/**
    *
    * 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.regionserver.wal;
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.net.URLEncoder;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.SortedMap;
  import java.util.TreeMap;
  import java.util.TreeSet;
  import java.util.UUID;
  import java.util.concurrent.ConcurrentSkipListMap;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FSDataOutputStream;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.fs.Syncable;
  import org.apache.hadoop.hbase.HBaseConfiguration;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.exceptions.FailedLogCloseException;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.ClassSize;
  import org.apache.hadoop.hbase.util.DrainBarrier;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.util.FSUtils;
  import org.apache.hadoop.hbase.util.HasThread;
  import org.apache.hadoop.hbase.util.Threads;
  import org.apache.hadoop.util.StringUtils;
  
  /**
   * HLog stores all the edits to the HStore.  Its the hbase write-ahead-log
   * implementation.
   *
   * It performs logfile-rolling, so external callers are not aware that the
   * underlying file is being rolled.
   *
   * <p>
   * There is one HLog per RegionServer.  All edits for all Regions carried by
   * a particular RegionServer are entered first in the HLog.
   *
   * <p>
   * Each HRegion is identified by a unique long <code>int</code>. HRegions do
   * not need to declare themselves before using the HLog; they simply include
   * their HRegion-id in the <code>append</code> or
   * <code>completeCacheFlush</code> calls.
   *
   * <p>
   * An HLog consists of multiple on-disk files, which have a chronological order.
   * As data is flushed to other (better) on-disk structures, the log becomes
   * obsolete. We can destroy all the log messages for a given HRegion-id up to
   * the most-recent CACHEFLUSH message from that HRegion.
   *
   * <p>
   * It's only practical to delete entire files. Thus, we delete an entire on-disk
   * file F when all of the messages in F have a log-sequence-id that's older
   * (smaller) than the most-recent CACHEFLUSH message for every HRegion that has
   * a message in F.
   *
   * <p>
   * Synchronized methods can never execute in parallel. However, between the
   * start of a cache flush and the completion point, appends are allowed but log
   * rolling is not. To prevent log rolling taking place during this period, a
  * separate reentrant lock is used.
  *
  * <p>To read an HLog, call {@link HLogFactory#createReader(org.apache.hadoop.fs.FileSystem,
  * org.apache.hadoop.fs.Path, org.apache.hadoop.conf.Configuration)}.
  *
  */
 @InterfaceAudience.Private
 class FSHLog implements HLog, Syncable {
   static final Log LOG = LogFactory.getLog(FSHLog.class);
 
   private final FileSystem fs;
   private final Path rootDir;
   private final Path dir;
   private final Configuration conf;
   // Listeners that are called on WAL events.
   private List<WALActionsListener> listeners =
     new CopyOnWriteArrayList<WALActionsListener>();
   private final long optionalFlushInterval;
   private final long blocksize;
   private final String prefix;
   private final AtomicLong unflushedEntries = new AtomicLong(0);
   private volatile long syncedTillHere = 0;
   private long lastDeferredTxid;
   private final Path oldLogDir;
   private volatile boolean logRollRunning;
 
   private WALCoprocessorHost coprocessorHost;
 
   private FSDataOutputStream hdfs_out; // FSDataOutputStream associated with the current SequenceFile.writer
   // Minimum tolerable replicas, if the actual value is lower than it,
   // rollWriter will be triggered
   private int minTolerableReplication;
   private Method getNumCurrentReplicas; // refers to DFSOutputStream.getNumCurrentReplicas
   final static Object [] NO_ARGS = new Object []{};
 
   /** The barrier used to ensure that close() waits for all log rolls and flushes to finish. */
   private DrainBarrier closeBarrier = new DrainBarrier();
 
   /**
    * Current log file.
    */
   Writer writer;
 
   /**
    * Map of all log files but the current one.
    */
   final SortedMap<Long, Path> outputfiles =
     Collections.synchronizedSortedMap(new TreeMap<Long, Path>());
 
 
   /**
    * This lock synchronizes all operations on oldestUnflushedSeqNums and oldestFlushingSeqNums,
    * with the exception of append's putIfAbsent into oldestUnflushedSeqNums.
    * We only use these to find out the low bound seqNum, or to find regions with old seqNums to
    * force flush them, so we don't care about these numbers messing with anything. */
   private final Object oldestSeqNumsLock = new Object();
 
   /**
    * This lock makes sure only one log roll runs at the same time. Should not be taken while
    * any other lock is held. We don't just use synchronized because that results in bogus and
    * tedious findbugs warning when it thinks synchronized controls writer thread safety */
   private final Object rollWriterLock = new Object();
 
   /**
    * Map of encoded region names to their most recent sequence/edit id in their memstore.
    */
   private final ConcurrentSkipListMap<byte [], Long> oldestUnflushedSeqNums =
     new ConcurrentSkipListMap<byte [], Long>(Bytes.BYTES_COMPARATOR);
   /**
    * Map of encoded region names to their most recent sequence/edit id in their memstore;
    * contains the regions that are currently flushing. That way we can store two numbers for
    * flushing and non-flushing (oldestUnflushedSeqNums) memstore for the same region.
    */
   private final Map<byte[], Long> oldestFlushingSeqNums =
     new TreeMap<byte[], Long>(Bytes.BYTES_COMPARATOR);
 
   private volatile boolean closed = false;
 
   private final AtomicLong logSeqNum = new AtomicLong(0);
 
   private boolean forMeta = false;
 
   // The timestamp (in ms) when the log file was created.
   private volatile long filenum = -1;
 
   //number of transactions in the current Hlog.
   private final AtomicInteger numEntries = new AtomicInteger(0);
 
   // If live datanode count is lower than the default replicas value,
   // RollWriter will be triggered in each sync(So the RollWriter will be
   // triggered one by one in a short time). Using it as a workaround to slow
   // down the roll frequency triggered by checkLowReplication().
   private AtomicInteger consecutiveLogRolls = new AtomicInteger(0);
   private final int lowReplicationRollLimit;
 
   // If consecutiveLogRolls is larger than lowReplicationRollLimit,
   // then disable the rolling in checkLowReplication().
   // Enable it if the replications recover.
   private volatile boolean lowReplicationRollEnabled = true;
 
   // If > than this size, roll the log. This is typically 0.95 times the size
   // of the default Hdfs block size.
   private final long logrollsize;
 
   // We synchronize on updateLock to prevent updates and to prevent a log roll
   // during an update
   // locked during appends
   private final Object updateLock = new Object();
   private final Object flushLock = new Object();
 
   private final boolean enabled;
 
   /*
    * If more than this many logs, force flush of oldest region to oldest edit
    * goes to disk.  If too many and we crash, then will take forever replaying.
    * Keep the number of logs tidy.
    */
   private final int maxLogs;
 
   /**
    * Thread that handles optional sync'ing
    */
   private final LogSyncer logSyncer;
 
   /** Number of log close errors tolerated before we abort */
   private final int closeErrorsTolerated;
 
   private final AtomicInteger closeErrorCount = new AtomicInteger();
   private final MetricsWAL metrics;
 
   /**
    * Constructor.
    *
    * @param fs filesystem handle
    * @param root path for stored and archived hlogs
    * @param logDir dir where hlogs are stored
    * @param conf configuration to use
    * @throws IOException
    */
   public FSHLog(final FileSystem fs, final Path root, final String logDir,
                 final Configuration conf)
   throws IOException {
     this(fs, root, logDir, HConstants.HREGION_OLDLOGDIR_NAME,
         conf, null, true, null, false);
   }
 
   /**
    * Constructor.
    *
    * @param fs filesystem handle
    * @param root path for stored and archived hlogs
    * @param logDir dir where hlogs are stored
    * @param oldLogDir dir where hlogs are archived
    * @param conf configuration to use
    * @throws IOException
    */
   public FSHLog(final FileSystem fs, final Path root, final String logDir,
                 final String oldLogDir, final Configuration conf)
   throws IOException {
     this(fs, root, logDir, oldLogDir,
         conf, null, true, null, false);
   }
 
   /**
    * Create an edit log at the given <code>dir</code> location.
    *
    * You should never have to load an existing log. If there is a log at
    * startup, it should have already been processed and deleted by the time the
    * HLog object is started up.
    *
    * @param fs filesystem handle
    * @param root path for stored and archived hlogs
    * @param logDir dir where hlogs are stored
    * @param conf configuration to use
    * @param listeners Listeners on WAL events. Listeners passed here will
    * be registered before we do anything else; e.g. the
    * Constructor {@link #rollWriter()}.
    * @param prefix should always be hostname and port in distributed env and
    *        it will be URL encoded before being used.
    *        If prefix is null, "hlog" will be used
    * @throws IOException
    */
   public FSHLog(final FileSystem fs, final Path root, final String logDir,
       final Configuration conf, final List<WALActionsListener> listeners,
       final String prefix) throws IOException {
     this(fs, root, logDir, HConstants.HREGION_OLDLOGDIR_NAME,
         conf, listeners, true, prefix, false);
   }
 
   /**
    * Create an edit log at the given <code>dir</code> location.
    *
    * You should never have to load an existing log. If there is a log at
    * startup, it should have already been processed and deleted by the time the
    * HLog object is started up.
    *
    * @param fs filesystem handle
    * @param root path to where logs and oldlogs
    * @param logDir dir where hlogs are stored
    * @param oldLogDir dir where hlogs are archived
    * @param conf configuration to use
    * @param listeners Listeners on WAL events. Listeners passed here will
    * be registered before we do anything else; e.g. the
    * Constructor {@link #rollWriter()}.
    * @param failIfLogDirExists If true IOException will be thrown if dir already exists.
    * @param prefix should always be hostname and port in distributed env and
    *        it will be URL encoded before being used.
    *        If prefix is null, "hlog" will be used
    * @param forMeta if this hlog is meant for meta updates
    * @throws IOException
    */
   public FSHLog(final FileSystem fs, final Path root, final String logDir,
       final String oldLogDir, final Configuration conf,
       final List<WALActionsListener> listeners,
       final boolean failIfLogDirExists, final String prefix, boolean forMeta)
   throws IOException {
     super();
     this.fs = fs;
     this.rootDir = root;
     this.dir = new Path(this.rootDir, logDir);
     this.oldLogDir = new Path(this.rootDir, oldLogDir);
     this.forMeta = forMeta;
     this.conf = conf;
 
     if (listeners != null) {
       for (WALActionsListener i: listeners) {
         registerWALActionsListener(i);
       }
     }
 
     this.blocksize = this.conf.getLong("hbase.regionserver.hlog.blocksize",
         FSUtils.getDefaultBlockSize(this.fs, this.dir));
     // Roll at 95% of block size.
     float multi = conf.getFloat("hbase.regionserver.logroll.multiplier", 0.95f);
     this.logrollsize = (long)(this.blocksize * multi);
     this.optionalFlushInterval =
       conf.getLong("hbase.regionserver.optionallogflushinterval", 1 * 1000);
 
     this.maxLogs = conf.getInt("hbase.regionserver.maxlogs", 32);
     this.minTolerableReplication = conf.getInt(
         "hbase.regionserver.hlog.tolerable.lowreplication",
         FSUtils.getDefaultReplication(fs, this.dir));
     this.lowReplicationRollLimit = conf.getInt(
         "hbase.regionserver.hlog.lowreplication.rolllimit", 5);
     this.enabled = conf.getBoolean("hbase.regionserver.hlog.enabled", true);
     this.closeErrorsTolerated = conf.getInt(
         "hbase.regionserver.logroll.errors.tolerated", 0);
 
     this.logSyncer = new LogSyncer(this.optionalFlushInterval);
 
     LOG.info("WAL/HLog configuration: blocksize=" +
       StringUtils.byteDesc(this.blocksize) +
       ", rollsize=" + StringUtils.byteDesc(this.logrollsize) +
       ", enabled=" + this.enabled +
       ", optionallogflushinternal=" + this.optionalFlushInterval + "ms");
     // If prefix is null||empty then just name it hlog
     this.prefix = prefix == null || prefix.isEmpty() ?
         "hlog" : URLEncoder.encode(prefix, "UTF8");
 
     boolean dirExists = false;
     if (failIfLogDirExists && (dirExists = this.fs.exists(dir))) {
       throw new IOException("Target HLog directory already exists: " + dir);
     }
     if (!dirExists && !fs.mkdirs(dir)) {
       throw new IOException("Unable to mkdir " + dir);
     }
 
     if (!fs.exists(this.oldLogDir)) {
       if (!fs.mkdirs(this.oldLogDir)) {
         throw new IOException("Unable to mkdir " + this.oldLogDir);
       }
     }
     // rollWriter sets this.hdfs_out if it can.
     rollWriter();
 
     // handle the reflection necessary to call getNumCurrentReplicas()
     this.getNumCurrentReplicas = getGetNumCurrentReplicas(this.hdfs_out);
 
     // When optionalFlushInterval is set as 0, don't start a thread for deferred log sync.
     if (this.optionalFlushInterval > 0) {
       Threads.setDaemonThreadRunning(logSyncer.getThread(), Thread.currentThread().getName()
           + ".logSyncer");
     } else {
       LOG.info("hbase.regionserver.optionallogflushinterval is set as "
           + this.optionalFlushInterval + ". Deferred log syncing won't work. "
           + "Any Mutation, marked to be deferred synced, will be flushed immediately.");
     }
     coprocessorHost = new WALCoprocessorHost(this, conf);
 
     this.metrics = new MetricsWAL();
   }
 
   /**
    * Find the 'getNumCurrentReplicas' on the passed <code>os</code> stream.
    * @return Method or null.
    */
   private Method getGetNumCurrentReplicas(final FSDataOutputStream os) {
     Method m = null;
     if (os != null) {
       Class<? extends OutputStream> wrappedStreamClass = os.getWrappedStream()
           .getClass();
       try {
         m = wrappedStreamClass.getDeclaredMethod("getNumCurrentReplicas",
             new Class<?>[] {});
         m.setAccessible(true);
       } catch (NoSuchMethodException e) {
         LOG.info("FileSystem's output stream doesn't support"
             + " getNumCurrentReplicas; --HDFS-826 not available; fsOut="
             + wrappedStreamClass.getName());
       } catch (SecurityException e) {
         LOG.info("Doesn't have access to getNumCurrentReplicas on "
             + "FileSystems's output stream --HDFS-826 not available; fsOut="
             + wrappedStreamClass.getName(), e);
         m = null; // could happen on setAccessible()
       }
     }
     if (m != null) {
       if (LOG.isTraceEnabled()) LOG.trace("Using getNumCurrentReplicas--HDFS-826");
     }
     return m;
   }
 
   @Override
   public void registerWALActionsListener(final WALActionsListener listener) {
     this.listeners.add(listener);
   }
 
   @Override
   public boolean unregisterWALActionsListener(final WALActionsListener listener) {
     return this.listeners.remove(listener);
   }
 
   @Override
   public long getFilenum() {
     return this.filenum;
   }
 
   @Override
   public void setSequenceNumber(final long newvalue) {
     for (long id = this.logSeqNum.get(); id < newvalue &&
         !this.logSeqNum.compareAndSet(id, newvalue); id = this.logSeqNum.get()) {
       // This could spin on occasion but better the occasional spin than locking
       // every increment of sequence number.
       LOG.debug("Changed sequenceid from " + id + " to " + newvalue);
     }
   }
 
   @Override
   public long getSequenceNumber() {
     return logSeqNum.get();
   }
 
   /**
    * Method used internal to this class and for tests only.
    * @return The wrapped stream our writer is using; its not the
    * writer's 'out' FSDatoOutputStream but the stream that this 'out' wraps
    * (In hdfs its an instance of DFSDataOutputStream).
    *
    * usage: see TestLogRolling.java
    */
   OutputStream getOutputStream() {
     return this.hdfs_out.getWrappedStream();
   }
 
   @Override
   public byte [][] rollWriter() throws FailedLogCloseException, IOException {
     return rollWriter(false);
   }
 
   @Override
   public byte [][] rollWriter(boolean force)
       throws FailedLogCloseException, IOException {
     synchronized (rollWriterLock) {
       // Return if nothing to flush.
       if (!force && this.writer != null && this.numEntries.get() <= 0) {
         return null;
       }
       byte [][] regionsToFlush = null;
       if (closed) {
         LOG.debug("HLog closed. Skipping rolling of writer");
         return null;
       }
       try {
         this.logRollRunning = true;
         if (!closeBarrier.beginOp()) {
           LOG.debug("HLog closing. Skipping rolling of writer");
           return regionsToFlush;
         }
         // Do all the preparation outside of the updateLock to block
         // as less as possible the incoming writes
         long currentFilenum = this.filenum;
         Path oldPath = null;
         if (currentFilenum > 0) {
           //computeFilename  will take care of meta hlog filename
           oldPath = computeFilename(currentFilenum);
         }
         this.filenum = System.currentTimeMillis();
         Path newPath = computeFilename();
 
         // Tell our listeners that a new log is about to be created
         if (!this.listeners.isEmpty()) {
           for (WALActionsListener i : this.listeners) {
             i.preLogRoll(oldPath, newPath);
           }
         }
         FSHLog.Writer nextWriter = this.createWriterInstance(fs, newPath, conf);
         // Can we get at the dfsclient outputstream?
         FSDataOutputStream nextHdfsOut = null;
         if (nextWriter instanceof ProtobufLogWriter) {
           nextHdfsOut = ((ProtobufLogWriter)nextWriter).getStream();
         }
 
         Path oldFile = null;
         int oldNumEntries = 0;
         synchronized (updateLock) {
           // Clean up current writer.
           oldNumEntries = this.numEntries.get();
           oldFile = cleanupCurrentWriter(currentFilenum);
           this.writer = nextWriter;
           this.hdfs_out = nextHdfsOut;
           this.numEntries.set(0);
         }
         if (oldFile == null) LOG.info("New WAL " + FSUtils.getPath(newPath));
         else LOG.info("Rolled WAL " + FSUtils.getPath(oldFile) + " with entries=" + oldNumEntries +
           ", filesize=" + StringUtils.humanReadableInt(this.fs.getFileStatus(oldFile).getLen()) +
           "; new WAL " + FSUtils.getPath(newPath));
 
         // Tell our listeners that a new log was created
         if (!this.listeners.isEmpty()) {
           for (WALActionsListener i : this.listeners) {
             i.postLogRoll(oldPath, newPath);
           }
         }
 
         // Can we delete any of the old log files?
         if (getNumLogFiles() > 0) {
           cleanOldLogs();
           regionsToFlush = getRegionsToForceFlush();
         }
       } finally {
         this.logRollRunning = false;
         closeBarrier.endOp();
       }
       return regionsToFlush;
     }
   }
 
   /**
    * This method allows subclasses to inject different writers without having to
    * extend other methods like rollWriter().
    *
    * @param fs
    * @param path
    * @param conf
    * @return Writer instance
    * @throws IOException
    */
   protected Writer createWriterInstance(final FileSystem fs, final Path path,
       final Configuration conf) throws IOException {
     if (forMeta) {
       //TODO: set a higher replication for the hlog files (HBASE-6773)
     }
     return HLogFactory.createWriter(fs, path, conf);
   }
 
   /*
    * Clean up old commit logs.
    * @return If lots of logs, flush the returned region so next time through
    * we can clean logs. Returns null if nothing to flush.  Returns array of
    * encoded region names to flush.
    * @throws IOException
    */
   private void cleanOldLogs() throws IOException {
     long oldestOutstandingSeqNum = Long.MAX_VALUE;
     synchronized (oldestSeqNumsLock) {
       Long oldestFlushing = (oldestFlushingSeqNums.size() > 0)
         ? Collections.min(oldestFlushingSeqNums.values()) : Long.MAX_VALUE;
       Long oldestUnflushed = (oldestUnflushedSeqNums.size() > 0)
         ? Collections.min(oldestUnflushedSeqNums.values()) : Long.MAX_VALUE;
       oldestOutstandingSeqNum = Math.min(oldestFlushing, oldestUnflushed);
     }
 
     // Get the set of all log files whose last sequence number is smaller than
     // the oldest edit's sequence number.
     TreeSet<Long> sequenceNumbers = new TreeSet<Long>(this.outputfiles.headMap(
         oldestOutstandingSeqNum).keySet());
     // Now remove old log files (if any)
     if (LOG.isDebugEnabled()) {
       if (sequenceNumbers.size() > 0) {
         LOG.debug("Found " + sequenceNumbers.size() + " hlogs to remove" +
           " out of total " + this.outputfiles.size() + ";" +
           " oldest outstanding sequenceid is " + oldestOutstandingSeqNum);
       }
     }
     for (Long seq : sequenceNumbers) {
       archiveLogFile(this.outputfiles.remove(seq), seq);
     }
   }
 
   /**
    * Return regions that have edits that are equal or less than a certain sequence number.
    * Static due to some old unit test.
    * @param walSeqNum The sequence number to compare with.
    * @param regionsToSeqNums Encoded region names to sequence ids
    * @return All regions whose seqNum <= walSeqNum. Null if no regions found.
    */
   static byte[][] findMemstoresWithEditsEqualOrOlderThan(
       final long walSeqNum, final Map<byte[], Long> regionsToSeqNums) {
     List<byte[]> regions = null;
     for (Map.Entry<byte[], Long> e : regionsToSeqNums.entrySet()) {
       if (e.getValue().longValue() <= walSeqNum) {
         if (regions == null) regions = new ArrayList<byte[]>();
         regions.add(e.getKey());
       }
     }
     return regions == null ? null : regions
         .toArray(new byte[][] { HConstants.EMPTY_BYTE_ARRAY });
   }
 
   private byte[][] getRegionsToForceFlush() throws IOException {
     // If too many log files, figure which regions we need to flush.
     // Array is an array of encoded region names.
     byte [][] regions = null;
     int logCount = getNumLogFiles();
     if (logCount > this.maxLogs && logCount > 0) {
       // This is an array of encoded region names.
       synchronized (oldestSeqNumsLock) {
         regions = findMemstoresWithEditsEqualOrOlderThan(this.outputfiles.firstKey(),
           this.oldestUnflushedSeqNums);
       }
       if (regions != null) {
         StringBuilder sb = new StringBuilder();
         for (int i = 0; i < regions.length; i++) {
           if (i > 0) sb.append(", ");
           sb.append(Bytes.toStringBinary(regions[i]));
         }
         LOG.info("Too many hlogs: logs=" + logCount + ", maxlogs=" +
            this.maxLogs + "; forcing flush of " + regions.length + " regions(s): " +
            sb.toString());
       }
     }
     return regions;
   }
 
   /*
    * Cleans up current writer closing and adding to outputfiles.
    * Presumes we're operating inside an updateLock scope.
    * @return Path to current writer or null if none.
    * @throws IOException
    */
   Path cleanupCurrentWriter(final long currentfilenum) throws IOException {
     Path oldFile = null;
     if (this.writer != null) {
       // Close the current writer, get a new one.
       try {
         // Wait till all current transactions are written to the hlog.
         // No new transactions can occur because we have the updatelock.
         if (this.unflushedEntries.get() != this.syncedTillHere) {
           LOG.debug("cleanupCurrentWriter " +
                    " waiting for transactions to get synced " +
                    " total " + this.unflushedEntries.get() +
                    " synced till here " + syncedTillHere);
           sync();
         }
         this.writer.close();
         this.writer = null;
         closeErrorCount.set(0);
       } catch (IOException e) {
         LOG.error("Failed close of HLog writer", e);
         int errors = closeErrorCount.incrementAndGet();
         if (errors <= closeErrorsTolerated && !hasDeferredEntries()) {
           LOG.warn("Riding over HLog close failure! error count="+errors);
         } else {
           if (hasDeferredEntries()) {
             LOG.error("Aborting due to unflushed edits in HLog");
           }
           // Failed close of log file.  Means we're losing edits.  For now,
           // shut ourselves down to minimize loss.  Alternative is to try and
           // keep going.  See HBASE-930.
           FailedLogCloseException flce =
             new FailedLogCloseException("#" + currentfilenum);
           flce.initCause(e);
           throw flce;
         }
       }
       if (currentfilenum >= 0) {
         oldFile = computeFilename(currentfilenum);
         this.outputfiles.put(Long.valueOf(this.logSeqNum.get()), oldFile);
       }
     }
     return oldFile;
   }
 
   private void archiveLogFile(final Path p, final Long seqno) throws IOException {
     Path newPath = getHLogArchivePath(this.oldLogDir, p);
     LOG.info("moving old hlog file " + FSUtils.getPath(p) +
       " whose highest sequenceid is " + seqno + " to " +
       FSUtils.getPath(newPath));
 
     // Tell our listeners that a log is going to be archived.
     if (!this.listeners.isEmpty()) {
       for (WALActionsListener i : this.listeners) {
         i.preLogArchive(p, newPath);
       }
     }
     if (!FSUtils.renameAndSetModifyTime(this.fs, p, newPath)) {
       throw new IOException("Unable to rename " + p + " to " + newPath);
     }
     // Tell our listeners that a log has been archived.
     if (!this.listeners.isEmpty()) {
       for (WALActionsListener i : this.listeners) {
         i.postLogArchive(p, newPath);
       }
     }
   }
 
   /**
    * This is a convenience method that computes a new filename with a given
    * using the current HLog file-number
    * @return Path
    */
   protected Path computeFilename() {
     return computeFilename(this.filenum);
   }
 
   /**
    * This is a convenience method that computes a new filename with a given
    * file-number.
    * @param filenum to use
    * @return Path
    */
   protected Path computeFilename(long filenum) {
     if (filenum < 0) {
       throw new RuntimeException("hlog file number can't be < 0");
     }
     String child = prefix + "." + filenum;
     if (forMeta) {
       child += HLog.META_HLOG_FILE_EXTN;
     }
     return new Path(dir, child);
   }
 
   @Override
   public void closeAndDelete() throws IOException {
     close();
     if (!fs.exists(this.dir)) return;
     FileStatus[] files = fs.listStatus(this.dir);
     if (files != null) {
       for(FileStatus file : files) {
 
         Path p = getHLogArchivePath(this.oldLogDir, file.getPath());
         // Tell our listeners that a log is going to be archived.
         if (!this.listeners.isEmpty()) {
           for (WALActionsListener i : this.listeners) {
             i.preLogArchive(file.getPath(), p);
           }
         }
 
         if (!FSUtils.renameAndSetModifyTime(fs, file.getPath(), p)) {
           throw new IOException("Unable to rename " + file.getPath() + " to " + p);
         }
         // Tell our listeners that a log was archived.
         if (!this.listeners.isEmpty()) {
           for (WALActionsListener i : this.listeners) {
             i.postLogArchive(file.getPath(), p);
           }
         }
       }
       LOG.debug("Moved " + files.length + " WAL file(s) to " + FSUtils.getPath(this.oldLogDir));
     }
     if (!fs.delete(dir, true)) {
       LOG.info("Unable to delete " + dir);
     }
   }
 
   @Override
   public void close() throws IOException {
     if (this.closed) {
       return;
     }
     // When optionalFlushInterval is 0, the logSyncer is not started as a Thread.
     if (this.optionalFlushInterval > 0) {
       try {
         logSyncer.close();
         // Make sure we synced everything
         logSyncer.join(this.optionalFlushInterval * 2);
       } catch (InterruptedException e) {
         LOG.error("Exception while waiting for syncer thread to die", e);
         Thread.currentThread().interrupt();
       }
     }
     try {
       // Prevent all further flushing and rolling.
       closeBarrier.stopAndDrainOps();
     } catch (InterruptedException e) {
       LOG.error("Exception while waiting for cache flushes and log rolls", e);
       Thread.currentThread().interrupt();
     }
 
     // Tell our listeners that the log is closing
     if (!this.listeners.isEmpty()) {
       for (WALActionsListener i : this.listeners) {
         i.logCloseRequested();
       }
     }
     synchronized (updateLock) {
       this.closed = true;
       if (LOG.isDebugEnabled()) {
         LOG.debug("Closing WAL writer in " + this.dir.toString());
       }
       if (this.writer != null) {
         this.writer.close();
         this.writer = null;
       }
     }
   }
 
   /**
    * @param now
    * @param encodedRegionName Encoded name of the region as returned by
    * <code>HRegionInfo#getEncodedNameAsBytes()</code>.
    * @param tableName
    * @param clusterId
    * @return New log key.
    */
   protected HLogKey makeKey(byte[] encodedRegionName, byte[] tableName, long seqnum,
       long now, UUID clusterId) {
     return new HLogKey(encodedRegionName, tableName, seqnum, now, clusterId);
   }
 
   @Override
   public void append(HRegionInfo info, byte [] tableName, WALEdit edits,
     final long now, HTableDescriptor htd)
   throws IOException {
     append(info, tableName, edits, now, htd, true);
   }
 
   @Override
   public void append(HRegionInfo info, byte [] tableName, WALEdit edits,
     final long now, HTableDescriptor htd, boolean isInMemstore) throws IOException {
     append(info, tableName, edits, HConstants.DEFAULT_CLUSTER_ID, now, htd, true, isInMemstore);
   }
 
   /**
    * Append a set of edits to the log. Log edits are keyed by (encoded)
    * regionName, rowname, and log-sequence-id.
    *
    * Later, if we sort by these keys, we obtain all the relevant edits for a
    * given key-range of the HRegion (TODO). Any edits that do not have a
    * matching COMPLETE_CACHEFLUSH message can be discarded.
    *
    * <p>
    * Logs cannot be restarted once closed, or once the HLog process dies. Each
    * time the HLog starts, it must create a new log. This means that other
    * systems should process the log appropriately upon each startup (and prior
    * to initializing HLog).
    *
    * synchronized prevents appends during the completion of a cache flush or for
    * the duration of a log roll.
    *
    * @param info
    * @param tableName
    * @param edits
    * @param clusterId The originating clusterId for this edit (for replication)
    * @param now
    * @param doSync shall we sync?
    * @return txid of this transaction
    * @throws IOException
    */
   private long append(HRegionInfo info, byte [] tableName, WALEdit edits, UUID clusterId,
       final long now, HTableDescriptor htd, boolean doSync, boolean isInMemstore)
     throws IOException {
       if (edits.isEmpty()) return this.unflushedEntries.get();
       if (this.closed) {
         throw new IOException("Cannot append; log is closed");
       }
       long txid = 0;
       synchronized (this.updateLock) {
         long seqNum = obtainSeqNum();
         // The 'lastSeqWritten' map holds the sequence number of the oldest
         // write for each region (i.e. the first edit added to the particular
         // memstore). . When the cache is flushed, the entry for the
         // region being flushed is removed if the sequence number of the flush
         // is greater than or equal to the value in lastSeqWritten.
         // Use encoded name.  Its shorter, guaranteed unique and a subset of
         // actual  name.
         byte [] encodedRegionName = info.getEncodedNameAsBytes();
         if (isInMemstore) this.oldestUnflushedSeqNums.putIfAbsent(encodedRegionName, seqNum);
         HLogKey logKey = makeKey(encodedRegionName, tableName, seqNum, now, clusterId);
         doWrite(info, logKey, edits, htd);
         this.numEntries.incrementAndGet();
         txid = this.unflushedEntries.incrementAndGet();
         if (htd.isDeferredLogFlush()) {
           lastDeferredTxid = txid;
         }
       }
       // Sync if catalog region, and if not then check if that table supports
       // deferred log flushing
       if (doSync &&
           (info.isMetaRegion() ||
           !htd.isDeferredLogFlush())) {
         // sync txn to file system
         this.sync(txid);
       }
       return txid;
     }
 
   @Override
   public long appendNoSync(HRegionInfo info, byte [] tableName, WALEdit edits,
     UUID clusterId, final long now, HTableDescriptor htd)
     throws IOException {
     return append(info, tableName, edits, clusterId, now, htd, false, true);
   }
 
   /**
    * This class is responsible to hold the HLog's appended Entry list
    * and to sync them according to a configurable interval.
    *
    * Deferred log flushing works first by piggy backing on this process by
    * simply not sync'ing the appended Entry. It can also be sync'd by other
    * non-deferred log flushed entries outside of this thread.
    */
   class LogSyncer extends HasThread {
 
     private final long optionalFlushInterval;
 
     private final AtomicBoolean closeLogSyncer = new AtomicBoolean(false);
 
     // List of pending writes to the HLog. There corresponds to transactions
     // that have not yet returned to the client. We keep them cached here
     // instead of writing them to HDFS piecemeal, because the HDFS write
     // method is pretty heavyweight as far as locking is concerned. The
     // goal is to increase the batchsize for writing-to-hdfs as well as
     // sync-to-hdfs, so that we can get better system throughput.
     private List<Entry> pendingWrites = new LinkedList<Entry>();
 
     LogSyncer(long optionalFlushInterval) {
       this.optionalFlushInterval = optionalFlushInterval;
     }
 
     @Override
     public void run() {
       try {
         // awaiting with a timeout doesn't always
         // throw exceptions on interrupt
         while(!this.isInterrupted() && !closeLogSyncer.get()) {
 
           try {
             if (unflushedEntries.get() <= syncedTillHere) {
               synchronized (closeLogSyncer) {
                 closeLogSyncer.wait(this.optionalFlushInterval);
               }
             }
             // Calling sync since we waited or had unflushed entries.
             // Entries appended but not sync'd are taken care of here AKA
             // deferred log flush
             sync();
           } catch (IOException e) {
             LOG.error("Error while syncing, requesting close of hlog ", e);
             requestLogRoll();
             Threads.sleep(this.optionalFlushInterval);
           }
         }
       } catch (InterruptedException e) {
         LOG.debug(getName() + " interrupted while waiting for sync requests");
       } finally {
         LOG.info(getName() + " exiting");
       }
     }
 
     // appends new writes to the pendingWrites. It is better to keep it in
     // our own queue rather than writing it to the HDFS output stream because
     // HDFSOutputStream.writeChunk is not lightweight at all.
     synchronized void append(Entry e) throws IOException {
       pendingWrites.add(e);
     }
 
     // Returns all currently pending writes. New writes
     // will accumulate in a new list.
     synchronized List<Entry> getPendingWrites() {
       List<Entry> save = this.pendingWrites;
       this.pendingWrites = new LinkedList<Entry>();
       return save;
     }
 
     // writes out pending entries to the HLog
     void hlogFlush(Writer writer, List<Entry> pending) throws IOException {
       if (pending == null) return;
 
       // write out all accumulated Entries to hdfs.
       for (Entry e : pending) {
         writer.append(e);
       }
     }
 
     void close() {
       synchronized (closeLogSyncer) {
         closeLogSyncer.set(true);
         closeLogSyncer.notifyAll();
       }
     }
   }
 
   // sync all known transactions
   private void syncer() throws IOException {
     syncer(this.unflushedEntries.get()); // sync all pending items
   }
 
   // sync all transactions upto the specified txid
   private void syncer(long txid) throws IOException {
     // if the transaction that we are interested in is already
     // synced, then return immediately.
     if (txid <= this.syncedTillHere) {
       return;
     }
     Writer tempWriter;
     synchronized (this.updateLock) {
       if (this.closed) return;
       // Guaranteed non-null.
       // Note that parallel sync can close tempWriter.
       // The current method of dealing with this is to catch exceptions.
       // See HBASE-4387, HBASE-5623, HBASE-7329.
       tempWriter = this.writer;
     }
     try {
       long doneUpto;
       long now = EnvironmentEdgeManager.currentTimeMillis();
       // First flush all the pending writes to HDFS. Then
       // issue the sync to HDFS. If sync is successful, then update
       // syncedTillHere to indicate that transactions till this
       // number has been successfully synced.
       IOException ioe = null;
       List<Entry> pending = null;
       synchronized (flushLock) {
         if (txid <= this.syncedTillHere) {
           return;
         }
         doneUpto = this.unflushedEntries.get();
         pending = logSyncer.getPendingWrites();
         try {
           logSyncer.hlogFlush(tempWriter, pending);
         } catch(IOException io) {
           ioe = io;
           LOG.error("syncer encountered error, will retry. txid=" + txid, ioe);
         }
       }
       if (ioe != null && pending != null) {
         synchronized (this.updateLock) {
           synchronized (flushLock) {
             // HBASE-4387, HBASE-5623, retry with updateLock held
             tempWriter = this.writer;
             logSyncer.hlogFlush(tempWriter, pending);
           }
         }
       }
       // another thread might have sync'ed avoid double-sync'ing
       if (txid <= this.syncedTillHere) {
         return;
       }
       try {
         if (tempWriter != null) tempWriter.sync();
       } catch(IOException ex) {
         synchronized (this.updateLock) {
           // HBASE-4387, HBASE-5623, retry with updateLock held
           // TODO: we don't actually need to do it for concurrent close - what is the point
           //       of syncing new unrelated writer? Keep behavior for now.
           tempWriter = this.writer;
           if (tempWriter != null) tempWriter.sync();
         }
       }
       this.syncedTillHere = Math.max(this.syncedTillHere, doneUpto);
 
       this.metrics.finishSync(EnvironmentEdgeManager.currentTimeMillis() - now);
       // TODO: preserving the old behavior for now, but this check is strange. It's not
       //       protected by any locks here, so for all we know rolling locks might start
       //       as soon as we enter the "if". Is this best-effort optimization check?
       if (!this.logRollRunning) {
         checkLowReplication();
         try {
           if (tempWriter.getLength() > this.logrollsize) {
             requestLogRoll();
           }
         } catch (IOException x) {
           LOG.debug("Log roll failed and will be retried. (This is not an error)");
         }
       }
     } catch (IOException e) {
       LOG.fatal("Could not sync. Requesting roll of hlog", e);
       requestLogRoll();
       throw e;
     }
   }
 
   private void checkLowReplication() {
     // if the number of replicas in HDFS has fallen below the configured
     // value, then roll logs.
     try {
       int numCurrentReplicas = getLogReplication();
       if (numCurrentReplicas != 0
           && numCurrentReplicas < this.minTolerableReplication) {
         if (this.lowReplicationRollEnabled) {
           if (this.consecutiveLogRolls.get() < this.lowReplicationRollLimit) {
             LOG.warn("HDFS pipeline error detected. " + "Found "
                 + numCurrentReplicas + " replicas but expecting no less than "
                 + this.minTolerableReplication + " replicas. "
                 + " Requesting close of hlog.");
             requestLogRoll();
             // If rollWriter is requested, increase consecutiveLogRolls. Once it
             // is larger than lowReplicationRollLimit, disable the
             // LowReplication-Roller
             this.consecutiveLogRolls.getAndIncrement();
           } else {
             LOG.warn("Too many consecutive RollWriter requests, it's a sign of "
                 + "the total number of live datanodes is lower than the tolerable replicas.");
             this.consecutiveLogRolls.set(0);
             this.lowReplicationRollEnabled = false;
           }
         }
       } else if (numCurrentReplicas >= this.minTolerableReplication) {
 
         if (!this.lowReplicationRollEnabled) {
           // The new writer's log replicas is always the default value.
           // So we should not enable LowReplication-Roller. If numEntries
           // is lower than or equals 1, we consider it as a new writer.
           if (this.numEntries.get() <= 1) {
             return;
           }
           // Once the live datanode number and the replicas return to normal,
           // enable the LowReplication-Roller.
           this.lowReplicationRollEnabled = true;
           LOG.info("LowReplication-Roller was enabled.");
         }
       }
     } catch (Exception e) {
       LOG.warn("Unable to invoke DFSOutputStream.getNumCurrentReplicas" + e +
           " still proceeding ahead...");
     }
   }
 
   /**
    * This method gets the datanode replication count for the current HLog.
    *
    * If the pipeline isn't started yet or is empty, you will get the default
    * replication factor.  Therefore, if this function returns 0, it means you
    * are not properly running with the HDFS-826 patch.
    * @throws InvocationTargetException
    * @throws IllegalAccessException
    * @throws IllegalArgumentException
    *
    * @throws Exception
    */
   int getLogReplication()
   throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
     if (this.getNumCurrentReplicas != null && this.hdfs_out != null) {
       Object repl = this.getNumCurrentReplicas.invoke(getOutputStream(), NO_ARGS);
       if (repl instanceof Integer) {
         return ((Integer)repl).intValue();
       }
     }
     return 0;
   }
 
   boolean canGetCurReplicas() {
     return this.getNumCurrentReplicas != null;
   }
 
   @Override
   public void hsync() throws IOException {
     syncer();
   }
 
   @Override
   public void hflush() throws IOException {
     syncer();
   }
 
   @Override
   public void sync() throws IOException {
     syncer();
   }
 
   @Override
   public void sync(long txid) throws IOException {
     syncer(txid);
   }
 
   private void requestLogRoll() {
     if (!this.listeners.isEmpty()) {
       for (WALActionsListener i: this.listeners) {
         i.logRollRequested();
       }
     }
   }
 
   // TODO: Remove info.  Unused.
   protected void doWrite(HRegionInfo info, HLogKey logKey, WALEdit logEdit,
                            HTableDescriptor htd)
   throws IOException {
     if (!this.enabled) {
       return;
     }
     if (!this.listeners.isEmpty()) {
       for (WALActionsListener i: this.listeners) {
         i.visitLogEntryBeforeWrite(htd, logKey, logEdit);
       }
     }
     try {
       long now = EnvironmentEdgeManager.currentTimeMillis();
       // coprocessor hook:
       if (!coprocessorHost.preWALWrite(info, logKey, logEdit)) {
         if (logEdit.isReplay()) {
           // set replication scope null so that this won't be replicated
           logKey.setScopes(null);
         }
         // write to our buffer for the Hlog file.
         logSyncer.append(new FSHLog.Entry(logKey, logEdit));
       }
       long took = EnvironmentEdgeManager.currentTimeMillis() - now;
       coprocessorHost.postWALWrite(info, logKey, logEdit);
       long len = 0;
       for (KeyValue kv : logEdit.getKeyValues()) {
         len += kv.getLength();
       }
       this.metrics.finishAppend(took, len);
     } catch (IOException e) {
       LOG.fatal("Could not append. Requesting close of hlog", e);
       requestLogRoll();
       throw e;
     }
   }
 
 
   /** @return How many items have been added to the log */
   int getNumEntries() {
     return numEntries.get();
   }
 
   @Override
   public long obtainSeqNum() {
     return this.logSeqNum.incrementAndGet();
   }
 
   /** @return the number of log files in use */
   int getNumLogFiles() {
     return outputfiles.size();
   }
 
   @Override
   public Long startCacheFlush(final byte[] encodedRegionName) {
     Long oldRegionSeqNum = null;
     if (!closeBarrier.beginOp()) {
       return null;
     }
     synchronized (oldestSeqNumsLock) {
       oldRegionSeqNum = this.oldestUnflushedSeqNums.remove(encodedRegionName);
       if (oldRegionSeqNum != null) {
         Long oldValue = this.oldestFlushingSeqNums.put(encodedRegionName, oldRegionSeqNum);
         assert oldValue == null : "Flushing map not cleaned up for "
           + Bytes.toString(encodedRegionName);
       }
     }
     if (oldRegionSeqNum == null) {
       // TODO: if we have no oldRegionSeqNum, and WAL is not disabled, presumably either
       //       the region is already flushing (which would make this call invalid), or there
       //       were no appends after last flush, so why are we starting flush? Maybe we should
       //       assert not null, and switch to "long" everywhere. Less rigorous, but safer,
       //       alternative is telling the caller to stop. For now preserve old logic.
       LOG.warn("Couldn't find oldest seqNum for the region we are about to flush: ["
         + Bytes.toString(encodedRegionName) + "]");
     }
     return obtainSeqNum();
   }
 
   @Override
   public void completeCacheFlush(final byte [] encodedRegionName)
   {
     synchronized (oldestSeqNumsLock) {
       this.oldestFlushingSeqNums.remove(encodedRegionName);
     }
     closeBarrier.endOp();
   }
 
   @Override
   public void abortCacheFlush(byte[] encodedRegionName) {
     Long currentSeqNum = null, seqNumBeforeFlushStarts = null;
     synchronized (oldestSeqNumsLock) {
       seqNumBeforeFlushStarts = this.oldestFlushingSeqNums.remove(encodedRegionName);
       if (seqNumBeforeFlushStarts != null) {
         currentSeqNum =
           this.oldestUnflushedSeqNums.put(encodedRegionName, seqNumBeforeFlushStarts);
       }
     }
     closeBarrier.endOp();
     if ((currentSeqNum != null)
         && (currentSeqNum.longValue() <= seqNumBeforeFlushStarts.longValue())) {
       String errorStr = "Region " + Bytes.toString(encodedRegionName) +
           "acquired edits out of order current memstore seq=" + currentSeqNum
           + ", previous oldest unflushed id=" + seqNumBeforeFlushStarts;
       LOG.error(errorStr);
       assert false : errorStr;
       Runtime.getRuntime().halt(1);
     }
   }
 
   @Override
   public boolean isLowReplicationRollEnabled() {
       return lowReplicationRollEnabled;
   }
 
   /**
    * Get the directory we are making logs in.
    *
    * @return dir
    */
   protected Path getDir() {
     return dir;
   }
 
   static Path getHLogArchivePath(Path oldLogDir, Path p) {
     return new Path(oldLogDir, p.getName());
   }
 
   static String formatRecoveredEditsFileName(final long seqid) {
     return String.format("%019d", seqid);
   }
 
   public static final long FIXED_OVERHEAD = ClassSize.align(
     ClassSize.OBJECT + (5 * ClassSize.REFERENCE) +
     ClassSize.ATOMIC_INTEGER + Bytes.SIZEOF_INT + (3 * Bytes.SIZEOF_LONG));
 
   private static void usage() {
     System.err.println("Usage: HLog <ARGS>");
     System.err.println("Arguments:");
     System.err.println(" --dump  Dump textual representation of passed one or more files");
     System.err.println("         For example: HLog --dump hdfs://example.com:9000/hbase/.logs/MACHINE/LOGFILE");
     System.err.println(" --split Split the passed directory of WAL logs");
     System.err.println("         For example: HLog --split hdfs://example.com:9000/hbase/.logs/DIR");
   }
 
   private static void split(final Configuration conf, final Path p)
   throws IOException {
     FileSystem fs = FileSystem.get(conf);
     if (!fs.exists(p)) {
       throw new FileNotFoundException(p.toString());
     }
     final Path baseDir = FSUtils.getRootDir(conf);
     final Path oldLogDir = new Path(baseDir, HConstants.HREGION_OLDLOGDIR_NAME);
     if (!fs.getFileStatus(p).isDir()) {
       throw new IOException(p + " is not a directory");
     }
 
     HLogSplitter logSplitter = HLogSplitter.createLogSplitter(
         conf, baseDir, p, oldLogDir, fs);
     logSplitter.splitLog();
   }
 
   @Override
   public WALCoprocessorHost getCoprocessorHost() {
     return coprocessorHost;
   }
 
   /** Provide access to currently deferred sequence num for tests */
   boolean hasDeferredEntries() {
     return lastDeferredTxid > syncedTillHere;
   }
 
   @Override
   public long getEarliestMemstoreSeqNum(byte[] encodedRegionName) {
     Long result = oldestUnflushedSeqNums.get(encodedRegionName);
     return result == null ? HConstants.NO_SEQNUM : result.longValue();
   }
 
   /**
    * Pass one or more log file names and it will either dump out a text version
    * on <code>stdout</code> or split the specified log files.
    *
    * @param args
    * @throws IOException
    */
   public static void main(String[] args) throws IOException {
     if (args.length < 2) {
       usage();
       System.exit(-1);
     }
     // either dump using the HLogPrettyPrinter or split, depending on args
     if (args[0].compareTo("--dump") == 0) {
       HLogPrettyPrinter.run(Arrays.copyOfRange(args, 1, args.length));
     } else if (args[0].compareTo("--split") == 0) {
       Configuration conf = HBaseConfiguration.create();
       for (int i = 1; i < args.length; i++) {
         try {
           Path logPath = new Path(args[i]);
           FSUtils.setFsDefault(conf, logPath);
           split(conf, logPath);
         } catch (Throwable t) {
           t.printStackTrace(System.err);
           System.exit(-1);
         }
       }
     } else {
       usage();
       System.exit(-1);
     }
   }
 }