Apache Kafka源码分析 – Broker Server
1. Kafka.scala
在Kafka的main入口中startup KafkaServerStartable, 而KafkaServerStartable这是对KafkaServer的封装
1: val kafkaServerStartble = new KafkaServerStartable(serverConfig)
2: kafkaServerStartble.startup
1: package kafka.server
2: class KafkaServerStartable(val serverConfig: KafkaConfig) extends Logging {
3: private var server : KafkaServer = null
4:
5: private def init() {
6: server = new KafkaServer(serverConfig)
7: }
8:
9: def startup() {
10: try {
11: server.startup()
12: }
13: catch {...}
14: }
15: }
2. KafkaServer
KafkaServer代表一个kafka broker, 这是kafka的核心.
只需要看看里面startup了哪些modules, 就知道broker做了哪些工作, 后面一个个具体分析吧
1: package kafka.server
2: /**
3: * Represents the lifecycle of a single Kafka broker. Handles all functionality required
4: * to start up and shutdown a single Kafka node.
5: */
6: class KafkaServer(val config: KafkaConfig, time: Time = SystemTime) extends Logging {
7: var socketServer: SocketServer = null
8: var requestHandlerPool: KafkaRequestHandlerPool = null
9: var logManager: LogManager = null
10: var kafkaHealthcheck: KafkaHealthcheck = null
11: var topicConfigManager: TopicConfigManager = null
12: var replicaManager: ReplicaManager = null
13: var apis: KafkaApis = null
14: var kafkaController: KafkaController = null
15: val kafkaScheduler = new KafkaScheduler(config.backgroundThreads)
16: var zkClient: ZkClient = null
17:
18: /**
19: * Start up API for bringing up a single instance of the Kafka server.
20: * Instantiates the LogManager, the SocketServer and the request handlers - KafkaRequestHandlers
21: */
22: def startup() {
23: /* start scheduler */
24: kafkaScheduler.startup()
25:
26: /* setup zookeeper */
27: zkClient = initZk()
28:
29: /* start log manager */
30: logManager = createLogManager(zkClient)
31: logManager.startup()
32:
33: socketServer = new SocketServer(config.brokerId,
34: config.hostName,
35: config.port,
36: config.numNetworkThreads,
37: config.queuedMaxRequests,
38: config.socketSendBufferBytes,
39: config.socketReceiveBufferBytes,
40: config.socketRequestMaxBytes)
41: socketServer.startup()
42:
43: replicaManager = new ReplicaManager(config, time, zkClient, kafkaScheduler, logManager, isShuttingDown)
44: kafkaController = new KafkaController(config, zkClient)
45:
46: /* start processing requests */
47: apis = new KafkaApis(socketServer.requestChannel, replicaManager, zkClient, config.brokerId, config, kafkaController)
48: requestHandlerPool = new KafkaRequestHandlerPool(config.brokerId, socketServer.requestChannel, apis, config.numIoThreads)
49:
50: replicaManager.startup()
51:
52: kafkaController.startup()
53:
54: topicConfigManager = new TopicConfigManager(zkClient, logManager)
55: topicConfigManager.startup()
56:
57: /* tell everyone we are alive */
58: kafkaHealthcheck = new KafkaHealthcheck(config.brokerId, config.advertisedHostName, config.advertisedPort, config.zkSessionTimeoutMs, zkClient)
59: kafkaHealthcheck.startup()
60: }
2.1 KafkaScheduler
KafkaSchduler用于在后台执行一些任务，用ScheduledThreadPoolExecutor实现
1: package kafka.utils
2:
3: /**
4: * A scheduler based on java.util.concurrent.ScheduledThreadPoolExecutor
5: *
6: * It has a pool of kafka-scheduler- threads that do the actual work.
7: *
8: * @param threads The number of threads in the thread pool
9: * @param threadNamePrefix The name to use for scheduler threads. This prefix will have a number appended to it.
10: * @param daemon If true the scheduler threads will be "daemon" threads and will not block jvm shutdown.
11: */
12: @threadsafe
13: class KafkaScheduler(val threads: Int,
14: val threadNamePrefix: String = "kafka-scheduler-",
15: daemon: Boolean = true) extends Scheduler with Logging {
16: @volatile private var executor: ScheduledThreadPoolExecutor = null
17: override def startup() {
18: this synchronized {
19: executor = new ScheduledThreadPoolExecutor(threads) //创建ScheduledThreadPoolExecutor
20: executor.setContinueExistingPeriodicTasksAfterShutdownPolicy(false)
21: executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false)
22: executor.setThreadFactory(new ThreadFactory() {
23: def newThread(runnable: Runnable): Thread =
24: Utils.newThread(threadNamePrefix + schedulerThreadId.getAndIncrement(), runnable, daemon)
25: })
26: }
27: }
28:
29: def schedule(name: String, fun: ()=>Unit, delay: Long, period: Long, unit: TimeUnit) = {
30: val runnable = new Runnable { //将fun封装成Runnable
31: def run() = {
32: try {
33: fun()
34: } catch {...}
35: finally {...}
36: }
37: }
38: if(period >= 0) //在pool中进行delay schedule
39: executor.scheduleAtFixedRate(runnable, delay, period, unit)
40: else
41: executor.schedule(runnable, delay, unit)
42: }
2.2 Zookeeper Client
由于Kafka是基于zookeeper进行配置管理的， 所以需要创建zkclient和zookeeper集群通信
2.3 logManager
The entry point to the kafka log management subsystem. The log manager is responsible for log creation, retrieval, and cleaning.
Apache Kafka源码分析 – Log Management
2.4 ReplicaManager
在0.8中新加入的replica相关模块
Apache Kafka Replication Design – High level
kafka Detailed Replication Design V3
Apache Kafka源码分析 – Controller
Apache Kafka源码分析 – ReplicaManager
2.5 Kafka Socket Server
首先broker server是socket server，所有和broker的交互都是通过往socket端口发送request来实现的
socketServer = new SocketServer(config.brokerId...)
KafkaApis
该类封装了所有request的处理逻辑
KafkaRequestHandler