startServer.scala

def startServer(serverStartFunc: () => Unit) {
  val serverStarted = new Semaphore(0)
  var serverStartException: Option[Exception] = None

  startThread("startZookeeper") {
    try {
      log.info("Starting ZooKeeper server. clientPort=" + clientPort  + 
        " class=" + zkServer.getClass.getName)
      serverStartFunc()
      serverStarted.release()
    } catch {
      case ioex: IOException =>
        log.error("ZooKeeper Failed - data directory corruption: " + 
          ioex.getMessage, ioex)
        serverStartException = Some(ioex)
      case ex: Exception =>
        log.error("ZooKeeper Failed: " + ex.getMessage, ex)
        serverStartException = Some(ex)
    }
  }

  if (!serverStarted.tryAcquire(waitingSec, TimeUnit.SECONDS)) {
    serverStartException match {
      case Some(ex) => throw new RuntimeException(ex)
      case None =>
    }
  }
}