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。