4.1 程序入口

Kafka.scala

def main(args: Array[String]): Unit = {
  try {
    // 获取参数相关信息
    val serverProps = getPropsFromArgs(args)
    // 配置服务
    val server = buildServer(serverProps)

    try {
      if (!OperatingSystem.IS_WINDOWS && !Java.isIbmJdk)
        new LoggingSignalHandler().register()
    } catch {
      case e: ReflectiveOperationException =>
        warn("Failed to register optional signal handler that logs a message when the process is terminated " +
          s"by a signal. Reason for registration failure is: $e", e)
    }

    // attach shutdown handler to catch terminating signals as well as normal termination
    Exit.addShutdownHook("kafka-shutdown-hook", {
      try server.shutdown()
      catch {
        case _: Throwable =>
          fatal("Halting Kafka.")
          // Calling exit() can lead to deadlock as exit() can be called multiple times. Force exit.
          Exit.halt(1)
      }
    })

    // 启动服务
    try server.startup()
    catch {
      case _: Throwable =>
        // KafkaServer.startup() calls shutdown() in case of exceptions, so we invoke `exit` to set the status code
        fatal("Exiting Kafka.")
        Exit.exit(1)
    }

    server.awaitShutdown()
  }
  catch {
    case e: Throwable =>
      fatal("Exiting Kafka due to fatal exception", e)
      Exit.exit(1)
  }
  Exit.exit(0)
}