@Test
 public void testEmptyLogDir() throws Exception {
   LOG.info("testEmptyLogDir");
   slm = new SplitLogManager(zkw, conf, stopper, "dummy-master", null);
   slm.finishInitialization();
   FileSystem fs = TEST_UTIL.getTestFileSystem();
   Path emptyLogDirPath = new Path(fs.getWorkingDirectory(), UUID.randomUUID().toString());
   fs.mkdirs(emptyLogDirPath);
   slm.splitLogDistributed(emptyLogDirPath);
   assertFalse(fs.exists(emptyLogDirPath));
 }
  public void splitLog(final List<ServerName> serverNames) throws IOException {
    long splitTime = 0, splitLogSize = 0;
    List<Path> logDirs = new ArrayList<Path>();
    for(ServerName serverName: serverNames){
      Path logDir = new Path(this.rootdir,
        HLog.getHLogDirectoryName(serverName.toString()));
      Path splitDir = logDir.suffix(HLog.SPLITTING_EXT);
      // rename the directory so a rogue RS doesn't create more HLogs
      if (fs.exists(logDir)) {
        if (!this.fs.rename(logDir, splitDir)) {
          throw new IOException("Failed fs.rename for log split: " + logDir);
        }
        logDir = splitDir;
        LOG.debug("Renamed region directory: " + splitDir);
      } else if (!fs.exists(splitDir)) {
        LOG.info("Log dir for server " + serverName + " does not exist");
        continue;
      }
      logDirs.add(splitDir);
    }

    if (logDirs.isEmpty()) {
      LOG.info("No logs to split");
      return;
    }

    if (distributedLogSplitting) {
      splitLogManager.handleDeadWorkers(serverNames);
      splitTime = EnvironmentEdgeManager.currentTimeMillis();
      splitLogSize = splitLogManager.splitLogDistributed(logDirs);
      splitTime = EnvironmentEdgeManager.currentTimeMillis() - splitTime;
    } else {
      for(Path logDir: logDirs){
        // splitLogLock ensures that dead region servers' logs are processed
        // one at a time
        this.splitLogLock.lock();
        try {
          HLogSplitter splitter = HLogSplitter.createLogSplitter(
            conf, rootdir, logDir, oldLogDir, this.fs);
          try {
            // If FS is in safe mode, just wait till out of it.
            FSUtils.waitOnSafeMode(conf, conf.getInt(HConstants.THREAD_WAKE_FREQUENCY, 1000));
            splitter.splitLog();
          } catch (OrphanHLogAfterSplitException e) {
            LOG.warn("Retrying splitting because of:", e);
            //An HLogSplitter instance can only be used once.  Get new instance.
            splitter = HLogSplitter.createLogSplitter(conf, rootdir, logDir,
              oldLogDir, this.fs);
            splitter.splitLog();
          }
          splitTime = splitter.getTime();
          splitLogSize = splitter.getSize();
        } finally {
          this.splitLogLock.unlock();
        }
      }
    }

    if (this.metrics != null) {
      this.metrics.addSplit(splitTime, splitLogSize);
    }
  }