kafka broker宕机&leader选举

broker change是由BrokerChangeListener监听类，监听/brokers/ids下得brokerid

BrokerChangeListener的handleChildChange

将新的死的broker交由controller管理

class BrokerChangeListener() extends IZkChildListener with Logging {
    this.logIdent = "[BrokerChangeListener on Controller " + controller.config.brokerId + "]: "
    def handleChildChange(parentPath : String, currentBrokerList : java.util.List[String]) {
      info("Broker change listener fired for path %s with children %s".format(parentPath, currentBrokerList.mkString(",")))
      inLock(controllerContext.controllerLock) {
        if (hasStarted.get) {
          ControllerStats.leaderElectionTimer.time {
            try {
              val curBrokerIds = currentBrokerList.map(_.toInt).toSet
              val newBrokerIds = curBrokerIds -- controllerContext.liveOrShuttingDownBrokerIds
              val newBrokerInfo = newBrokerIds.map(ZkUtils.getBrokerInfo(zkClient, _))
              val newBrokers = newBrokerInfo.filter(_.isDefined).map(_.get)
              val deadBrokerIds = controllerContext.liveOrShuttingDownBrokerIds -- curBrokerIds
              controllerContext.liveBrokers = curBrokerIds.map(ZkUtils.getBrokerInfo(zkClient, _)).filter(_.isDefined).map(_.get)
              info("Newly added brokers: %s, deleted brokers: %s, all live brokers: %s"
                .format(newBrokerIds.mkString(","), deadBrokerIds.mkString(","), controllerContext.liveBrokerIds.mkString(",")))
              newBrokers.foreach(controllerContext.controllerChannelManager.addBroker(_))
              deadBrokerIds.foreach(controllerContext.controllerChannelManager.removeBroker(_))
              //将变化的broker，交由controller管理
              if(newBrokerIds.size > 0)
                controller.onBrokerStartup(newBrokerIds.toSeq)
              if(deadBrokerIds.size > 0)
                controller.onBrokerFailure(deadBrokerIds.toSeq)
            } catch {
              case e: Throwable => error("Error while handling broker changes", e)
            }
          }
        }
      }
    }

kafkacontroller的onBrokerFailure

def onBrokerFailure(deadBrokers: Seq[Int]) {
    info("Broker failure callback for %s".format(deadBrokers.mkString(",")))
    val deadBrokersThatWereShuttingDown =
      deadBrokers.filter(id => controllerContext.shuttingDownBrokerIds.remove(id))
    info("Removed %s from list of shutting down brokers.".format(deadBrokersThatWereShuttingDown))
    val deadBrokersSet = deadBrokers.toSet
    // trigger OfflinePartition state for all partitions whose current leader is one amongst the dead brokers
    // 先处理死掉的broker上的leader的tp
    val partitionsWithoutLeader = controllerContext.partitionLeadershipInfo.filter(partitionAndLeader =>
      deadBrokersSet.contains(partitionAndLeader._2.leaderAndIsr.leader) &&
        !deleteTopicManager.isTopicQueuedUpForDeletion(partitionAndLeader._1.topic)).keySet
    //下线tp，没有meta信息更新，不发送
    partitionStateMachine.handleStateChanges(partitionsWithoutLeader, OfflinePartition)
    // trigger OnlinePartition state changes for offline or new partitions
    //上线选举leader，并上线，更新各个broker meta信息
    partitionStateMachine.triggerOnlinePartitionStateChange()
    // filter out the replicas that belong to topics that are being deleted
    var allReplicasOnDeadBrokers = controllerContext.replicasOnBrokers(deadBrokersSet)
    val activeReplicasOnDeadBrokers = allReplicasOnDeadBrokers.filterNot(p => deleteTopicManager.isTopicQueuedUpForDeletion(p.topic))
    // handle dead replicas 处理死掉的replica（所有）
    replicaStateMachine.handleStateChanges(activeReplicasOnDeadBrokers, OfflineReplica)
    // check if topic deletion state for the dead replicas needs to be updated
    val replicasForTopicsToBeDeleted = allReplicasOnDeadBrokers.filter(p => deleteTopicManager.isTopicQueuedUpForDeletion(p.topic))
    if(replicasForTopicsToBeDeleted.size > 0) {
      // it is required to mark the respective replicas in TopicDeletionFailed state since the replica cannot be
      // deleted when the broker is down. This will prevent the replica from being in TopicDeletionStarted state indefinitely
      // since topic deletion cannot be retried until at least one replica is in TopicDeletionStarted state
      deleteTopicManager.failReplicaDeletion(replicasForTopicsToBeDeleted)
    }
  }

   

  PartitionStateMachine的triggerOnlinePartitionStateChange，调用方法是将新的leader上线

  调用electLeaderForPartition

     val (leaderAndIsr, replicas) = leaderSelector.selectLeader(topicAndPartition, currentLeaderAndIsr)
        val (updateSucceeded, newVersion) = ReplicationUtils.updateLeaderAndIsr(zkClient, topic, partition,
          leaderAndIsr, controller.epoch, currentLeaderAndIsr.zkVersion)
        newLeaderAndIsr = leaderAndIsr
        newLeaderAndIsr.zkVersion = newVersion
        
        // update the leader cache
      controllerContext.partitionLeadershipInfo.put(TopicAndPartition(topic, partition), newLeaderIsrAndControllerEpoch)
      stateChangeLogger.trace("Controller %d epoch %d elected leader %d for Offline partition %s"
                                .format(controllerId, controller.epoch, newLeaderAndIsr.leader, topicAndPartition))
      val replicas = controllerContext.partitionReplicaAssignment(TopicAndPartition(topic, partition))
      // store new leader and isr info in cache 更新broker元数据信息 updateMetadataRequestMap
      brokerRequestBatch.addLeaderAndIsrRequestForBrokers(replicasForThisPartition, topic, partition,
        newLeaderIsrAndControllerEpoch, replicas)

   partitionStateMachine的leaderselect变量OfflinePartitionLeaderSelector

选举broker上的tp的新leader

          case false =>
            //选择在线broker中得replica的第一个作为leader
            val liveReplicasInIsr = liveAssignedReplicas.filter(r => liveBrokersInIsr.contains(r))
            val newLeader = liveReplicasInIsr.head
            debug("Some broker in ISR is alive for %s. Select %d from ISR %s to be the leader."
                  .format(topicAndPartition, newLeader, liveBrokersInIsr.mkString(",")))
            new LeaderAndIsr(newLeader, currentLeaderEpoch + 1, liveBrokersInIsr.toList, currentLeaderIsrZkPathVersion + 1)
        }
        info("Selected new leader and ISR %s for offline partition %s".format(newLeaderAndIsr.toString(), topicAndPartition))
        (newLeaderAndIsr, liveAssignedReplicas)