kafka TopicConfigManager类

topicconfigManager类

主要流程为

1.监控config/change节点，那个topic的config变化了

2.从zk上的topic的config目录，获取最新config信息

3.更新logmanager里指定topic的tplog（每个topic每个partition对应一个log）配置

/**
   * 注册config change的listener
   * Begin watching for config changes
   */
  def startup() {
    ZkUtils.makeSurePersistentPathExists(zkClient, ZkUtils.TopicConfigChangesPath)
    //监听/config/changes的子节点,ConfigChangeListener
    zkClient.subscribeChildChanges(ZkUtils.TopicConfigChangesPath, ConfigChangeListener)
    //启动服务，检查是否有topic的config需要更新，使用跟ConfigChangeListener相同的方法processConfigChanges
    processAllConfigChanges()
  }

主要方法processConfigChanges

/**
   * change config topic需要
   * 1.设置zk上的topic config；
   * 2.在zk上添加一个notification，标志哪个topic的config被改变
   * Process the given list of config changes
   */
  private def processConfigChanges(notifications: Seq[String]) {
    if (notifications.size > 0) {
      info("Processing config change notification(s)...")
      val now = time.milliseconds
      val logs = logManager.logsByTopicPartition.toBuffer
      //group by topic,Buffer[Log]                         buffer._2 := Log
      val logsByTopic = logs.groupBy(_._1.topic).mapValues(_.map(_._2))
      for (notification <- notifications) {
        val changeId = changeNumber(notification)
        if (changeId > lastExecutedChange) {//changeid是比现在新的
          val changeZnode = ZkUtils.TopicConfigChangesPath + "/" + notification
          val (jsonOpt, stat) = ZkUtils.readDataMaybeNull(zkClient, changeZnode)
          if(jsonOpt.isDefined) {
            val json = jsonOpt.get
            val topic = json.substring(1, json.length - 1) // hacky way to dequote
            if (logsByTopic.contains(topic)) {
              /* combine the default properties with the overrides in zk to create the new LogConfig */
              val props = new Properties(logManager.defaultConfig.toProps)
              props.putAll(AdminUtils.fetchTopicConfig(zkClient, topic))//获得最新topic config和default prop的合并值
              val logConfig = LogConfig.fromProps(props)
              for (log <- logsByTopic(topic))//获得当前logmanager对象中所有这个topic的log对象
                log.config = logConfig
              info("Processed topic config change %d for topic %s, setting new config to %s.".format(changeId, topic, props))
              purgeObsoleteNotifications(now, notifications)
            }
          }
          lastExecutedChange = changeId
        }
      }
    }
  }