spark源码之sparkEnv(2)blockManager

1 sparkEnv中初始化blockManager

首先,根据是在驱动还是在executor上,选择端口。

   val blockManagerPort = if (isDriver) {
      conf.get(DRIVER_BLOCK_MANAGER_PORT)
    } else {
      conf.get(BLOCK_MANAGER_PORT)
    }

有了端口,就可以建立基于netty的rpc系统,传输大文件

    val blockTransferService =
      new NettyBlockTransferService(conf, securityManager, bindAddress, advertiseAddress,
        blockManagerPort, numUsableCores)

如果是在驱动程序,创建blockManagerMaster ,如果在executor上根据blockManagerMaster 和blockTransferService 创建blockManager。

    val blockManagerMaster = new BlockManagerMaster(registerOrLookupEndpoint(
      BlockManagerMaster.DRIVER_ENDPOINT_NAME,
      new BlockManagerMasterEndpoint(rpcEnv, isLocal, conf, listenerBus)),
      conf, isDriver)

    // NB: blockManager is not valid until initialize() is called later.
    val blockManager = new BlockManager(executorId, rpcEnv, blockManagerMaster,
      serializerManager, conf, memoryManager, mapOutputTracker, shuffleManager,
      blockTransferService, securityManager, numUsableCores)

在master上,registerOrLookupEndpoint构造一个BlockManagerMasterEndpoint,并将该点注册在rpcEnv中。

BlockManagerMasterEndpoint 负责通过rpc方式去管理所有节点的 BlockManager。

而在executor上创建manager时,会用setupEndpointRef 方法获取到了 BlockManagerMasterEndpoint的引用 BlockManagerMasterEndpointRef, 同时也会启动自己的 BlockManager。

这样就建立了基于rpc的分布式存储系统。

2 blockTransferService

由于分布式存储,block可能存放在不同的节点。如果需要传输这些block就需要建立通信。

private[spark] class NettyBlockTransferService(
    conf: SparkConf,
    securityManager: SecurityManager,
    bindAddress: String,
    override val hostName: String,
    _port: Int,
    numCores: Int)
  extends BlockTransferService {

  private val serializer = new JavaSerializer(conf)//序列化器
  private val authEnabled = securityManager.isAuthenticationEnabled()//安全管理
  private val transportConf = SparkTransportConf.fromSparkConf(conf, "shuffle", numCores)//配置参数,shuffle和核心个数

  private[this] var transportContext: TransportContext = _//管理网络I/O上下文
  private[this] var server: TransportServer = _
  private[this] var clientFactory: TransportClientFactory = _
  private[this] var appId: String = _
  //初始化网络服务器和客户端
  override def init(blockDataManager: BlockDataManager): Unit = {
    val rpcHandler = new NettyBlockRpcServer(conf.getAppId, serializer, blockDataManager)
    var serverBootstrap: Option[TransportServerBootstrap] = None
    var clientBootstrap: Option[TransportClientBootstrap] = None
    if (authEnabled) {
      serverBootstrap = Some(new AuthServerBootstrap(transportConf, securityManager))
      clientBootstrap = Some(new AuthClientBootstrap(transportConf, conf.getAppId, securityManager))
    }
    transportContext = new TransportContext(transportConf, rpcHandler)
    clientFactory = transportContext.createClientFactory(clientBootstrap.toSeq.asJava)
    server = createServer(serverBootstrap.toList)
    appId = conf.getAppId
    logInfo(s"Server created on ${hostName}:${server.getPort}")
  }

  /** 根据具体的地址建立server */
  private def createServer(bootstraps: List[TransportServerBootstrap]): TransportServer = {
    def startService(port: Int): (TransportServer, Int) = {
      val server = transportContext.createServer(bindAddress, port, bootstraps.asJava)
      (server, server.getPort)
    }

    Utils.startServiceOnPort(_port, startService, conf, getClass.getName)._1
  }

blockTransferService 的 fetchBlocks方法,会去其他真正存储节点上去fetch数据, 先获得一个client,然后调用OneForOneBlockFetcher获取block

  override def fetchBlocks(
      host: String,
      port: Int,
      execId: String,
      blockIds: Array[String],
      listener: BlockFetchingListener,
      shuffleFiles: Array[File]): Unit = {
    logTrace(s"Fetch blocks from $host:$port (executor id $execId)")
    try {
      val blockFetchStarter = new RetryingBlockFetcher.BlockFetchStarter {
        override def createAndStart(blockIds: Array[String], listener: BlockFetchingListener) {
          val client = clientFactory.createClient(host, port)
          new OneForOneBlockFetcher(client, appId, execId, blockIds.toArray, listener,
            transportConf, shuffleFiles).start()
        }
      }

      val maxRetries = transportConf.maxIORetries()
      if (maxRetries > 0) {
        // Note this Fetcher will correctly handle maxRetries == 0; we avoid it just in case there's
        // a bug in this code. We should remove the if statement once we're sure of the stability.
        new RetryingBlockFetcher(transportConf, blockFetchStarter, blockIds, listener).start()
      } else {
        blockFetchStarter.createAndStart(blockIds, listener)
      }
    } catch {
      case e: Exception =>
        logError("Exception while beginning fetchBlocks", e)
        blockIds.foreach(listener.onBlockFetchFailure(_, e))
    }
  }

  override def port: Int = server.getPort

3 BlockManagerMaster

在master上,registerOrLookupEndpoint构造一个BlockManagerMasterEndpoint,将该点注册在rpcEnv中。返回一个EndpointRef。

然后其他executor就可以在Master上注册blockManager,驱动端用driverEndpoint.askSync询问并接收这个注册信息。:

  def registerBlockManager(
      blockManagerId: BlockManagerId,
      maxOnHeapMemSize: Long,
      maxOffHeapMemSize: Long,
      slaveEndpoint: RpcEndpointRef): BlockManagerId = {
    logInfo(s"Registering BlockManager $blockManagerId")
    val updatedId = driverEndpoint.askSync[BlockManagerId](
      RegisterBlockManager(blockManagerId, maxOnHeapMemSize, maxOffHeapMemSize, slaveEndpoint))
    logInfo(s"Registered BlockManager $updatedId")
    updatedId
  }

除此之外,Master管理其他block

比如移除executor:

  def removeExecutor(execId: String) {
    tell(RemoveExecutor(execId))
    logInfo("Removed " + execId + " successfully in removeExecutor")
  }

从一个节点清除block,驱动必须知道Id

  def removeBlock(blockId: BlockId) {
    driverEndpoint.askSync[Boolean](RemoveBlock(blockId))
  }

清除所有属于同一个RDD的blocks

  def removeRdd(rddId: Int, blocking: Boolean) {
    val future = driverEndpoint.askSync[Future[Seq[Int]]](RemoveRdd(rddId))
    future.onFailure {
      case e: Exception =>
        logWarning(s"Failed to remove RDD $rddId - ${e.getMessage}", e)
    }(ThreadUtils.sameThread)
    if (blocking) {
      timeout.awaitResult(future)
    }
  }

……

4 BlockManager

建立一个SlaveEndpoint。

  private val slaveEndpoint = rpcEnv.setupEndpoint(
    "BlockManagerEndpoint" + BlockManager.ID_GENERATOR.next,
    new BlockManagerSlaveEndpoint(rpcEnv, this, mapOutputTracker))

加上blockmanagerId

  var blockManagerId: BlockManagerId = _

BlockManager的实例对象调用initializes的时候才能正常工作。
主要是BlockTransferService(网络通信),ShuffleClient的初始化

def initialize(appId: String): Unit = {
    blockTransferService.init(this)
    shuffleClient.init(appId)

    blockReplicationPolicy = {
      val priorityClass = conf.get(
        "spark.storage.replication.policy", classOf[RandomBlockReplicationPolicy].getName)
      val clazz = Utils.classForName(priorityClass)
      val ret = clazz.newInstance.asInstanceOf[BlockReplicationPolicy]
      logInfo(s"Using $priorityClass for block replication policy")
      ret
    }

    val id =
      BlockManagerId(executorId, blockTransferService.hostName, blockTransferService.port, None)

    val idFromMaster = master.registerBlockManager(
      id,
      maxOnHeapMemory,
      maxOffHeapMemory,
      slaveEndpoint)//向master注册slaveEndpoint

    blockManagerId = if (idFromMaster != null) idFromMaster else id

    shuffleServerId = if (externalShuffleServiceEnabled) {
      logInfo(s"external shuffle service port = $externalShuffleServicePort")
      BlockManagerId(executorId, blockTransferService.hostName, externalShuffleServicePort)
    } else {
      blockManagerId
    }

    // Register Executors' configuration with the local shuffle service, if one should exist.
    if (externalShuffleServiceEnabled && !blockManagerId.isDriver) {
      registerWithExternalShuffleServer()
    }

    logInfo(s"Initialized BlockManager: $blockManagerId")
  }

blockstore

block的存储分为两个层次:

  private[spark] val memoryStore =
    new MemoryStore(conf, blockInfoManager, serializerManager, memoryManager, this)
  private[spark] val diskStore = new DiskStore(conf, diskBlockManager, securityManager)
  memoryManager.setMemoryStore(memoryStore)

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