kafka源码解析之三Broker的启动

正常启动kafka的命令如下：

查看kafka-server-start.sh脚本：

查看Kafka.Kafka类：

object Kafka extends Logging {

  def main(args: Array[String]): Unit = {
    if (args.length != 1) {
      println("USAGE: java [options] %s server.properties".format(classOf[KafkaServer].getSimpleName()))
      System.exit(1)
    }
    try {
      val props = Utils.loadProps(args(0))
      val serverConfig = new KafkaConfig(props)//组装配置信息
      KafkaMetricsReporter.startReporters(serverConfig.props)
      val kafkaServerStartable = new KafkaServerStartable(serverConfig)
      // attach shutdown handler to catch control-c
      Runtime.getRuntime().addShutdownHook(new Thread() {
        override def run() = {
          kafkaServerStartable.shutdown//注册shutdown时候的钩子函数
        }
      })
      kafkaServerStartable.startup//启动kafkaServerStartable
      kafkaServerStartable.awaitShutdown//正常情况下broker一直在这里wait
    }
    catch {
      case e: Throwable => fatal(e)
    }
    System.exit(0)
  }
}

其中上面的kafkaServerStartable封装了KafkaServer，最终执行startup的是KafkaServer。

class KafkaServerStartable(val serverConfig: KafkaConfig) extends Logging {
  private val server = new KafkaServer(serverConfig)
  def startup() {
    try {
      server.startup()
      AppInfo.registerInfo()
    }
    catch {
      case e: Throwable =>
        fatal("Fatal error during KafkaServerStartable startup. Prepare to shutdown", e)
        // KafkaServer already calls shutdown() internally, so this is purely for logging & the exit code
        System.exit(1)
    }
  }
}
查看KafkaServer：
class KafkaServer(val config: KafkaConfig, time: Time = SystemTime) extends Logging with KafkaMetricsGroup {
  this.logIdent = "[Kafka Server " + config.brokerId + "], "
  private var isShuttingDown = new AtomicBoolean(false)
  private var shutdownLatch = new CountDownLatch(1)
  private var startupComplete = new AtomicBoolean(false)
  val brokerState: BrokerState = new BrokerState
  val correlationId: AtomicInteger = new AtomicInteger(0)
  var socketServer: SocketServer = null
  var requestHandlerPool: KafkaRequestHandlerPool = null
  var logManager: LogManager = null
  var offsetManager: OffsetManager = null
  var kafkaHealthcheck: KafkaHealthcheck = null
  var topicConfigManager: TopicConfigManager = null
  var replicaManager: ReplicaManager = null
  var apis: KafkaApis = null
  var kafkaController: KafkaController = null
  val kafkaScheduler = new KafkaScheduler(config.backgroundThreads)
  var zkClient: ZkClient = null
  newGauge(
    "BrokerState",
    new Gauge[Int] {
      def value = brokerState.currentState
    }
  )
  /**
   * Start up API for bringing up a single instance of the Kafka server.
   * Instantiates the LogManager, the SocketServer and the request handlers - KafkaRequestHandlers
   */
  def startup() {
    try {
      info("starting")
      brokerState.newState(Starting)
      isShuttingDown = new AtomicBoolean(false)
      shutdownLatch = new CountDownLatch(1)
      /* start scheduler */
      kafkaScheduler.startup()
      /* setup zookeeper */
      zkClient = initZk()
      /* start log manager */
      logManager = createLogManager(zkClient, brokerState)
      logManager.startup()
      socketServer = new SocketServer(config.brokerId,
        config.hostName,
        config.port,
        config.numNetworkThreads,
        config.queuedMaxRequests,
        config.socketSendBufferBytes,
        config.socketReceiveBufferBytes,
        config.socketRequestMaxBytes,
        config.maxConnectionsPerIp,
        config.connectionsMaxIdleMs,
        config.maxConnectionsPerIpOverrides)
      socketServer.startup()
      //1.作为备：fetch 消息，跟上leader 2.作为主：刷新ISR
      replicaManager = new ReplicaManager(config, time, zkClient, kafkaScheduler, logManager, isShuttingDown)
      /* start offset manager */
      //1.保存offsetsCache = new Pool[GroupTopicPartition, OffsetAndMetadata]
      //2.删除过期的offsetsCache
      offsetManager = createOffsetManager()
      kafkaController = new KafkaController(config, zkClient, brokerState)
      /* start processing requests */
      apis = new KafkaApis(socketServer.requestChannel, replicaManager, offsetManager, zkClient, config.brokerId, config, kafkaController)
      requestHandlerPool = new KafkaRequestHandlerPool(config.brokerId, socketServer.requestChannel, apis, config.numIoThreads)
      brokerState.newState(RunningAsBroker)
      Mx4jLoader.maybeLoad()
      replicaManager.startup()
      kafkaController.startup()
      //处理topic的config改变通知
      topicConfigManager = new TopicConfigManager(zkClient, logManager)
      topicConfigManager.startup()
      /* tell everyone we are alive */
      //在/broker/id节点建立kafka的broker信息
      kafkaHealthcheck = new KafkaHealthcheck(config.brokerId, config.advertisedHostName, config.advertisedPort, config.zkSessionTimeoutMs, zkClient)
      kafkaHealthcheck.startup()
      registerStats()
      startupComplete.set(true)
      info("started")
    }
    catch {
      case e: Throwable =>
        fatal("Fatal error during KafkaServer startup. Prepare to shutdown", e)
        shutdown()
        throw e
    }
  }
}
执行完之后，Broker上的KafkaServer正式启动。