[KAFKA-1414] Speedup broker startup after hard reset - ASF JIRA

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Details

Type: Improvement
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: 0.8.1.1, 0.8.2.0, 0.10.1.0
Fix Version/s: 0.8.2.0
Component/s: log
Labels:
None

Description

After hard reset due to power failure broker takes way too much time recovering unflushed segments in a single thread. This could be easiliy improved launching multiple threads (one per data dirrectory, assuming that typically each data directory is on a dedicated drive). Localy we trie this simple patch to LogManager.loadLogs and it seems to work, however I'm too new to scala, so do not take it literally:

  /**
   * Recover and load all logs in the given data directories
   */
  private def loadLogs(dirs: Seq[File]) {
    val threads : Array[Thread] = new Array[Thread](dirs.size)
    var i: Int = 0
    val me = this

    for(dir <- dirs) {
      val thread = new Thread( new Runnable {
        def run()
        {
          val recoveryPoints = me.recoveryPointCheckpoints(dir).read
          /* load the logs */
          val subDirs = dir.listFiles()
          if(subDirs != null) {
            val cleanShutDownFile = new File(dir, Log.CleanShutdownFile)
            if(cleanShutDownFile.exists())
              info("Found clean shutdown file. Skipping recovery for all logs in data directory '%s'".format(dir.getAbsolutePath))
            for(dir <- subDirs) {
              if(dir.isDirectory) {
                info("Loading log '" + dir.getName + "'")
                val topicPartition = Log.parseTopicPartitionName(dir.getName)
                val config = topicConfigs.getOrElse(topicPartition.topic, defaultConfig)
                val log = new Log(dir,
                  config,
                  recoveryPoints.getOrElse(topicPartition, 0L),
                  scheduler,
                  time)
                val previous = addLogWithLock(topicPartition, log)
                if(previous != null)
                  throw new IllegalArgumentException("Duplicate log directories found: %s, %s!".format(log.dir.getAbsolutePath, previous.dir.getAbsolutePath))
              }
            }
            cleanShutDownFile.delete()
          }
        }
      })

      thread.start()
      threads(i) = thread
      i = i + 1
    }

    for(thread <- threads) {
      thread.join()
    }
  }

  def addLogWithLock(topicPartition: TopicAndPartition, log: Log): Log = {
    logCreationOrDeletionLock synchronized {
      this.logs.put(topicPartition, log)
    }
  }