
	private final int reapingThresholdMs;
	private final Map<String, PathHolder> activePaths = Maps.newConcurrentMap();
	private final AtomicReference<State> state = new AtomicReference<State>(State.LATENT);
	private final LeaderLatch leaderLatch;
	private final AtomicBoolean reapingIsActive = new AtomicBoolean(true);
	private final boolean ownsLeaderLatch;

	private enum State
	{
	LATENT,
	STARTED,
	CLOSED
	}

	static final int DEFAULT_REAPING_THRESHOLD_MS = (int)TimeUnit.MILLISECONDS.convert(5, TimeUnit.MINUTES);

	@VisibleForTesting
	static final int EMPTY_COUNT_THRESHOLD = 3;

	@VisibleForTesting
	class PathHolder implements Runnable
	{
	final String path;
	final Mode mode;
	final int emptyCount;

	@Override
	public void run()
	{
	reap(this);
	}

	private PathHolder(String path, Mode mode, int emptyCount)
	{
	this.path = path;
	this.mode = mode;
	this.emptyCount = emptyCount;
	}
	}

	public enum Mode
	{
	/**
	* Reap forever, or until removePath is called for the path
	*/
	REAP_INDEFINITELY,

	/**
	* Reap until the Reaper succeeds in deleting the path
	*/
	REAP_UNTIL_DELETE,

	/**
	* Reap until the path no longer exists
	*/
	REAP_UNTIL_GONE
	}

	/**
	* Uses the default reaping threshold of 5 minutes and creates an internal thread pool
	*
	* @param client client
	*/
	public Reaper(CuratorFramework client)
	{
	this(client, newExecutorService(), DEFAULT_REAPING_THRESHOLD_MS, (String) null);
	}

	/**
	* Uses the given reaping threshold and creates an internal thread pool
	*
	* @param client client
	* @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
	*/
	public Reaper(CuratorFramework client, int reapingThresholdMs)
	{
	this(client, newExecutorService(), reapingThresholdMs, (String) null);
	}

	/**
	* @param client client
	* @param executor thread pool
	* @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
	*/
	public Reaper(CuratorFramework client, ScheduledExecutorService executor, int reapingThresholdMs)
	{
	this(client, executor, reapingThresholdMs, (String) null);
	}

	/**
	* @param client client
	* @param executor thread pool
	* @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
	* @param leaderPath if not null, uses a leader selection so that only 1 reaper is active in the cluster
	*/
	public Reaper(CuratorFramework client, ScheduledExecutorService executor, int reapingThresholdMs, String leaderPath)
	{
	this(client, executor, reapingThresholdMs, makeLeaderLatchIfPathNotNull(client, leaderPath), true);
	}

	/**
	* @param client client
	* @param executor thread pool
	* @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
	* @param leaderLatch a pre-created leader latch to ensure only 1 reaper is active in the cluster
	*/
	public Reaper(CuratorFramework client, ScheduledExecutorService executor, int reapingThresholdMs, LeaderLatch leaderLatch)
	{
	this(client, executor, reapingThresholdMs, leaderLatch, false);
	}

	/**
	* @param client client
	* @param executor thread pool
	* @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
	* @param leaderLatch a pre-created leader latch to ensure only 1 reaper is active in the cluster
	* @param ownsLeaderLatch indicates whether or not the reaper owns the leader latch (if it exists) and thus should start/stop it
	* */
	private Reaper(CuratorFramework client, ScheduledExecutorService executor, int reapingThresholdMs, LeaderLatch leaderLatch, boolean ownsLeaderLatch)
	{
	this.client = client;
	this.executor = new CloseableScheduledExecutorService(executor);
	this.reapingThresholdMs = reapingThresholdMs / EMPTY_COUNT_THRESHOLD;
	this.leaderLatch = leaderLatch;
	if (leaderLatch != null)
	{
	addListenerToLeaderLatch(leaderLatch);
	}
	this.ownsLeaderLatch = ownsLeaderLatch;
	}


	/**
	* Add a path (using Mode.REAP_INDEFINITELY) to be checked by the reaper. The path will be checked periodically
	* until the reaper is closed.
	*
	* @param path path to check
	*/
	public void addPath(String path)
	{
	addPath(path, Mode.REAP_INDEFINITELY);
	}

	/**
	* Add a path to be checked by the reaper. The path will be checked periodically
	* until the reaper is closed, or until the point specified by the Mode
	*
	* @param path path to check
	* @param mode reaping mode
	*/
	public void addPath(String path, Mode mode)
	{
	PathHolder pathHolder = new PathHolder(path, mode, 0);
	activePaths.put(path, pathHolder);
	schedule(pathHolder, reapingThresholdMs);
	}

	/**
	* Stop reaping the given path
	*
	* @param path path to remove
	* @return true if the path was removed
	*/
	public boolean removePath(String path)
	{
	return activePaths.remove(path) != null;
	}

	/**
	* The reaper must be started
	*
	* @throws Exception errors
	*/
	public void start() throws Exception
	{
	Preconditions.checkState(state.compareAndSet(State.LATENT, State.STARTED), "Cannot be started more than once");

	if ( leaderLatch != null && ownsLeaderLatch)
	{
	leaderLatch.start();
	}
	}

	@Override
	public void close() throws IOException
	{
	if ( state.compareAndSet(State.STARTED, State.CLOSED) )
	{
	executor.close();
	if ( leaderLatch != null && ownsLeaderLatch )
	{
	leaderLatch.close();
	}
	}
	}

	@VisibleForTesting
	protected Future<?> schedule(PathHolder pathHolder, int reapingThresholdMs)
	{
	if ( reapingIsActive.get() )
	{
	return executor.schedule(pathHolder, reapingThresholdMs, TimeUnit.MILLISECONDS);
	}
	return null;
	}

	@VisibleForTesting
	protected void reap(PathHolder holder)
	{
	if ( !activePaths.containsKey(holder.path) )
	{
	return;
	}

	boolean addBack = true;
	int newEmptyCount = 0;
	try
	{
	Stat stat = client.checkExists().forPath(holder.path);
	if ( stat != null ) // otherwise already deleted
	{
	if ( stat.getNumChildren() == 0 )
	{
	if ( (holder.emptyCount + 1) >= EMPTY_COUNT_THRESHOLD )
	{
	try
	{
	client.delete().forPath(holder.path);
	log.info("Reaping path: " + holder.path);
	if ( holder.mode == Mode.REAP_UNTIL_DELETE \|\| holder.mode == Mode.REAP_UNTIL_GONE )
	{
	addBack = false;
	}
	}
	catch ( KeeperException.NoNodeException ignore )
	{
	// Node must have been deleted by another process/thread
	if ( holder.mode == Mode.REAP_UNTIL_GONE )
	{
	addBack = false;
	}
	}
	catch ( KeeperException.NotEmptyException ignore )
	{
	// ignore - it must have been re-used
	}
	}
	else
	{
	newEmptyCount = holder.emptyCount + 1;
	}
	}
	}
	else
	{
	if ( holder.mode == Mode.REAP_UNTIL_GONE )
	{
	addBack = false;
	}
	}
	}
	catch ( Exception e )
	{
	log.error("Trying to reap: " + holder.path, e);
	}

	if ( !addBack )
	{
	activePaths.remove(holder.path);
	}
	else if ( !Thread.currentThread().isInterrupted() && (state.get() == State.STARTED) && activePaths.containsKey(holder.path) )
	{
	activePaths.put(holder.path, holder);
	schedule(new PathHolder(holder.path, holder.mode, newEmptyCount), reapingThresholdMs);
	}
	}

	/**
	* Allocate an executor service for the reaper
	*
	* @return service
	*/
	public static ScheduledExecutorService newExecutorService()
	{
	return ThreadUtils.newSingleThreadScheduledExecutor("Reaper");
	}

	private void addListenerToLeaderLatch(LeaderLatch leaderLatch)
	{

	LeaderLatchListener listener = new LeaderLatchListener()
	{
	@Override
	public void isLeader()
	{
	reapingIsActive.set(true);
	for ( PathHolder holder : activePaths.values() )
	{
	schedule(holder, reapingThresholdMs);
	}
	}

	@Override
	public void notLeader()
	{
	reapingIsActive.set(false);
	}
	};
	leaderLatch.addListener(listener);

	reapingIsActive.set(leaderLatch.hasLeadership());
	}

	private static LeaderLatch makeLeaderLatchIfPathNotNull(CuratorFramework client, String leaderPath)
	{
	if (leaderPath == null)
	{
	return null;
	}
	else
	{
	return new LeaderLatch(client, leaderPath);
	}
	}
	}