/*
    *
    * 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.replication.regionserver;
  
  import java.io.EOFException;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Comparator;
  import java.util.List;
  import java.util.UUID;
  import java.util.concurrent.PriorityBlockingQueue;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.commons.lang.StringUtils;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  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.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.HBaseConfiguration;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.Stoppable;
  import org.apache.hadoop.hbase.wal.DefaultWALProvider;
  import org.apache.hadoop.hbase.wal.WAL;
  import org.apache.hadoop.hbase.wal.WALKey;
  import org.apache.hadoop.hbase.regionserver.wal.WALEdit;
  import org.apache.hadoop.hbase.replication.ChainWALEntryFilter;
  import org.apache.hadoop.hbase.replication.ReplicationEndpoint;
  import org.apache.hadoop.hbase.replication.ReplicationException;
  import org.apache.hadoop.hbase.replication.ReplicationPeers;
  import org.apache.hadoop.hbase.replication.ReplicationQueueInfo;
  import org.apache.hadoop.hbase.replication.ReplicationQueues;
  import org.apache.hadoop.hbase.replication.SystemTableWALEntryFilter;
  import org.apache.hadoop.hbase.replication.WALEntryFilter;
  import org.apache.hadoop.hbase.util.CancelableProgressable;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.util.FSUtils;
  import org.apache.hadoop.hbase.util.LeaseNotRecoveredException;
  import org.apache.hadoop.hbase.util.Threads;
  
  import com.google.common.collect.Lists;
  import com.google.common.util.concurrent.ListenableFuture;
  import com.google.common.util.concurrent.Service;
  
  /**
   * Class that handles the source of a replication stream.
   * Currently does not handle more than 1 slave
   * For each slave cluster it selects a random number of peers
   * using a replication ratio. For example, if replication ration = 0.1
   * and slave cluster has 100 region servers, 10 will be selected.
   * <p/>
   * A stream is considered down when we cannot contact a region server on the
   * peer cluster for more than 55 seconds by default.
   * <p/>
   *
   */
  @InterfaceAudience.Private
  public class ReplicationSource extends Thread
      implements ReplicationSourceInterface {
  
    public static final Log LOG = LogFactory.getLog(ReplicationSource.class);
    // Queue of logs to process
    private PriorityBlockingQueue<Path> queue;
    private ReplicationQueues replicationQueues;
    private ReplicationPeers replicationPeers;
  
    private Configuration conf;
    private ReplicationQueueInfo replicationQueueInfo;
    // id of the peer cluster this source replicates to
    private String peerId;
    // The manager of all sources to which we ping back our progress
    private ReplicationSourceManager manager;
    // Should we stop everything?
    private Stoppable stopper;
    // How long should we sleep for each retry
    private long sleepForRetries;
    // Max size in bytes of entriesArray
    private long replicationQueueSizeCapacity;
   // Max number of entries in entriesArray
   private int replicationQueueNbCapacity;
   // Our reader for the current log. open/close handled by repLogReader
   private WAL.Reader reader;
   // Last position in the log that we sent to ZooKeeper
   private long lastLoggedPosition = -1;
   // Path of the current log
   private volatile Path currentPath;
   private FileSystem fs;
   // id of this cluster
   private UUID clusterId;
   // id of the other cluster
   private UUID peerClusterId;
   // total number of edits we replicated
   private long totalReplicatedEdits = 0;
   // total number of edits we replicated
   private long totalReplicatedOperations = 0;
   // The znode we currently play with
   private String peerClusterZnode;
   // Maximum number of retries before taking bold actions
   private int maxRetriesMultiplier;
   // Current number of operations (Put/Delete) that we need to replicate
   private int currentNbOperations = 0;
   // Current size of data we need to replicate
   private int currentSize = 0;
   // Indicates if this particular source is running
   private volatile boolean running = true;
   // Metrics for this source
   private MetricsSource metrics;
   // Handle on the log reader helper
   private ReplicationWALReaderManager repLogReader;
   //WARN threshold for the number of queued logs, defaults to 2
   private int logQueueWarnThreshold;
   // ReplicationEndpoint which will handle the actual replication
   private ReplicationEndpoint replicationEndpoint;
   // A filter (or a chain of filters) for the WAL entries.
   private WALEntryFilter walEntryFilter;
   // throttler
   private ReplicationThrottler throttler;
 
   /**
    * Instantiation method used by region servers
    *
    * @param conf configuration to use
    * @param fs file system to use
    * @param manager replication manager to ping to
    * @param stopper     the atomic boolean to use to stop the regionserver
    * @param peerClusterZnode the name of our znode
    * @param clusterId unique UUID for the cluster
    * @param replicationEndpoint the replication endpoint implementation
    * @param metrics metrics for replication source
    * @throws IOException
    */
   @Override
   public void init(final Configuration conf, final FileSystem fs,
       final ReplicationSourceManager manager, final ReplicationQueues replicationQueues,
       final ReplicationPeers replicationPeers, final Stoppable stopper,
       final String peerClusterZnode, final UUID clusterId, ReplicationEndpoint replicationEndpoint,
       final MetricsSource metrics)
           throws IOException {
     this.stopper = stopper;
     this.conf = HBaseConfiguration.create(conf);
     decorateConf();
     this.replicationQueueSizeCapacity =
         this.conf.getLong("replication.source.size.capacity", 1024*1024*64);
     this.replicationQueueNbCapacity =
         this.conf.getInt("replication.source.nb.capacity", 25000);
     this.sleepForRetries =
         this.conf.getLong("replication.source.sleepforretries", 1000);    // 1 second
     this.maxRetriesMultiplier =
         this.conf.getInt("replication.source.maxretriesmultiplier", 300); // 5 minutes @ 1 sec per
     this.queue =
         new PriorityBlockingQueue<Path>(
             this.conf.getInt("hbase.regionserver.maxlogs", 32),
             new LogsComparator());
     long bandwidth = this.conf.getLong("replication.source.per.peer.node.bandwidth", 0);
     this.throttler = new ReplicationThrottler((double)bandwidth/10.0);
     this.replicationQueues = replicationQueues;
     this.replicationPeers = replicationPeers;
     this.manager = manager;
     this.fs = fs;
     this.metrics = metrics;
     this.repLogReader = new ReplicationWALReaderManager(this.fs, this.conf);
     this.clusterId = clusterId;
 
     this.peerClusterZnode = peerClusterZnode;
     this.replicationQueueInfo = new ReplicationQueueInfo(peerClusterZnode);
     // ReplicationQueueInfo parses the peerId out of the znode for us
     this.peerId = this.replicationQueueInfo.getPeerId();
     this.logQueueWarnThreshold = this.conf.getInt("replication.source.log.queue.warn", 2);
     this.replicationEndpoint = replicationEndpoint;
   }
 
   private void decorateConf() {
     String replicationCodec = this.conf.get(HConstants.REPLICATION_CODEC_CONF_KEY);
     if (StringUtils.isNotEmpty(replicationCodec)) {
       this.conf.set(HConstants.RPC_CODEC_CONF_KEY, replicationCodec);
     }
   }
 
   @Override
   public void enqueueLog(Path log) {
     this.queue.put(log);
     int queueSize = queue.size();
     this.metrics.setSizeOfLogQueue(queueSize);
     // This will log a warning for each new log that gets created above the warn threshold
     if (queueSize > this.logQueueWarnThreshold) {
       LOG.warn("Queue size: " + queueSize +
         " exceeds value of replication.source.log.queue.warn: " + logQueueWarnThreshold);
     }
   }
 
   private void uninitialize() {
     LOG.debug("Source exiting " + this.peerId);
     metrics.clear();
     if (replicationEndpoint.state() == Service.State.STARTING
         || replicationEndpoint.state() == Service.State.RUNNING) {
       replicationEndpoint.stopAndWait();
     }
   }
 
   @Override
   public void run() {
     // We were stopped while looping to connect to sinks, just abort
     if (!this.isActive()) {
       uninitialize();
       return;
     }
 
     try {
       // start the endpoint, connect to the cluster
       Service.State state = replicationEndpoint.start().get();
       if (state != Service.State.RUNNING) {
         LOG.warn("ReplicationEndpoint was not started. Exiting");
         uninitialize();
         return;
       }
     } catch (Exception ex) {
       LOG.warn("Error starting ReplicationEndpoint, exiting", ex);
       throw new RuntimeException(ex);
     }
 
     // get the WALEntryFilter from ReplicationEndpoint and add it to default filters
     ArrayList<WALEntryFilter> filters = Lists.newArrayList(
       (WALEntryFilter)new SystemTableWALEntryFilter());
     WALEntryFilter filterFromEndpoint = this.replicationEndpoint.getWALEntryfilter();
     if (filterFromEndpoint != null) {
       filters.add(filterFromEndpoint);
     }
     this.walEntryFilter = new ChainWALEntryFilter(filters);
 
     int sleepMultiplier = 1;
     // delay this until we are in an asynchronous thread
     while (this.isActive() && this.peerClusterId == null) {
       this.peerClusterId = replicationEndpoint.getPeerUUID();
       if (this.isActive() && this.peerClusterId == null) {
         if (sleepForRetries("Cannot contact the peer's zk ensemble", sleepMultiplier)) {
           sleepMultiplier++;
         }
       }
     }
     // We were stopped while looping to contact peer's zk ensemble, just abort
     if (!this.isActive()) {
       uninitialize();
       return;
     }
 
     // resetting to 1 to reuse later
     sleepMultiplier = 1;
 
     // In rare case, zookeeper setting may be messed up. That leads to the incorrect
     // peerClusterId value, which is the same as the source clusterId
     if (clusterId.equals(peerClusterId) && !replicationEndpoint.canReplicateToSameCluster()) {
       this.terminate("ClusterId " + clusterId + " is replicating to itself: peerClusterId "
           + peerClusterId + " which is not allowed by ReplicationEndpoint:"
           + replicationEndpoint.getClass().getName(), null, false);
     }
     LOG.info("Replicating "+clusterId + " -> " + peerClusterId);
 
     // If this is recovered, the queue is already full and the first log
     // normally has a position (unless the RS failed between 2 logs)
     if (this.replicationQueueInfo.isQueueRecovered()) {
       try {
         this.repLogReader.setPosition(this.replicationQueues.getLogPosition(this.peerClusterZnode,
           this.queue.peek().getName()));
         if (LOG.isTraceEnabled()) {
           LOG.trace("Recovered queue started with log " + this.queue.peek() +
               " at position " + this.repLogReader.getPosition());
         }
       } catch (ReplicationException e) {
         this.terminate("Couldn't get the position of this recovered queue " +
             this.peerClusterZnode, e);
       }
     }
     // Loop until we close down
     while (isActive()) {
       // Sleep until replication is enabled again
       if (!isPeerEnabled()) {
         if (sleepForRetries("Replication is disabled", sleepMultiplier)) {
           sleepMultiplier++;
         }
         continue;
       }
       Path oldPath = getCurrentPath(); //note that in the current scenario,
                                        //oldPath will be null when a log roll
                                        //happens.
       // Get a new path
       boolean hasCurrentPath = getNextPath();
       if (getCurrentPath() != null && oldPath == null) {
         sleepMultiplier = 1; //reset the sleepMultiplier on a path change
       }
       if (!hasCurrentPath) {
         if (sleepForRetries("No log to process", sleepMultiplier)) {
           sleepMultiplier++;
         }
         continue;
       }
       boolean currentWALisBeingWrittenTo = false;
       //For WAL files we own (rather than recovered), take a snapshot of whether the
       //current WAL file (this.currentPath) is in use (for writing) NOW!
       //Since the new WAL paths are enqueued only after the prev WAL file
       //is 'closed', presence of an element in the queue means that
       //the previous WAL file was closed, else the file is in use (currentPath)
       //We take the snapshot now so that we are protected against races
       //where a new file gets enqueued while the current file is being processed
       //(and where we just finished reading the current file).
       if (!this.replicationQueueInfo.isQueueRecovered() && queue.size() == 0) {
         currentWALisBeingWrittenTo = true;
       }
       // Open a reader on it
       if (!openReader(sleepMultiplier)) {
         // Reset the sleep multiplier, else it'd be reused for the next file
         sleepMultiplier = 1;
         continue;
       }
 
       // If we got a null reader but didn't continue, then sleep and continue
       if (this.reader == null) {
         if (sleepForRetries("Unable to open a reader", sleepMultiplier)) {
           sleepMultiplier++;
         }
         continue;
       }
 
       boolean gotIOE = false;
       currentNbOperations = 0;
       List<WAL.Entry> entries = new ArrayList<WAL.Entry>(1);
       currentSize = 0;
       try {
         if (readAllEntriesToReplicateOrNextFile(currentWALisBeingWrittenTo, entries)) {
           continue;
         }
       } catch (IOException ioe) {
         LOG.warn(this.peerClusterZnode + " Got: ", ioe);
         gotIOE = true;
         if (ioe.getCause() instanceof EOFException) {
 
           boolean considerDumping = false;
           if (this.replicationQueueInfo.isQueueRecovered()) {
             try {
               FileStatus stat = this.fs.getFileStatus(this.currentPath);
               if (stat.getLen() == 0) {
                 LOG.warn(this.peerClusterZnode + " Got EOF and the file was empty");
               }
               considerDumping = true;
             } catch (IOException e) {
               LOG.warn(this.peerClusterZnode + " Got while getting file size: ", e);
             }
           }
 
           if (considerDumping &&
               sleepMultiplier == this.maxRetriesMultiplier &&
               processEndOfFile()) {
             continue;
           }
         }
       } finally {
         try {
           this.reader = null;
           this.repLogReader.closeReader();
         } catch (IOException e) {
           gotIOE = true;
           LOG.warn("Unable to finalize the tailing of a file", e);
         }
       }
 
       // If we didn't get anything to replicate, or if we hit a IOE,
       // wait a bit and retry.
       // But if we need to stop, don't bother sleeping
       if (this.isActive() && (gotIOE || entries.isEmpty())) {
         if (this.lastLoggedPosition != this.repLogReader.getPosition()) {
           this.manager.logPositionAndCleanOldLogs(this.currentPath,
               this.peerClusterZnode, this.repLogReader.getPosition(),
               this.replicationQueueInfo.isQueueRecovered(), currentWALisBeingWrittenTo);
           this.lastLoggedPosition = this.repLogReader.getPosition();
         }
         // Reset the sleep multiplier if nothing has actually gone wrong
         if (!gotIOE) {
           sleepMultiplier = 1;
           // if there was nothing to ship and it's not an error
           // set "ageOfLastShippedOp" to <now> to indicate that we're current
           this.metrics.setAgeOfLastShippedOp(EnvironmentEdgeManager.currentTime());
         }
         if (sleepForRetries("Nothing to replicate", sleepMultiplier)) {
           sleepMultiplier++;
         }
         continue;
       }
       sleepMultiplier = 1;
       shipEdits(currentWALisBeingWrittenTo, entries);
     }
     uninitialize();
   }
 
   /**
    * Read all the entries from the current log files and retain those
    * that need to be replicated. Else, process the end of the current file.
    * @param currentWALisBeingWrittenTo is the current WAL being written to
    * @param entries resulting entries to be replicated
    * @return true if we got nothing and went to the next file, false if we got
    * entries
    * @throws IOException
    */
   protected boolean readAllEntriesToReplicateOrNextFile(boolean currentWALisBeingWrittenTo,
       List<WAL.Entry> entries) throws IOException {
     long seenEntries = 0;
     if (LOG.isTraceEnabled()) {
       LOG.trace("Seeking in " + this.currentPath + " at position "
           + this.repLogReader.getPosition());
     }
     this.repLogReader.seek();
     long positionBeforeRead = this.repLogReader.getPosition();
     WAL.Entry entry =
         this.repLogReader.readNextAndSetPosition();
     while (entry != null) {
       this.metrics.incrLogEditsRead();
       seenEntries++;
 
       // don't replicate if the log entries have already been consumed by the cluster
       if (replicationEndpoint.canReplicateToSameCluster()
           || !entry.getKey().getClusterIds().contains(peerClusterId)) {
         // Remove all KVs that should not be replicated
         entry = walEntryFilter.filter(entry);
         WALEdit edit = null;
         WALKey logKey = null;
         if (entry != null) {
           edit = entry.getEdit();
           logKey = entry.getKey();
         }
 
         if (edit != null && edit.size() != 0) {
           //Mark that the current cluster has the change
           logKey.addClusterId(clusterId);
           currentNbOperations += countDistinctRowKeys(edit);
           entries.add(entry);
           currentSize += entry.getEdit().heapSize();
         } else {
           this.metrics.incrLogEditsFiltered();
         }
       }
       // Stop if too many entries or too big
       if (currentSize >= this.replicationQueueSizeCapacity ||
           entries.size() >= this.replicationQueueNbCapacity) {
         break;
       }
       try {
         entry = this.repLogReader.readNextAndSetPosition();
       } catch (IOException ie) {
         LOG.debug("Break on IOE: " + ie.getMessage());
         break;
       }
     }
     metrics.incrLogReadInBytes(this.repLogReader.getPosition() - positionBeforeRead);
     if (currentWALisBeingWrittenTo) {
       return false;
     }
     // If we didn't get anything and the queue has an object, it means we
     // hit the end of the file for sure
     return seenEntries == 0 && processEndOfFile();
   }
 
   /**
    * Poll for the next path
    * @return true if a path was obtained, false if not
    */
   protected boolean getNextPath() {
     try {
       if (this.currentPath == null) {
         this.currentPath = queue.poll(this.sleepForRetries, TimeUnit.MILLISECONDS);
         this.metrics.setSizeOfLogQueue(queue.size());
         if (this.currentPath != null) {
           this.manager.cleanOldLogs(this.currentPath.getName(),
               this.peerId,
               this.replicationQueueInfo.isQueueRecovered());
           if (LOG.isTraceEnabled()) {
             LOG.trace("New log: " + this.currentPath);
           }
         }
       }
     } catch (InterruptedException e) {
       LOG.warn("Interrupted while reading edits", e);
     }
     return this.currentPath != null;
   }
 
   /**
    * Open a reader on the current path
    *
    * @param sleepMultiplier by how many times the default sleeping time is augmented
    * @return true if we should continue with that file, false if we are over with it
    */
   protected boolean openReader(int sleepMultiplier) {
     try {
       try {
         if (LOG.isTraceEnabled()) {
           LOG.trace("Opening log " + this.currentPath);
         }
         this.reader = repLogReader.openReader(this.currentPath);
       } catch (FileNotFoundException fnfe) {
         if (this.replicationQueueInfo.isQueueRecovered()) {
           // We didn't find the log in the archive directory, look if it still
           // exists in the dead RS folder (there could be a chain of failures
           // to look at)
           List<String> deadRegionServers = this.replicationQueueInfo.getDeadRegionServers();
           LOG.info("NB dead servers : " + deadRegionServers.size());
           final Path rootDir = FSUtils.getRootDir(this.conf);
           for (String curDeadServerName : deadRegionServers) {
             final Path deadRsDirectory = new Path(rootDir,
                 DefaultWALProvider.getWALDirectoryName(curDeadServerName));
             Path[] locs = new Path[] {
                 new Path(deadRsDirectory, currentPath.getName()),
                 new Path(deadRsDirectory.suffix(DefaultWALProvider.SPLITTING_EXT),
                                           currentPath.getName()),
             };
             for (Path possibleLogLocation : locs) {
               LOG.info("Possible location " + possibleLogLocation.toUri().toString());
               if (this.manager.getFs().exists(possibleLogLocation)) {
                 // We found the right new location
                 LOG.info("Log " + this.currentPath + " still exists at " +
                     possibleLogLocation);
                 // Breaking here will make us sleep since reader is null
                 // TODO why don't we need to set currentPath and call openReader here?
                 return true;
               }
             }
           }
           // In the case of disaster/recovery, HMaster may be shutdown/crashed before flush data
           // from .logs to .oldlogs. Loop into .logs folders and check whether a match exists
           if (stopper instanceof ReplicationSyncUp.DummyServer) {
             // N.B. the ReplicationSyncUp tool sets the manager.getLogDir to the root of the wal
             //      area rather than to the wal area for a particular region server.
             FileStatus[] rss = fs.listStatus(manager.getLogDir());
             for (FileStatus rs : rss) {
               Path p = rs.getPath();
               FileStatus[] logs = fs.listStatus(p);
               for (FileStatus log : logs) {
                 p = new Path(p, log.getPath().getName());
                 if (p.getName().equals(currentPath.getName())) {
                   currentPath = p;
                   LOG.info("Log " + currentPath.getName() + " found at " + currentPath);
                   // Open the log at the new location
                   this.openReader(sleepMultiplier);
                   return true;
                 }
               }
             }
           }
 
           // TODO What happens if the log was missing from every single location?
           // Although we need to check a couple of times as the log could have
           // been moved by the master between the checks
           // It can also happen if a recovered queue wasn't properly cleaned,
           // such that the znode pointing to a log exists but the log was
           // deleted a long time ago.
           // For the moment, we'll throw the IO and processEndOfFile
           throw new IOException("File from recovered queue is " +
               "nowhere to be found", fnfe);
         } else {
           // If the log was archived, continue reading from there
           Path archivedLogLocation =
               new Path(manager.getOldLogDir(), currentPath.getName());
           if (this.manager.getFs().exists(archivedLogLocation)) {
             currentPath = archivedLogLocation;
             LOG.info("Log " + this.currentPath + " was moved to " +
                 archivedLogLocation);
             // Open the log at the new location
             this.openReader(sleepMultiplier);
 
           }
           // TODO What happens the log is missing in both places?
         }
       }
     } catch (LeaseNotRecoveredException lnre) {
       // HBASE-15019 the WAL was not closed due to some hiccup.
       LOG.warn(peerClusterZnode + " Try to recover the WAL lease " + currentPath, lnre);
       recoverLease(conf, currentPath);
       this.reader = null;
     } catch (IOException ioe) {
       if (ioe instanceof EOFException && isCurrentLogEmpty()) return true;
       LOG.warn(this.peerClusterZnode + " Got: ", ioe);
       this.reader = null;
       if (ioe.getCause() instanceof NullPointerException) {
         // Workaround for race condition in HDFS-4380
         // which throws a NPE if we open a file before any data node has the most recent block
         // Just sleep and retry. Will require re-reading compressed WALs for compressionContext.
         LOG.warn("Got NPE opening reader, will retry.");
       } else if (sleepMultiplier == this.maxRetriesMultiplier) {
         // TODO Need a better way to determine if a file is really gone but
         // TODO without scanning all logs dir
         LOG.warn("Waited too long for this file, considering dumping");
         return !processEndOfFile();
       }
     }
     return true;
   }
 
   private void recoverLease(final Configuration conf, final Path path) {
     try {
       final FileSystem dfs = FSUtils.getCurrentFileSystem(conf);
       FSUtils fsUtils = FSUtils.getInstance(dfs, conf);
       fsUtils.recoverFileLease(dfs, path, conf, new CancelableProgressable() {
         @Override
         public boolean progress() {
           LOG.debug("recover WAL lease: " + path);
           return isActive();
         }
       });
     } catch (IOException e) {
       LOG.warn("unable to recover lease for WAL: " + path, e);
     }
   }
 
   /*
    * Checks whether the current log file is empty, and it is not a recovered queue. This is to
    * handle scenario when in an idle cluster, there is no entry in the current log and we keep on
    * trying to read the log file and get EOFException. In case of a recovered queue the last log
    * file may be empty, and we don't want to retry that.
    */
   private boolean isCurrentLogEmpty() {
     return (this.repLogReader.getPosition() == 0 &&
         !this.replicationQueueInfo.isQueueRecovered() && queue.size() == 0);
   }
 
   /**
    * Do the sleeping logic
    * @param msg Why we sleep
    * @param sleepMultiplier by how many times the default sleeping time is augmented
    * @return True if <code>sleepMultiplier</code> is &lt; <code>maxRetriesMultiplier</code>
    */
   protected boolean sleepForRetries(String msg, int sleepMultiplier) {
     try {
       if (LOG.isTraceEnabled()) {
         LOG.trace(msg + ", sleeping " + sleepForRetries + " times " + sleepMultiplier);
       }
       Thread.sleep(this.sleepForRetries * sleepMultiplier);
     } catch (InterruptedException e) {
       LOG.debug("Interrupted while sleeping between retries");
       Thread.currentThread().interrupt();
     }
     return sleepMultiplier < maxRetriesMultiplier;
   }
 
   /**
    * Count the number of different row keys in the given edit because of
    * mini-batching. We assume that there's at least one Cell in the WALEdit.
    * @param edit edit to count row keys from
    * @return number of different row keys
    */
   private int countDistinctRowKeys(WALEdit edit) {
     List<Cell> cells = edit.getCells();
     int distinctRowKeys = 1;
     Cell lastCell = cells.get(0);
     for (int i = 0; i < edit.size(); i++) {
       if (!CellUtil.matchingRow(cells.get(i), lastCell)) {
         distinctRowKeys++;
       }
       lastCell = cells.get(i);
     }
     return distinctRowKeys;
   }
 
   /**
    * Do the shipping logic
    * @param currentWALisBeingWrittenTo was the current WAL being (seemingly)
    * written to when this method was called
    */
   protected void shipEdits(boolean currentWALisBeingWrittenTo, List<WAL.Entry> entries) {
     int sleepMultiplier = 0;
     if (entries.isEmpty()) {
       LOG.warn("Was given 0 edits to ship");
       return;
     }
     while (this.isActive()) {
       try {
         if (this.throttler.isEnabled()) {
           long sleepTicks = this.throttler.getNextSleepInterval(currentSize);
           if (sleepTicks > 0) {
             try {
               if (LOG.isTraceEnabled()) {
                 LOG.trace("To sleep " + sleepTicks + "ms for throttling control");
               }
               Thread.sleep(sleepTicks);
             } catch (InterruptedException e) {
               LOG.debug("Interrupted while sleeping for throttling control");
               Thread.currentThread().interrupt();
               // current thread might be interrupted to terminate
               // directly go back to while() for confirm this
               continue;
             }
             // reset throttler's cycle start tick when sleep for throttling occurs
             this.throttler.resetStartTick();
           }
         }
         // create replicateContext here, so the entries can be GC'd upon return from this call stack
         ReplicationEndpoint.ReplicateContext replicateContext = new ReplicationEndpoint.ReplicateContext();
         replicateContext.setEntries(entries).setSize(currentSize);
 
         long startTimeNs = System.nanoTime();
         // send the edits to the endpoint. Will block until the edits are shipped and acknowledged
         boolean replicated = replicationEndpoint.replicate(replicateContext);
         long endTimeNs = System.nanoTime();
 
         if (!replicated) {
           continue;
         } else {
           sleepMultiplier = Math.max(sleepMultiplier-1, 0);
         }
 
         if (this.lastLoggedPosition != this.repLogReader.getPosition()) {
           this.manager.logPositionAndCleanOldLogs(this.currentPath,
               this.peerClusterZnode, this.repLogReader.getPosition(),
               this.replicationQueueInfo.isQueueRecovered(), currentWALisBeingWrittenTo);
           this.lastLoggedPosition = this.repLogReader.getPosition();
         }
         if (this.throttler.isEnabled()) {
           this.throttler.addPushSize(currentSize);
         }
         this.totalReplicatedEdits += entries.size();
         this.totalReplicatedOperations += currentNbOperations;
         this.metrics.shipBatch(this.currentNbOperations, this.currentSize/1024);
         this.metrics.setAgeOfLastShippedOp(entries.get(entries.size()-1).getKey().getWriteTime());
         if (LOG.isTraceEnabled()) {
           LOG.trace("Replicated " + this.totalReplicatedEdits + " entries in total, or "
               + this.totalReplicatedOperations + " operations in " +
               ((endTimeNs - startTimeNs)/1000000) + " ms");
         }
         break;
       } catch (Exception ex) {
         LOG.warn(replicationEndpoint.getClass().getName() + " threw unknown exception:" +
             org.apache.hadoop.util.StringUtils.stringifyException(ex));
         if (sleepForRetries("ReplicationEndpoint threw exception", sleepMultiplier)) {
           sleepMultiplier++;
         }
       }
     }
   }
 
   /**
    * check whether the peer is enabled or not
    *
    * @return true if the peer is enabled, otherwise false
    */
   protected boolean isPeerEnabled() {
     return this.replicationPeers.getStatusOfPeer(this.peerId);
   }
 
   /**
    * If the queue isn't empty, switch to the next one
    * Else if this is a recovered queue, it means we're done!
    * Else we'll just continue to try reading the log file
    * @return true if we're done with the current file, false if we should
    * continue trying to read from it
    */
   @edu.umd.cs.findbugs.annotations.SuppressWarnings(value="DE_MIGHT_IGNORE",
       justification="Yeah, this is how it works")
   protected boolean processEndOfFile() {
     // We presume this means the file we're reading is closed.
     if (this.queue.size() != 0) {
       // -1 means the wal wasn't closed cleanly.
       final long trailerSize = this.repLogReader.currentTrailerSize();
       final long currentPosition = this.repLogReader.getPosition();
       FileStatus stat = null;
       try {
         stat = fs.getFileStatus(this.currentPath);
       } catch (IOException exception) {
         LOG.warn("Couldn't get file length information about log " + this.currentPath + ", it " + (trailerSize < 0 ? "was not" : "was") + " closed cleanly"
             + ", stats: " + getStats());
         metrics.incrUnknownFileLengthForClosedWAL();
       }
       if (stat != null) {
         if (trailerSize < 0) {
           if (currentPosition < stat.getLen()) {
             final long skippedBytes = stat.getLen() - currentPosition;
             LOG.info("Reached the end of WAL file '" + currentPath + "'. It was not closed cleanly, so we did not parse " + skippedBytes + " bytes of data.");
             metrics.incrUncleanlyClosedWALs();
             metrics.incrBytesSkippedInUncleanlyClosedWALs(skippedBytes);
           }
         } else if (currentPosition + trailerSize < stat.getLen()){
           LOG.warn("Processing end of WAL file '" + currentPath + "'. At position " + currentPosition + ", which is too far away from reported file length " + stat.getLen() +
             ". Restarting WAL reading (see HBASE-15983 for details). stats: " + getStats());
           repLogReader.setPosition(0);
           metrics.incrRestartedWALReading();
           metrics.incrRepeatedFileBytes(currentPosition);
           return false;
         }
       }
       if (LOG.isTraceEnabled()) {
         LOG.trace("Reached the end of a log, stats: " + getStats()
           + ", and the length of the file is " + (stat == null ? "N/A" : stat.getLen()));
       }
       this.currentPath = null;
       this.repLogReader.finishCurrentFile();
       this.reader = null;
       metrics.incrCompletedWAL();
       return true;
     } else if (this.replicationQueueInfo.isQueueRecovered()) {
       this.manager.closeRecoveredQueue(this);
       LOG.info("Finished recovering the queue with the following stats " + getStats());
       metrics.incrCompletedRecoveryQueue();
       this.running = false;
       return true;
     }
     return false;
   }
 
   @Override
   public void startup() {
     String n = Thread.currentThread().getName();
     Thread.UncaughtExceptionHandler handler =
         new Thread.UncaughtExceptionHandler() {
           @Override
           public void uncaughtException(final Thread t, final Throwable e) {
             LOG.error("Unexpected exception in ReplicationSource," +
               " currentPath=" + currentPath, e);
           }
         };
     Threads.setDaemonThreadRunning(
         this, n + ".replicationSource," +
         this.peerClusterZnode, handler);
   }
 
   @Override
   public void terminate(String reason) {
     terminate(reason, null);
   }
 
   @Override
   public void terminate(String reason, Exception cause) {
     terminate(reason, cause, true);
   }
 
   public void terminate(String reason, Exception cause, boolean join) {
     if (cause == null) {
       LOG.info("Closing source "
           + this.peerClusterZnode + " because: " + reason);
 
     } else {
       LOG.error("Closing source " + this.peerClusterZnode
           + " because an error occurred: " + reason, cause);
     }
     this.running = false;
     this.interrupt();
     ListenableFuture<Service.State> future = null;
     if (this.replicationEndpoint != null) {
       future = this.replicationEndpoint.stop();
     }
     if (join) {
       Threads.shutdown(this, this.sleepForRetries);
       if (future != null) {
         try {
           future.get();
         } catch (Exception e) {
           LOG.warn("Got exception:" + e);
         }
       }
     }
   }
 
   @Override
   public String getPeerClusterZnode() {
     return this.peerClusterZnode;
   }
 
   @Override
   public String getPeerClusterId() {
     return this.peerId;
   }
 
   @Override
   public Path getCurrentPath() {
     return this.currentPath;
   }
 
   private boolean isActive() {
     return !this.stopper.isStopped() && this.running && !isInterrupted();
   }
 
   /**
    * Comparator used to compare logs together based on their start time
    */
   public static class LogsComparator implements Comparator<Path> {
 
     @Override
     public int compare(Path o1, Path o2) {
       return Long.valueOf(getTS(o1)).compareTo(getTS(o2));
     }
 
     /**
      * Split a path to get the start time
      * For example: 10.20.20.171%3A60020.1277499063250
      * @param p path to split
      * @return start time
      */
     private static long getTS(Path p) {
       int tsIndex = p.getName().lastIndexOf('.') + 1;
       return Long.parseLong(p.getName().substring(tsIndex));
     }
   }
 
   @Override
   public String getStats() {
     long position = this.repLogReader.getPosition();
     return "Total replicated edits: " + totalReplicatedEdits +
       ", currently replicating from: " + this.currentPath +
       " at position: " + position;
   }
 
   /**
    * Get Replication Source Metrics
    * @return sourceMetrics
    */
   public MetricsSource getSourceMetrics() {
     return this.metrics;
   }
 }