kafka KafkaRequestHandlerPool类

KafkaRequestHandlerPool是KafkaRequestHandler的handler池，处理所有请求队列

具体的处理，会交由KafkaApis类

for(i <- 0 until numThreads) {
    runnables(i) = new KafkaRequestHandler(i, brokerId, aggregateIdleMeter, numThreads, requestChannel, apis)
    threads(i) = Utils.daemonThread("kafka-request-handler-" + i, runnables(i))
    threads(i).start()
  }

run方法：

def run() {
    while(true) {
      try {
        var req : RequestChannel.Request = null
        while (req == null) {
          //获得请求
          // We use a single meter for aggregate idle percentage for the thread pool.
          // Since meter is calculated as total_recorded_value / time_window and
          // time_window is independent of the number of threads, each recorded idle
          // time should be discounted by # threads.
          val startSelectTime = SystemTime.nanoseconds
          req = requestChannel.receiveRequest(300)//blockqueue poll 获得请求request
          val idleTime = SystemTime.nanoseconds - startSelectTime
          aggregateIdleMeter.mark(idleTime / totalHandlerThreads)
        }

        //处理
        if(req eq RequestChannel.AllDone) {
          debug("Kafka request handler %d on broker %d received shut down command".format(
            id, brokerId))
          return
        }
        req.requestDequeueTimeMs = SystemTime.milliseconds
        trace("Kafka request handler %d on broker %d handling request %s".format(id, brokerId, req))
        //交由apis类负责处理request
        apis.handle(req)
      } catch {
        case e: Throwable => error("Exception when handling request", e)
      }
    }
  }