/**
    * 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.master;
  
  import static org.apache.hadoop.hbase.master.SplitLogManager.ResubmitDirective.CHECK;
  import static org.apache.hadoop.hbase.master.SplitLogManager.ResubmitDirective.FORCE;
  import static org.apache.hadoop.hbase.master.SplitLogManager.TerminationStatus.DELETED;
  import static org.apache.hadoop.hbase.master.SplitLogManager.TerminationStatus.FAILURE;
  import static org.apache.hadoop.hbase.master.SplitLogManager.TerminationStatus.IN_PROGRESS;
  import static org.apache.hadoop.hbase.master.SplitLogManager.TerminationStatus.SUCCESS;
  
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.fs.PathFilter;
  import org.apache.hadoop.hbase.ChoreService;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.ScheduledChore;
  import org.apache.hadoop.hbase.Server;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.SplitLogCounters;
  import org.apache.hadoop.hbase.Stoppable;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.coordination.BaseCoordinatedStateManager;
  import org.apache.hadoop.hbase.coordination.SplitLogManagerCoordination;
  import org.apache.hadoop.hbase.coordination.SplitLogManagerCoordination.SplitLogManagerDetails;
  import org.apache.hadoop.hbase.monitoring.MonitoredTask;
  import org.apache.hadoop.hbase.monitoring.TaskMonitor;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos.SplitLogTask.RecoveryMode;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.util.FSUtils;
  import org.apache.hadoop.hbase.util.Pair;
  import org.apache.hadoop.hbase.wal.DefaultWALProvider;
  import org.apache.hadoop.hbase.wal.WALFactory;
  
  import com.google.common.annotations.VisibleForTesting;
  
  /**
   * Distributes the task of log splitting to the available region servers.
   * Coordination happens via coordination engine. For every log file that has to be split a
   * task is created. SplitLogWorkers race to grab a task.
   *
   * <p>SplitLogManager monitors the tasks that it creates using the
   * timeoutMonitor thread. If a task's progress is slow then
   * {@link SplitLogManagerCoordination#checkTasks} will take away the
   * task from the owner {@link org.apache.hadoop.hbase.regionserver.SplitLogWorker} 
   * and the task will be up for grabs again. When the task is done then it is deleted 
   * by SplitLogManager.
   *
   * <p>Clients call {@link #splitLogDistributed(Path)} to split a region server's
   * log files. The caller thread waits in this method until all the log files
   * have been split.
   *
   * <p>All the coordination calls made by this class are asynchronous. This is mainly
   * to help reduce response time seen by the callers.
   *
   * <p>There is race in this design between the SplitLogManager and the
   * SplitLogWorker. SplitLogManager might re-queue a task that has in reality
   * already been completed by a SplitLogWorker. We rely on the idempotency of
   * the log splitting task for correctness.
   *
   * <p>It is also assumed that every log splitting task is unique and once
   * completed (either with success or with error) it will be not be submitted
   * again. If a task is resubmitted then there is a risk that old "delete task"
   * can delete the re-submission.
   */
  @InterfaceAudience.Private
  public class SplitLogManager {
   private static final Log LOG = LogFactory.getLog(SplitLogManager.class);
 
   private Server server;
 
   private final Stoppable stopper;
   private final Configuration conf;
   private final ChoreService choreService;
 
   public static final int DEFAULT_UNASSIGNED_TIMEOUT = (3 * 60 * 1000); // 3 min
 
   private long unassignedTimeout;
   private long lastTaskCreateTime = Long.MAX_VALUE;
   private long checkRecoveringTimeThreshold = 15000; // 15 seconds
   private final List<Pair<Set<ServerName>, Boolean>> failedRecoveringRegionDeletions = Collections
       .synchronizedList(new ArrayList<Pair<Set<ServerName>, Boolean>>());
 
   /**
    * In distributedLogReplay mode, we need touch both splitlog and recovering-regions znodes in one
    * operation. So the lock is used to guard such cases.
    */
   protected final ReentrantLock recoveringRegionLock = new ReentrantLock();
 
   private final ConcurrentMap<String, Task> tasks = new ConcurrentHashMap<String, Task>();
   private TimeoutMonitor timeoutMonitor;
 
   private volatile Set<ServerName> deadWorkers = null;
   private final Object deadWorkersLock = new Object();
 
   /**
    * Its OK to construct this object even when region-servers are not online. It does lookup the
    * orphan tasks in coordination engine but it doesn't block waiting for them to be done.
    * @param server the server instance
    * @param conf the HBase configuration
    * @param stopper the stoppable in case anything is wrong
    * @param master the master services
    * @param serverName the master server name
    * @throws IOException
    */
   public SplitLogManager(Server server, Configuration conf, Stoppable stopper,
       MasterServices master, ServerName serverName) throws IOException {
     this.server = server;
     this.conf = conf;
     this.stopper = stopper;
     this.choreService = new ChoreService(serverName.toString() + "_splitLogManager_");
     if (server.getCoordinatedStateManager() != null) {
       SplitLogManagerCoordination coordination =
           ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
               .getSplitLogManagerCoordination();
       Set<String> failedDeletions = Collections.synchronizedSet(new HashSet<String>());
       SplitLogManagerDetails details =
           new SplitLogManagerDetails(tasks, master, failedDeletions, serverName);
       coordination.setDetails(details);
       coordination.init();
       // Determine recovery mode
     }
     this.unassignedTimeout =
         conf.getInt("hbase.splitlog.manager.unassigned.timeout", DEFAULT_UNASSIGNED_TIMEOUT);
     this.timeoutMonitor =
         new TimeoutMonitor(conf.getInt("hbase.splitlog.manager.timeoutmonitor.period", 1000),
             stopper);
     choreService.scheduleChore(timeoutMonitor);
   }
 
   private FileStatus[] getFileList(List<Path> logDirs, PathFilter filter) throws IOException {
     return getFileList(conf, logDirs, filter);
   }
 
   /**
    * Get a list of paths that need to be split given a set of server-specific directories and
    * optionally  a filter.
    *
    * See {@link DefaultWALProvider#getServerNameFromWALDirectoryName} for more info on directory
    * layout.
    *
    * Should be package-private, but is needed by
    * {@link org.apache.hadoop.hbase.wal.WALSplitter#split(Path, Path, Path, FileSystem,
    *     Configuration, WALFactory)} for tests.
    */
   @VisibleForTesting
   public static FileStatus[] getFileList(final Configuration conf, final List<Path> logDirs,
       final PathFilter filter)
       throws IOException {
     List<FileStatus> fileStatus = new ArrayList<FileStatus>();
     for (Path logDir : logDirs) {
       final FileSystem fs = logDir.getFileSystem(conf);
       if (!fs.exists(logDir)) {
         LOG.warn(logDir + " doesn't exist. Nothing to do!");
         continue;
       }
       FileStatus[] logfiles = FSUtils.listStatus(fs, logDir, filter);
       if (logfiles == null || logfiles.length == 0) {
         LOG.info(logDir + " is empty dir, no logs to split");
       } else {
         Collections.addAll(fileStatus, logfiles);
       }
     }
     FileStatus[] a = new FileStatus[fileStatus.size()];
     return fileStatus.toArray(a);
   }
 
   /**
    * @param logDir one region sever wal dir path in .logs
    * @throws IOException if there was an error while splitting any log file
    * @return cumulative size of the logfiles split
    * @throws IOException
    */
   public long splitLogDistributed(final Path logDir) throws IOException {
     List<Path> logDirs = new ArrayList<Path>();
     logDirs.add(logDir);
     return splitLogDistributed(logDirs);
   }
 
   /**
    * The caller will block until all the log files of the given region server have been processed -
    * successfully split or an error is encountered - by an available worker region server. This
    * method must only be called after the region servers have been brought online.
    * @param logDirs List of log dirs to split
    * @throws IOException If there was an error while splitting any log file
    * @return cumulative size of the logfiles split
    */
   public long splitLogDistributed(final List<Path> logDirs) throws IOException {
     if (logDirs.isEmpty()) {
       return 0;
     }
     Set<ServerName> serverNames = new HashSet<ServerName>();
     for (Path logDir : logDirs) {
       try {
         ServerName serverName = DefaultWALProvider.getServerNameFromWALDirectoryName(logDir);
         if (serverName != null) {
           serverNames.add(serverName);
         }
       } catch (IllegalArgumentException e) {
         // ignore invalid format error.
         LOG.warn("Cannot parse server name from " + logDir);
       }
     }
     return splitLogDistributed(serverNames, logDirs, null);
   }
 
   /**
    * The caller will block until all the hbase:meta log files of the given region server have been
    * processed - successfully split or an error is encountered - by an available worker region
    * server. This method must only be called after the region servers have been brought online.
    * @param logDirs List of log dirs to split
    * @param filter the Path filter to select specific files for considering
    * @throws IOException If there was an error while splitting any log file
    * @return cumulative size of the logfiles split
    */
   public long splitLogDistributed(final Set<ServerName> serverNames, final List<Path> logDirs,
       PathFilter filter) throws IOException {
     MonitoredTask status = TaskMonitor.get().createStatus("Doing distributed log split in " +
       logDirs + " for serverName=" + serverNames);
     FileStatus[] logfiles = getFileList(logDirs, filter);
     status.setStatus("Checking directory contents...");
     LOG.debug("Scheduling batch of logs to split");
     SplitLogCounters.tot_mgr_log_split_batch_start.incrementAndGet();
     LOG.info("started splitting " + logfiles.length + " logs in " + logDirs +
       " for " + serverNames);
     long t = EnvironmentEdgeManager.currentTime();
     long totalSize = 0;
     TaskBatch batch = new TaskBatch();
     Boolean isMetaRecovery = (filter == null) ? null : false;
     for (FileStatus lf : logfiles) {
       // TODO If the log file is still being written to - which is most likely
       // the case for the last log file - then its length will show up here
       // as zero. The size of such a file can only be retrieved after
       // recover-lease is done. totalSize will be under in most cases and the
       // metrics that it drives will also be under-reported.
       totalSize += lf.getLen();
       String pathToLog = FSUtils.removeRootPath(lf.getPath(), conf);
       if (!enqueueSplitTask(pathToLog, batch)) {
         throw new IOException("duplicate log split scheduled for " + lf.getPath());
       }
     }
     waitForSplittingCompletion(batch, status);
     // remove recovering regions
     if (filter == MasterFileSystem.META_FILTER /* reference comparison */) {
       // we split meta regions and user regions separately therefore logfiles are either all for
       // meta or user regions but won't for both( we could have mixed situations in tests)
       isMetaRecovery = true;
     }
     removeRecoveringRegions(serverNames, isMetaRecovery);
 
     if (batch.done != batch.installed) {
       batch.isDead = true;
       SplitLogCounters.tot_mgr_log_split_batch_err.incrementAndGet();
       LOG.warn("error while splitting logs in " + logDirs + " installed = " + batch.installed
           + " but only " + batch.done + " done");
       String msg = "error or interrupted while splitting logs in " + logDirs + " Task = " + batch;
       status.abort(msg);
       throw new IOException(msg);
     }
     for (Path logDir : logDirs) {
       status.setStatus("Cleaning up log directory...");
       final FileSystem fs = logDir.getFileSystem(conf);
       try {
         if (fs.exists(logDir) && !fs.delete(logDir, false)) {
           LOG.warn("Unable to delete log src dir. Ignoring. " + logDir);
         }
       } catch (IOException ioe) {
         FileStatus[] files = fs.listStatus(logDir);
         if (files != null && files.length > 0) {
           LOG.warn("returning success without actually splitting and "
               + "deleting all the log files in path " + logDir);
         } else {
           LOG.warn("Unable to delete log src dir. Ignoring. " + logDir, ioe);
         }
       }
       SplitLogCounters.tot_mgr_log_split_batch_success.incrementAndGet();
     }
     String msg =
         "finished splitting (more than or equal to) " + totalSize + " bytes in " + batch.installed
             + " log files in " + logDirs + " in "
             + (EnvironmentEdgeManager.currentTime() - t) + "ms";
     status.markComplete(msg);
     LOG.info(msg);
     return totalSize;
   }
 
   /**
    * Add a task entry to coordination if it is not already there.
    * @param taskname the path of the log to be split
    * @param batch the batch this task belongs to
    * @return true if a new entry is created, false if it is already there.
    */
   boolean enqueueSplitTask(String taskname, TaskBatch batch) {
     lastTaskCreateTime = EnvironmentEdgeManager.currentTime();
     String task =
         ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
             .getSplitLogManagerCoordination().prepareTask(taskname);
     Task oldtask = createTaskIfAbsent(task, batch);
     if (oldtask == null) {
       // publish the task in the coordination engine
       ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
           .getSplitLogManagerCoordination().submitTask(task);
       return true;
     }
     return false;
   }
 
   private void waitForSplittingCompletion(TaskBatch batch, MonitoredTask status) {
     synchronized (batch) {
       while ((batch.done + batch.error) != batch.installed) {
         try {
           status.setStatus("Waiting for distributed tasks to finish. " + " scheduled="
               + batch.installed + " done=" + batch.done + " error=" + batch.error);
           int remaining = batch.installed - (batch.done + batch.error);
           int actual = activeTasks(batch);
           if (remaining != actual) {
             LOG.warn("Expected " + remaining + " active tasks, but actually there are " + actual);
           }
           int remainingTasks =
               ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
                   .getSplitLogManagerCoordination().remainingTasksInCoordination();
           if (remainingTasks >= 0 && actual > remainingTasks) {
             LOG.warn("Expected at least" + actual + " tasks remaining, but actually there are "
                 + remainingTasks);
           }
           if (remainingTasks == 0 || actual == 0) {
             LOG.warn("No more task remaining, splitting "
                 + "should have completed. Remaining tasks is " + remainingTasks
                 + ", active tasks in map " + actual);
             if (remainingTasks == 0 && actual == 0) {
               return;
             }
           }
           batch.wait(100);
           if (stopper.isStopped()) {
             LOG.warn("Stopped while waiting for log splits to be completed");
             return;
           }
         } catch (InterruptedException e) {
           LOG.warn("Interrupted while waiting for log splits to be completed");
           Thread.currentThread().interrupt();
           return;
         }
       }
     }
   }
 
   @VisibleForTesting
   ConcurrentMap<String, Task> getTasks() {
     return tasks;
   }
 
   private int activeTasks(final TaskBatch batch) {
     int count = 0;
     for (Task t : tasks.values()) {
       if (t.batch == batch && t.status == TerminationStatus.IN_PROGRESS) {
         count++;
       }
     }
     return count;
 
   }
 
   /**
    * It removes recovering regions under /hbase/recovering-regions/[encoded region name] so that the
    * region server hosting the region can allow reads to the recovered region
    * @param serverNames servers which are just recovered
    * @param isMetaRecovery whether current recovery is for the meta region on
    *          <code>serverNames<code>
    */
   private void removeRecoveringRegions(final Set<ServerName> serverNames, Boolean isMetaRecovery) {
     if (!isLogReplaying()) {
       // the function is only used in WALEdit direct replay mode
       return;
     }
 
     Set<String> recoveredServerNameSet = new HashSet<String>();
     if (serverNames != null) {
       for (ServerName tmpServerName : serverNames) {
         recoveredServerNameSet.add(tmpServerName.getServerName());
       }
     }
 
     try {
       this.recoveringRegionLock.lock();
       ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
           .getSplitLogManagerCoordination().removeRecoveringRegions(recoveredServerNameSet,
             isMetaRecovery);
     } catch (IOException e) {
       LOG.warn("removeRecoveringRegions got exception. Will retry", e);
       if (serverNames != null && !serverNames.isEmpty()) {
         this.failedRecoveringRegionDeletions.add(new Pair<Set<ServerName>, Boolean>(serverNames,
             isMetaRecovery));
       }
     } finally {
       this.recoveringRegionLock.unlock();
     }
   }
 
   /**
    * It removes stale recovering regions under /hbase/recovering-regions/[encoded region name]
    * during master initialization phase.
    * @param failedServers A set of known failed servers
    * @throws IOException
    */
   void removeStaleRecoveringRegions(final Set<ServerName> failedServers) throws IOException,
       InterruptedIOException {
     Set<String> knownFailedServers = new HashSet<String>();
     if (failedServers != null) {
       for (ServerName tmpServerName : failedServers) {
         knownFailedServers.add(tmpServerName.getServerName());
       }
     }
 
     this.recoveringRegionLock.lock();
     try {
       ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
           .getSplitLogManagerCoordination().removeStaleRecoveringRegions(knownFailedServers);
     } finally {
       this.recoveringRegionLock.unlock();
     }
   }
 
   /**
    * @param path
    * @param batch
    * @return null on success, existing task on error
    */
   private Task createTaskIfAbsent(String path, TaskBatch batch) {
     Task oldtask;
     // batch.installed is only changed via this function and
     // a single thread touches batch.installed.
     Task newtask = new Task();
     newtask.batch = batch;
     oldtask = tasks.putIfAbsent(path, newtask);
     if (oldtask == null) {
       batch.installed++;
       return null;
     }
     // new task was not used.
     synchronized (oldtask) {
       if (oldtask.isOrphan()) {
         if (oldtask.status == SUCCESS) {
           // The task is already done. Do not install the batch for this
           // task because it might be too late for setDone() to update
           // batch.done. There is no need for the batch creator to wait for
           // this task to complete.
           return (null);
         }
         if (oldtask.status == IN_PROGRESS) {
           oldtask.batch = batch;
           batch.installed++;
           LOG.debug("Previously orphan task " + path + " is now being waited upon");
           return null;
         }
         while (oldtask.status == FAILURE) {
           LOG.debug("wait for status of task " + path + " to change to DELETED");
           SplitLogCounters.tot_mgr_wait_for_zk_delete.incrementAndGet();
           try {
             oldtask.wait();
           } catch (InterruptedException e) {
             Thread.currentThread().interrupt();
             LOG.warn("Interrupted when waiting for znode delete callback");
             // fall through to return failure
             break;
           }
         }
         if (oldtask.status != DELETED) {
           LOG.warn("Failure because previously failed task"
               + " state still present. Waiting for znode delete callback" + " path=" + path);
           return oldtask;
         }
         // reinsert the newTask and it must succeed this time
         Task t = tasks.putIfAbsent(path, newtask);
         if (t == null) {
           batch.installed++;
           return null;
         }
         LOG.fatal("Logic error. Deleted task still present in tasks map");
         assert false : "Deleted task still present in tasks map";
         return t;
       }
       LOG.warn("Failure because two threads can't wait for the same task; path=" + path);
       return oldtask;
     }
   }
 
   Task findOrCreateOrphanTask(String path) {
     Task orphanTask = new Task();
     Task task;
     task = tasks.putIfAbsent(path, orphanTask);
     if (task == null) {
       LOG.info("creating orphan task " + path);
       SplitLogCounters.tot_mgr_orphan_task_acquired.incrementAndGet();
       task = orphanTask;
     }
     return task;
   }
 
   public void stop() {
     if (choreService != null) {
       choreService.shutdown();
     }
     if (timeoutMonitor != null) {
       timeoutMonitor.cancel(true);
     }
   }
 
   void handleDeadWorker(ServerName workerName) {
     // resubmit the tasks on the TimeoutMonitor thread. Makes it easier
     // to reason about concurrency. Makes it easier to retry.
     synchronized (deadWorkersLock) {
       if (deadWorkers == null) {
         deadWorkers = new HashSet<ServerName>(100);
       }
       deadWorkers.add(workerName);
     }
     LOG.info("dead splitlog worker " + workerName);
   }
 
   void handleDeadWorkers(Set<ServerName> serverNames) {
     synchronized (deadWorkersLock) {
       if (deadWorkers == null) {
         deadWorkers = new HashSet<ServerName>(100);
       }
       deadWorkers.addAll(serverNames);
     }
     LOG.info("dead splitlog workers " + serverNames);
   }
 
   /**
    * This function is to set recovery mode from outstanding split log tasks from before or current
    * configuration setting
    * @param isForInitialization
    * @throws IOException throws if it's impossible to set recovery mode
    */
   public void setRecoveryMode(boolean isForInitialization) throws IOException {
     ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
         .getSplitLogManagerCoordination().setRecoveryMode(isForInitialization);
 
   }
 
   public void markRegionsRecovering(ServerName server, Set<HRegionInfo> userRegions)
       throws InterruptedIOException, IOException {
     if (userRegions == null || (!isLogReplaying())) {
       return;
     }
     try {
       this.recoveringRegionLock.lock();
       // mark that we're creating recovering regions
       ((BaseCoordinatedStateManager) this.server.getCoordinatedStateManager())
           .getSplitLogManagerCoordination().markRegionsRecovering(server, userRegions);
     } finally {
       this.recoveringRegionLock.unlock();
     }
 
   }
 
   /**
    * @return whether log is replaying
    */
   public boolean isLogReplaying() {
     if (server.getCoordinatedStateManager() == null) return false;
     return ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
         .getSplitLogManagerCoordination().isReplaying();
   }
 
   /**
    * @return whether log is splitting
    */
   public boolean isLogSplitting() {
     if (server.getCoordinatedStateManager() == null) return false;
     return ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
         .getSplitLogManagerCoordination().isSplitting();
   }
 
   /**
    * @return the current log recovery mode
    */
   public RecoveryMode getRecoveryMode() {
     return ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
         .getSplitLogManagerCoordination().getRecoveryMode();
   }
 
   /**
    * Keeps track of the batch of tasks submitted together by a caller in splitLogDistributed().
    * Clients threads use this object to wait for all their tasks to be done.
    * <p>
    * All access is synchronized.
    */
   @InterfaceAudience.Private
   public static class TaskBatch {
     public int installed = 0;
     public int done = 0;
     public int error = 0;
     public volatile boolean isDead = false;
 
     @Override
     public String toString() {
       return ("installed = " + installed + " done = " + done + " error = " + error);
     }
   }
 
   /**
    * in memory state of an active task.
    */
   @InterfaceAudience.Private
   public static class Task {
     public volatile long last_update;
     public volatile int last_version;
     public volatile ServerName cur_worker_name;
     public volatile TaskBatch batch;
     public volatile TerminationStatus status;
     public volatile int incarnation;
     public final AtomicInteger unforcedResubmits = new AtomicInteger();
     public volatile boolean resubmitThresholdReached;
 
     @Override
     public String toString() {
       return ("last_update = " + last_update + " last_version = " + last_version
           + " cur_worker_name = " + cur_worker_name + " status = " + status + " incarnation = "
           + incarnation + " resubmits = " + unforcedResubmits.get() + " batch = " + batch);
     }
 
     public Task() {
       incarnation = 0;
       last_version = -1;
       status = IN_PROGRESS;
       setUnassigned();
     }
 
     public boolean isOrphan() {
       return (batch == null || batch.isDead);
     }
 
     public boolean isUnassigned() {
       return (cur_worker_name == null);
     }
 
     public void heartbeatNoDetails(long time) {
       last_update = time;
     }
 
     public void heartbeat(long time, int version, ServerName worker) {
       last_version = version;
       last_update = time;
       cur_worker_name = worker;
     }
 
     public void setUnassigned() {
       cur_worker_name = null;
       last_update = -1;
     }
   }
 
   /**
    * Periodically checks all active tasks and resubmits the ones that have timed out
    */
   private class TimeoutMonitor extends ScheduledChore {
     private long lastLog = 0;
 
     public TimeoutMonitor(final int period, Stoppable stopper) {
       super("SplitLogManager Timeout Monitor", stopper, period);
     }
 
     @Override
     protected void chore() {
       int resubmitted = 0;
       int unassigned = 0;
       int tot = 0;
       boolean found_assigned_task = false;
       Set<ServerName> localDeadWorkers;
 
       synchronized (deadWorkersLock) {
         localDeadWorkers = deadWorkers;
         deadWorkers = null;
       }
 
       for (Map.Entry<String, Task> e : tasks.entrySet()) {
         String path = e.getKey();
         Task task = e.getValue();
         ServerName cur_worker = task.cur_worker_name;
         tot++;
         // don't easily resubmit a task which hasn't been picked up yet. It
         // might be a long while before a SplitLogWorker is free to pick up a
         // task. This is because a SplitLogWorker picks up a task one at a
         // time. If we want progress when there are no region servers then we
         // will have to run a SplitLogWorker thread in the Master.
         if (task.isUnassigned()) {
           unassigned++;
           continue;
         }
         found_assigned_task = true;
         if (localDeadWorkers != null && localDeadWorkers.contains(cur_worker)) {
           SplitLogCounters.tot_mgr_resubmit_dead_server_task.incrementAndGet();
           if (((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
               .getSplitLogManagerCoordination().resubmitTask(path, task, FORCE)) {
             resubmitted++;
           } else {
             handleDeadWorker(cur_worker);
             LOG.warn("Failed to resubmit task " + path + " owned by dead " + cur_worker
                 + ", will retry.");
           }
         } else if (((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
             .getSplitLogManagerCoordination().resubmitTask(path, task, CHECK)) {
           resubmitted++;
         }
       }
       if (tot > 0) {
         long now = EnvironmentEdgeManager.currentTime();
         if (now > lastLog + 5000) {
           lastLog = now;
           LOG.info("total tasks = " + tot + " unassigned = " + unassigned + " tasks=" + tasks);
         }
       }
       if (resubmitted > 0) {
         LOG.info("resubmitted " + resubmitted + " out of " + tot + " tasks");
       }
       // If there are pending tasks and all of them have been unassigned for
       // some time then put up a RESCAN node to ping the workers.
       // ZKSplitlog.DEFAULT_UNASSIGNED_TIMEOUT is of the order of minutes
       // because a. it is very unlikely that every worker had a
       // transient error when trying to grab the task b. if there are no
       // workers then all tasks wills stay unassigned indefinitely and the
       // manager will be indefinitely creating RESCAN nodes. TODO may be the
       // master should spawn both a manager and a worker thread to guarantee
       // that there is always one worker in the system
       if (tot > 0
           && !found_assigned_task
           && ((EnvironmentEdgeManager.currentTime() - lastTaskCreateTime) > unassignedTimeout)) {
         for (Map.Entry<String, Task> e : tasks.entrySet()) {
           String key = e.getKey();
           Task task = e.getValue();
           // we have to do task.isUnassigned() check again because tasks might
           // have been asynchronously assigned. There is no locking required
           // for these checks ... it is OK even if tryGetDataSetWatch() is
           // called unnecessarily for a taskpath
           if (task.isUnassigned() && (task.status != FAILURE)) {
             // We just touch the znode to make sure its still there
             ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
                 .getSplitLogManagerCoordination().checkTaskStillAvailable(key);
           }
         }
         ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
             .getSplitLogManagerCoordination().checkTasks();
         SplitLogCounters.tot_mgr_resubmit_unassigned.incrementAndGet();
         LOG.debug("resubmitting unassigned task(s) after timeout");
       }
       Set<String> failedDeletions =
           ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
               .getSplitLogManagerCoordination().getDetails().getFailedDeletions();
       // Retry previously failed deletes
       if (failedDeletions.size() > 0) {
         List<String> tmpPaths = new ArrayList<String>(failedDeletions);
         for (String tmpPath : tmpPaths) {
           // deleteNode is an async call
           ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
               .getSplitLogManagerCoordination().deleteTask(tmpPath);
         }
         failedDeletions.removeAll(tmpPaths);
       }
 
       // Garbage collect left-over
       long timeInterval =
           EnvironmentEdgeManager.currentTime()
               - ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
                   .getSplitLogManagerCoordination().getLastRecoveryTime();
       if (!failedRecoveringRegionDeletions.isEmpty()
           || (tot == 0 && tasks.size() == 0 && (timeInterval > checkRecoveringTimeThreshold))) {
         // inside the function there have more checks before GC anything
         if (!failedRecoveringRegionDeletions.isEmpty()) {
           List<Pair<Set<ServerName>, Boolean>> previouslyFailedDeletions =
               new ArrayList<Pair<Set<ServerName>, Boolean>>(failedRecoveringRegionDeletions);
           failedRecoveringRegionDeletions.removeAll(previouslyFailedDeletions);
           for (Pair<Set<ServerName>, Boolean> failedDeletion : previouslyFailedDeletions) {
             removeRecoveringRegions(failedDeletion.getFirst(), failedDeletion.getSecond());
           }
         } else {
           removeRecoveringRegions(null, null);
         }
       }
     }
   }
 
   public enum ResubmitDirective {
     CHECK(), FORCE();
   }
 
   public enum TerminationStatus {
     IN_PROGRESS("in_progress"), SUCCESS("success"), FAILURE("failure"), DELETED("deleted");
 
     String statusMsg;
 
     TerminationStatus(String msg) {
       statusMsg = msg;
     }
 
     @Override
     public String toString() {
       return statusMsg;
     }
   }
 }