- 许久不写字,发现写作水平严重退步啊~~~
- 以前也是个文艺青年,现在也要写出诗意的代码啊~
- 没找到以前写的诗,咱们还是一起撸代码吧...
Kafka网络层一哥:SocketServer类
- 所在文件: core/src/main/scala/kafka/network/SocketServer.scala;
- 统筹组织所有的网络层组件;
-
startup()方法:
(1) 根据配置的若干endpoint创建相应的Acceptor及相关联的一组Processor线程;
for (i <- processorBeginIndex until processorEndIndex) {
processors(i) = new Processor(i,
time,
maxRequestSize,
requestChannel,
connectionQuotas,
connectionsMaxIdleMs,
protocol,
config.values,
metrics
)
}
val acceptor = new Acceptor(endpoint, sendBufferSize, recvBufferSize, brokerId,
processors.slice(processorBeginIndex, processorEndIndex), connectionQuotas)
(2) 创建Acceptor运行的线程并启动;
Utils.newThread("kafka-socket-acceptor-%s-%d".format(protocol.toString,
endpoint.port), acceptor, false).start()
acceptor.awaitStartup()
Kafka网络层头号马仔:Acceptor类
- 所在文件: core/src/main/scala/kafka/network/SocketServer.scala
-
Acceptor类对象创建:
(1) 创建监听ServerSocket:
val serverChannel = ServerSocketChannel.open()
serverChannel.configureBlocking(false)
serverChannel.socket().setReceiveBufferSize(recvBufferSize)
try {
serverChannel.socket.bind(socketAddress)
info("Awaiting socket connections on %s:%d.".format(socketAddress.getHostName, serverChannel.socket.getLocalPort))
} catch {
case e: SocketException =>
throw new KafkaException("Socket server failed to bind to %s:%d: %s.".format(socketAddress.getHostName, port, e.getMessage), e)
}
(2) 开启分配到的若干Processor:
this.synchronized {
processors.foreach { processor =>
Utils.newThread("kafka-network-thread-%d-%s-%d".format(brokerId, endPoint.protocolType.toString, processor.id), processor, false).start()
}
}
(3) run()-利用NIO的selector来接收网络连接:
var currentProcessor = 0
while (isRunning) {
try {
val ready = nioSelector.select(500)
if (ready > 0) {
val keys = nioSelector.selectedKeys()
val iter = keys.iterator()
while (iter.hasNext && isRunning) {
try {
val key = iter.next
iter.remove()
if (key.isAcceptable)
accept(key, processors(currentProcessor))
else
throw new IllegalStateException("Unrecognized key state for acceptor thread.")
// round robin to the next processor thread
currentProcessor = (currentProcessor + 1) % processors.length
} catch {
case e: Throwable => error("Error while accepting connection", e)
}
}
}
}
这里面最主要的就是accept(key, processors(currentProcessor))
(4) accept: 设置新连接socket的参数后交由Processor处理:
socketChannel.configureBlocking(false)
socketChannel.socket().setTcpNoDelay(true)
socketChannel.socket().setKeepAlive(true)
socketChannel.socket().setSendBufferSize(sendBufferSize)
processor.accept(socketChannel)
Kafka网络层堂口扛把子:Processor类
- 所在文件:core/src/main/scala/kafka/network/SocketServer.scala;
- 从单个连接进来的request都由它处理;
- 每个Processor对象会创建自己的nio selector;
- 每个连接有唯一标识ConnectionId:
$localHost:$localPort-$remoteHost:$remotePort,这个非常重要!!! - accept(socketChannel::SocketChannel):将新连接的SocketChannel保存到并发队列Q1中;
-
run()是核心, 包裹在一个循环里,直接线程退出,
while(isRunning) {},里面依次调用如下函数:
(1) configureNewConnections():从并发队列Q1里取出SocketChannel,添加到自身的nio selector中,监听读事件;
(2) processNewResponses():处理当前所有处理完成的request相应的response, 这些response都是从RequestChannel获得(requestChannel.receiveResponse),根据request的类型来决定从当前连接的nio selector中暂时删除读事件监听/添加写事件/关闭当前连接;
(3) selector.poll(300): 这个就不用解释了, 这个selector是对nio selector的又一封装,我们后面一章会讲到,它完成具体的数据接收和发送;
(4)selector.completedReceives.asScala.foreach: 处理当前所有的从selector返回的完整request,将其put到RequestChannel的一个阻塞队列里,供应用层获取并处理;同时会暂时删除些连接上的读事件监听:selector.mute(receive.source);
(5)selector.completedSends.asScala.foreach: 处理当前所有的从selector返回的写操作,重新将读事件添加到连接的selector监听中selector.unmute(send.destination);
(6)selector.disconnected.asScala.foreach: 处理当前所有将关闭的连接;
Kafka网络层中间人:RequestChannel类
- 所在文件: core/src/main/scala/kafka/network/RequestChannel.scala;
- 保存所有从网络层拿到的完整request和需要发送的response;
- 一般是RequestHandler会周期性从RequestChannel获取request,并将response保存回RequestChannel;
- processNewResponses() 处理RequestChannel中所有的response;
Kafka网络层看门小弟:ConnectionQuotas类
- 所在文件:core/src/main/scala/kafka/network/SocketServer.scala;
- 当某个IP到kafka的连接数过多时,将抛出
TooManyConnectionsException异常; - 实现就是通过加锁的加减计数;
SocketServer 图解:
SocketServer.png
