spark BlockManager 源码

  • 2022-10-20
  • 浏览 (195)

spark BlockManager 代码

文件路径:/core/src/main/scala/org/apache/spark/storage/BlockManager.scala

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.spark.storage

import java.io._
import java.lang.ref.{ReferenceQueue => JReferenceQueue, WeakReference}
import java.nio.ByteBuffer
import java.nio.channels.Channels
import java.util.Collections
import java.util.concurrent.{CompletableFuture, ConcurrentHashMap, TimeUnit}

import scala.collection.JavaConverters._
import scala.collection.mutable
import scala.collection.mutable.HashMap
import scala.concurrent.{ExecutionContext, Future}
import scala.concurrent.duration._
import scala.reflect.ClassTag
import scala.util.{Failure, Random, Success, Try}
import scala.util.control.NonFatal

import com.codahale.metrics.{MetricRegistry, MetricSet}
import com.esotericsoftware.kryo.KryoException
import com.google.common.cache.CacheBuilder
import org.apache.commons.io.IOUtils

import org.apache.spark._
import org.apache.spark.errors.SparkCoreErrors
import org.apache.spark.executor.DataReadMethod
import org.apache.spark.internal.Logging
import org.apache.spark.internal.config
import org.apache.spark.internal.config.Network
import org.apache.spark.memory.{MemoryManager, MemoryMode}
import org.apache.spark.metrics.source.Source
import org.apache.spark.network._
import org.apache.spark.network.buffer.{FileSegmentManagedBuffer, ManagedBuffer}
import org.apache.spark.network.client.StreamCallbackWithID
import org.apache.spark.network.netty.SparkTransportConf
import org.apache.spark.network.shuffle._
import org.apache.spark.network.shuffle.checksum.{Cause, ShuffleChecksumHelper}
import org.apache.spark.network.shuffle.protocol.ExecutorShuffleInfo
import org.apache.spark.network.util.TransportConf
import org.apache.spark.rpc.RpcEnv
import org.apache.spark.scheduler.ExecutorCacheTaskLocation
import org.apache.spark.serializer.{SerializerInstance, SerializerManager}
import org.apache.spark.shuffle.{IndexShuffleBlockResolver, MigratableResolver, ShuffleManager, ShuffleWriteMetricsReporter}
import org.apache.spark.storage.BlockManagerMessages.{DecommissionBlockManager, ReplicateBlock}
import org.apache.spark.storage.memory._
import org.apache.spark.unsafe.Platform
import org.apache.spark.util._
import org.apache.spark.util.io.ChunkedByteBuffer

/* Class for returning a fetched block and associated metrics. */
private[spark] class BlockResult(
    val data: Iterator[Any],
    val readMethod: DataReadMethod.Value,
    val bytes: Long)

/**
 * Abstracts away how blocks are stored and provides different ways to read the underlying block
 * data. Callers should call [[dispose()]] when they're done with the block.
 */
private[spark] trait BlockData {

  def toInputStream(): InputStream

  /**
   * Returns a Netty-friendly wrapper for the block's data.
   *
   * Please see `ManagedBuffer.convertToNetty()` for more details.
   */
  def toNetty(): Object

  def toChunkedByteBuffer(allocator: Int => ByteBuffer): ChunkedByteBuffer

  def toByteBuffer(): ByteBuffer

  def size: Long

  def dispose(): Unit

}

private[spark] class ByteBufferBlockData(
    val buffer: ChunkedByteBuffer,
    val shouldDispose: Boolean) extends BlockData {

  override def toInputStream(): InputStream = buffer.toInputStream(dispose = false)

  override def toNetty(): Object = buffer.toNetty

  override def toChunkedByteBuffer(allocator: Int => ByteBuffer): ChunkedByteBuffer = {
    buffer.copy(allocator)
  }

  override def toByteBuffer(): ByteBuffer = buffer.toByteBuffer

  override def size: Long = buffer.size

  override def dispose(): Unit = {
    if (shouldDispose) {
      buffer.dispose()
    }
  }

}

private[spark] class HostLocalDirManager(
    futureExecutionContext: ExecutionContext,
    cacheSize: Int,
    blockStoreClient: BlockStoreClient) extends Logging {

  private val executorIdToLocalDirsCache =
    CacheBuilder
      .newBuilder()
      .maximumSize(cacheSize)
      .build[String, Array[String]]()

  private[spark] def getCachedHostLocalDirs: Map[String, Array[String]] =
    executorIdToLocalDirsCache.synchronized {
      executorIdToLocalDirsCache.asMap().asScala.toMap
    }

  private[spark] def getCachedHostLocalDirsFor(executorId: String): Option[Array[String]] =
    executorIdToLocalDirsCache.synchronized {
      Option(executorIdToLocalDirsCache.getIfPresent(executorId))
    }

  private[spark] def getHostLocalDirs(
      host: String,
      port: Int,
      executorIds: Array[String])(
      callback: Try[Map[String, Array[String]]] => Unit): Unit = {
    val hostLocalDirsCompletable = new CompletableFuture[java.util.Map[String, Array[String]]]
    blockStoreClient.getHostLocalDirs(
      host,
      port,
      executorIds,
      hostLocalDirsCompletable)
    hostLocalDirsCompletable.whenComplete { (hostLocalDirs, throwable) =>
      if (hostLocalDirs != null) {
        callback(Success(hostLocalDirs.asScala.toMap))
        executorIdToLocalDirsCache.synchronized {
          executorIdToLocalDirsCache.putAll(hostLocalDirs)
        }
      } else {
        callback(Failure(throwable))
      }
    }
  }
}

/**
 * Manager running on every node (driver and executors) which provides interfaces for putting and
 * retrieving blocks both locally and remotely into various stores (memory, disk, and off-heap).
 *
 * Note that [[initialize()]] must be called before the BlockManager is usable.
 */
private[spark] class BlockManager(
    val executorId: String,
    rpcEnv: RpcEnv,
    val master: BlockManagerMaster,
    val serializerManager: SerializerManager,
    val conf: SparkConf,
    memoryManager: MemoryManager,
    mapOutputTracker: MapOutputTracker,
    shuffleManager: ShuffleManager,
    val blockTransferService: BlockTransferService,
    securityManager: SecurityManager,
    externalBlockStoreClient: Option[ExternalBlockStoreClient])
  extends BlockDataManager with BlockEvictionHandler with Logging {

  // same as `conf.get(config.SHUFFLE_SERVICE_ENABLED)`
  private[spark] val externalShuffleServiceEnabled: Boolean = externalBlockStoreClient.isDefined
  private val isDriver = executorId == SparkContext.DRIVER_IDENTIFIER

  private val remoteReadNioBufferConversion =
    conf.get(Network.NETWORK_REMOTE_READ_NIO_BUFFER_CONVERSION)

  private[spark] val subDirsPerLocalDir = conf.get(config.DISKSTORE_SUB_DIRECTORIES)

  val diskBlockManager = {
    // Only perform cleanup if an external service is not serving our shuffle files.
    val deleteFilesOnStop =
      !externalShuffleServiceEnabled || isDriver
    new DiskBlockManager(conf, deleteFilesOnStop = deleteFilesOnStop, isDriver = isDriver)
  }

  // Visible for testing
  private[storage] val blockInfoManager = new BlockInfoManager

  private val futureExecutionContext = ExecutionContext.fromExecutorService(
    ThreadUtils.newDaemonCachedThreadPool("block-manager-future", 128))

  // Actual storage of where blocks are kept
  private[spark] val memoryStore =
    new MemoryStore(conf, blockInfoManager, serializerManager, memoryManager, this)
  private[spark] val diskStore = new DiskStore(conf, diskBlockManager, securityManager)
  memoryManager.setMemoryStore(memoryStore)

  // Note: depending on the memory manager, `maxMemory` may actually vary over time.
  // However, since we use this only for reporting and logging, what we actually want here is
  // the absolute maximum value that `maxMemory` can ever possibly reach. We may need
  // to revisit whether reporting this value as the "max" is intuitive to the user.
  private val maxOnHeapMemory = memoryManager.maxOnHeapStorageMemory
  private val maxOffHeapMemory = memoryManager.maxOffHeapStorageMemory

  private[spark] val externalShuffleServicePort = StorageUtils.externalShuffleServicePort(conf)

  var blockManagerId: BlockManagerId = _

  // Address of the server that serves this executor's shuffle files. This is either an external
  // service, or just our own Executor's BlockManager.
  private[spark] var shuffleServerId: BlockManagerId = _

  // Client to read other executors' blocks. This is either an external service, or just the
  // standard BlockTransferService to directly connect to other Executors.
  private[spark] val blockStoreClient = externalBlockStoreClient.getOrElse(blockTransferService)

  // Max number of failures before this block manager refreshes the block locations from the driver
  private val maxFailuresBeforeLocationRefresh =
    conf.get(config.BLOCK_FAILURES_BEFORE_LOCATION_REFRESH)

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

  // Pending re-registration action being executed asynchronously or null if none is pending.
  // Accesses should synchronize on asyncReregisterLock.
  private var asyncReregisterTask: Future[Unit] = null
  private val asyncReregisterLock = new Object

  // Field related to peer block managers that are necessary for block replication
  @volatile private var cachedPeers: Seq[BlockManagerId] = _
  private val peerFetchLock = new Object
  private var lastPeerFetchTimeNs = 0L

  private var blockReplicationPolicy: BlockReplicationPolicy = _

  // visible for test
  // This is volatile since if it's defined we should not accept remote blocks.
  @volatile private[spark] var decommissioner: Option[BlockManagerDecommissioner] = None

  // A DownloadFileManager used to track all the files of remote blocks which are above the
  // specified memory threshold. Files will be deleted automatically based on weak reference.
  // Exposed for test
  private[storage] val remoteBlockTempFileManager =
    new BlockManager.RemoteBlockDownloadFileManager(
      this,
      securityManager.getIOEncryptionKey())
  private val maxRemoteBlockToMem = conf.get(config.MAX_REMOTE_BLOCK_SIZE_FETCH_TO_MEM)

  var hostLocalDirManager: Option[HostLocalDirManager] = None

  @inline final private def isDecommissioning() = {
    decommissioner.isDefined
  }

  @inline final private def checkShouldStore(blockId: BlockId) = {
    // Don't reject broadcast blocks since they may be stored during task exec and
    // don't need to be migrated.
    if (isDecommissioning() && !blockId.isBroadcast) {
      throw SparkCoreErrors.cannotSaveBlockOnDecommissionedExecutorError(blockId)
    }
  }

  // This is a lazy val so someone can migrating RDDs even if they don't have a MigratableResolver
  // for shuffles. Used in BlockManagerDecommissioner & block puts.
  private[storage] lazy val migratableResolver: MigratableResolver = {
    shuffleManager.shuffleBlockResolver.asInstanceOf[MigratableResolver]
  }

  override def getLocalDiskDirs: Array[String] = diskBlockManager.localDirsString

  /**
   * Diagnose the possible cause of the shuffle data corruption by verifying the shuffle checksums
   *
   * @param blockId The blockId of the corrupted shuffle block
   * @param checksumByReader The checksum value of the corrupted block
   * @param algorithm The cheksum algorithm that is used when calculating the checksum value
   */
  override def diagnoseShuffleBlockCorruption(
      blockId: BlockId,
      checksumByReader: Long,
      algorithm: String): Cause = {
    assert(blockId.isInstanceOf[ShuffleBlockId],
      s"Corruption diagnosis only supports shuffle block yet, but got $blockId")
    val shuffleBlock = blockId.asInstanceOf[ShuffleBlockId]
    val resolver = shuffleManager.shuffleBlockResolver.asInstanceOf[IndexShuffleBlockResolver]
    val checksumFile =
      resolver.getChecksumFile(shuffleBlock.shuffleId, shuffleBlock.mapId, algorithm)
    val reduceId = shuffleBlock.reduceId
    ShuffleChecksumHelper.diagnoseCorruption(
      algorithm, checksumFile, reduceId, resolver.getBlockData(shuffleBlock), checksumByReader)
  }

  /**
   * Abstraction for storing blocks from bytes, whether they start in memory or on disk.
   *
   * @param blockSize the decrypted size of the block
   */
  private[spark] abstract class BlockStoreUpdater[T](
      blockSize: Long,
      blockId: BlockId,
      level: StorageLevel,
      classTag: ClassTag[T],
      tellMaster: Boolean,
      keepReadLock: Boolean) {

    /**
     *  Reads the block content into the memory. If the update of the block store is based on a
     *  temporary file this could lead to loading the whole file into a ChunkedByteBuffer.
     */
    protected def readToByteBuffer(): ChunkedByteBuffer

    protected def blockData(): BlockData

    protected def saveToDiskStore(): Unit

    private def saveDeserializedValuesToMemoryStore(inputStream: InputStream): Boolean = {
      try {
        val values = serializerManager.dataDeserializeStream(blockId, inputStream)(classTag)
        memoryStore.putIteratorAsValues(blockId, values, level.memoryMode, classTag) match {
          case Right(_) => true
          case Left(iter) =>
            // If putting deserialized values in memory failed, we will put the bytes directly
            // to disk, so we don't need this iterator and can close it to free resources
            // earlier.
            iter.close()
            false
        }
      } catch {
        case ex: KryoException if ex.getCause.isInstanceOf[IOException] =>
          logInfo(extendMessageWithBlockDetails(ex.getMessage, blockId))
          throw ex
      } finally {
        IOUtils.closeQuietly(inputStream)
      }
    }

    private def saveSerializedValuesToMemoryStore(bytes: ChunkedByteBuffer): Boolean = {
      val memoryMode = level.memoryMode
      memoryStore.putBytes(blockId, blockSize, memoryMode, () => {
        if (memoryMode == MemoryMode.OFF_HEAP && bytes.chunks.exists(!_.isDirect)) {
          bytes.copy(Platform.allocateDirectBuffer)
        } else {
          bytes
        }
      })
    }

    /**
     * Put the given data according to the given level in one of the block stores, replicating
     * the values if necessary.
     *
     * If the block already exists, this method will not overwrite it.
     *
     * If keepReadLock is true, this method will hold the read lock when it returns (even if the
     * block already exists). If false, this method will hold no locks when it returns.
     *
     * @return true if the block was already present or if the put succeeded, false otherwise.
     */
     def save(): Boolean = {
      doPut(blockId, level, classTag, tellMaster, keepReadLock) { info =>
        val startTimeNs = System.nanoTime()

        // Since we're storing bytes, initiate the replication before storing them locally.
        // This is faster as data is already serialized and ready to send.
        val replicationFuture = if (level.replication > 1) {
          Future {
            // This is a blocking action and should run in futureExecutionContext which is a cached
            // thread pool.
            replicate(blockId, blockData(), level, classTag)
          }(futureExecutionContext)
        } else {
          null
        }
        if (level.useMemory) {
          // Put it in memory first, even if it also has useDisk set to true;
          // We will drop it to disk later if the memory store can't hold it.
          val putSucceeded = if (level.deserialized) {
            saveDeserializedValuesToMemoryStore(blockData().toInputStream())
          } else {
            saveSerializedValuesToMemoryStore(readToByteBuffer())
          }
          if (!putSucceeded && level.useDisk) {
            logWarning(s"Persisting block $blockId to disk instead.")
            saveToDiskStore()
          }
        } else if (level.useDisk) {
          saveToDiskStore()
        }
        val putBlockStatus = getCurrentBlockStatus(blockId, info)
        val blockWasSuccessfullyStored = putBlockStatus.storageLevel.isValid
        if (blockWasSuccessfullyStored) {
          // Now that the block is in either the memory or disk store,
          // tell the master about it.
          info.size = blockSize
          if (tellMaster && info.tellMaster) {
            reportBlockStatus(blockId, putBlockStatus)
          }
          addUpdatedBlockStatusToTaskMetrics(blockId, putBlockStatus)
        }
        logDebug(s"Put block ${blockId} locally took ${Utils.getUsedTimeNs(startTimeNs)}")
        if (level.replication > 1) {
          // Wait for asynchronous replication to finish
          try {
            ThreadUtils.awaitReady(replicationFuture, Duration.Inf)
          } catch {
            case NonFatal(t) => throw SparkCoreErrors.waitingForReplicationToFinishError(t)
          }
        }
        if (blockWasSuccessfullyStored) {
          None
        } else {
          Some(blockSize)
        }
      }.isEmpty
    }
  }

  /**
   * Helper for storing a block from bytes already in memory.
   * '''Important!''' Callers must not mutate or release the data buffer underlying `bytes`. Doing
   * so may corrupt or change the data stored by the `BlockManager`.
   */
  private case class ByteBufferBlockStoreUpdater[T](
      blockId: BlockId,
      level: StorageLevel,
      classTag: ClassTag[T],
      bytes: ChunkedByteBuffer,
      tellMaster: Boolean = true,
      keepReadLock: Boolean = false)
    extends BlockStoreUpdater[T](bytes.size, blockId, level, classTag, tellMaster, keepReadLock) {

    override def readToByteBuffer(): ChunkedByteBuffer = bytes

    /**
     * The ByteBufferBlockData wrapper is not disposed of to avoid releasing buffers that are
     * owned by the caller.
     */
    override def blockData(): BlockData = new ByteBufferBlockData(bytes, false)

    override def saveToDiskStore(): Unit = diskStore.putBytes(blockId, bytes)

  }

  /**
   * Helper for storing a block based from bytes already in a local temp file.
   */
  private[spark] case class TempFileBasedBlockStoreUpdater[T](
      blockId: BlockId,
      level: StorageLevel,
      classTag: ClassTag[T],
      tmpFile: File,
      blockSize: Long,
      tellMaster: Boolean = true,
      keepReadLock: Boolean = false)
    extends BlockStoreUpdater[T](blockSize, blockId, level, classTag, tellMaster, keepReadLock) {

    override def readToByteBuffer(): ChunkedByteBuffer = {
      val allocator = level.memoryMode match {
        case MemoryMode.ON_HEAP => ByteBuffer.allocate _
        case MemoryMode.OFF_HEAP => Platform.allocateDirectBuffer _
      }
      blockData().toChunkedByteBuffer(allocator)
    }

    override def blockData(): BlockData = diskStore.getBytes(tmpFile, blockSize)

    override def saveToDiskStore(): Unit = diskStore.moveFileToBlock(tmpFile, blockSize, blockId)

    override def save(): Boolean = {
      val res = super.save()
      tmpFile.delete()
      res
    }

  }

  /**
   * Initializes the BlockManager with the given appId. This is not performed in the constructor as
   * the appId may not be known at BlockManager instantiation time (in particular for the driver,
   * where it is only learned after registration with the TaskScheduler).
   *
   * This method initializes the BlockTransferService and BlockStoreClient, registers with the
   * BlockManagerMaster, starts the BlockManagerWorker endpoint, and registers with a local shuffle
   * service if configured.
   */
  def initialize(appId: String): Unit = {
    blockTransferService.init(this)
    externalBlockStoreClient.foreach { blockStoreClient =>
      blockStoreClient.init(appId)
    }
    blockReplicationPolicy = {
      val priorityClass = conf.get(config.STORAGE_REPLICATION_POLICY)
      val clazz = Utils.classForName(priorityClass)
      val ret = clazz.getConstructor().newInstance().asInstanceOf[BlockReplicationPolicy]
      logInfo(s"Using $priorityClass for block replication policy")
      ret
    }

    // Register Executors' configuration with the local shuffle service, if one should exist.
    // Registration with the ESS should happen before registering the block manager with the
    // BlockManagerMaster. In push-based shuffle, the registered BM is selected by the driver
    // as a merger. However, for the ESS on this host to be able to merge blocks successfully,
    // it needs the merge directories metadata which is provided by the local executor during
    // the registration with the ESS. Therefore, this registration should be prior to
    // the BlockManager registration. See SPARK-39647.
    if (externalShuffleServiceEnabled) {
      logInfo(s"external shuffle service port = $externalShuffleServicePort")
      shuffleServerId = BlockManagerId(executorId, blockTransferService.hostName,
        externalShuffleServicePort)
      if (!isDriver) {
        registerWithExternalShuffleServer()
      }
    }

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

    // The idFromMaster has just additional topology information. Otherwise, it has the same
    // executor id/host/port of idWithoutTopologyInfo which is not expected to be changed.
    val idFromMaster = master.registerBlockManager(
      id,
      diskBlockManager.localDirsString,
      maxOnHeapMemory,
      maxOffHeapMemory,
      storageEndpoint)

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

    if (!externalShuffleServiceEnabled) {
      shuffleServerId = blockManagerId
    }

    hostLocalDirManager = {
      if ((conf.get(config.SHUFFLE_HOST_LOCAL_DISK_READING_ENABLED) &&
          !conf.get(config.SHUFFLE_USE_OLD_FETCH_PROTOCOL)) ||
          Utils.isPushBasedShuffleEnabled(conf, isDriver)) {
        Some(new HostLocalDirManager(
          futureExecutionContext,
          conf.get(config.STORAGE_LOCAL_DISK_BY_EXECUTORS_CACHE_SIZE),
          blockStoreClient))
      } else {
        None
      }
    }

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

  def shuffleMetricsSource: Source = {
    import BlockManager._

    if (externalShuffleServiceEnabled) {
      new ShuffleMetricsSource("ExternalShuffle", blockStoreClient.shuffleMetrics())
    } else {
      new ShuffleMetricsSource("NettyBlockTransfer", blockStoreClient.shuffleMetrics())
    }
  }

  private def registerWithExternalShuffleServer(): Unit = {
    logInfo("Registering executor with local external shuffle service.")
    val shuffleManagerMeta =
      if (Utils.isPushBasedShuffleEnabled(conf, isDriver = isDriver, checkSerializer = false)) {
        s"${shuffleManager.getClass.getName}:" +
          s"${diskBlockManager.getMergeDirectoryAndAttemptIDJsonString()}}}"
      } else {
        shuffleManager.getClass.getName
      }
    val shuffleConfig = new ExecutorShuffleInfo(
      diskBlockManager.localDirsString,
      diskBlockManager.subDirsPerLocalDir,
      shuffleManagerMeta)

    val MAX_ATTEMPTS = conf.get(config.SHUFFLE_REGISTRATION_MAX_ATTEMPTS)
    val SLEEP_TIME_SECS = 5

    for (i <- 1 to MAX_ATTEMPTS) {
      try {
        // Synchronous and will throw an exception if we cannot connect.
        blockStoreClient.asInstanceOf[ExternalBlockStoreClient].registerWithShuffleServer(
          shuffleServerId.host, shuffleServerId.port, shuffleServerId.executorId, shuffleConfig)
        return
      } catch {
        case e: Exception if i < MAX_ATTEMPTS =>
          logError(s"Failed to connect to external shuffle server, will retry ${MAX_ATTEMPTS - i}"
            + s" more times after waiting $SLEEP_TIME_SECS seconds...", e)
          Thread.sleep(SLEEP_TIME_SECS * 1000L)
        case NonFatal(e) => throw SparkCoreErrors.unableToRegisterWithExternalShuffleServerError(e)
      }
    }
  }

  /**
   * Report all blocks to the BlockManager again. This may be necessary if we are dropped
   * by the BlockManager and come back or if we become capable of recovering blocks on disk after
   * an executor crash.
   *
   * This function deliberately fails silently if the master returns false (indicating that
   * the storage endpoint needs to re-register). The error condition will be detected again by the
   * next heart beat attempt or new block registration and another try to re-register all blocks
   * will be made then.
   */
  private def reportAllBlocks(): Unit = {
    logInfo(s"Reporting ${blockInfoManager.size} blocks to the master.")
    for ((blockId, info) <- blockInfoManager.entries) {
      val status = getCurrentBlockStatus(blockId, info)
      if (info.tellMaster && !tryToReportBlockStatus(blockId, status)) {
        logError(s"Failed to report $blockId to master; giving up.")
        return
      }
    }
  }

  /**
   * Re-register with the master and report all blocks to it. This will be called by the heart beat
   * thread if our heartbeat to the block manager indicates that we were not registered.
   *
   * Note that this method must be called without any BlockInfo locks held.
   */
  def reregister(): Unit = {
    // TODO: We might need to rate limit re-registering.
    logInfo(s"BlockManager $blockManagerId re-registering with master")
    master.registerBlockManager(blockManagerId, diskBlockManager.localDirsString, maxOnHeapMemory,
      maxOffHeapMemory, storageEndpoint)
    reportAllBlocks()
  }

  /**
   * Re-register with the master sometime soon.
   */
  private def asyncReregister(): Unit = {
    asyncReregisterLock.synchronized {
      if (asyncReregisterTask == null) {
        asyncReregisterTask = Future[Unit] {
          // This is a blocking action and should run in futureExecutionContext which is a cached
          // thread pool
          reregister()
          asyncReregisterLock.synchronized {
            asyncReregisterTask = null
          }
        }(futureExecutionContext)
      }
    }
  }

  /**
   * For testing. Wait for any pending asynchronous re-registration; otherwise, do nothing.
   */
  def waitForAsyncReregister(): Unit = {
    val task = asyncReregisterTask
    if (task != null) {
      try {
        ThreadUtils.awaitReady(task, Duration.Inf)
      } catch {
        case NonFatal(t) =>
          throw SparkCoreErrors.waitingForAsyncReregistrationError(t)
      }
    }
  }

  override def getHostLocalShuffleData(
      blockId: BlockId,
      dirs: Array[String]): ManagedBuffer = {
    shuffleManager.shuffleBlockResolver.getBlockData(blockId, Some(dirs))
  }

  /**
   * Interface to get local block data. Throws an exception if the block cannot be found or
   * cannot be read successfully.
   */
  override def getLocalBlockData(blockId: BlockId): ManagedBuffer = {
    if (blockId.isShuffle) {
      logDebug(s"Getting local shuffle block ${blockId}")
      try {
        shuffleManager.shuffleBlockResolver.getBlockData(blockId)
      } catch {
        case e: IOException =>
          if (conf.get(config.STORAGE_DECOMMISSION_FALLBACK_STORAGE_PATH).isDefined) {
            FallbackStorage.read(conf, blockId)
          } else {
            throw e
          }
      }
    } else {
      getLocalBytes(blockId) match {
        case Some(blockData) =>
          new BlockManagerManagedBuffer(blockInfoManager, blockId, blockData, true)
        case None =>
          // If this block manager receives a request for a block that it doesn't have then it's
          // likely that the master has outdated block statuses for this block. Therefore, we send
          // an RPC so that this block is marked as being unavailable from this block manager.
          reportBlockStatus(blockId, BlockStatus.empty)
          throw SparkCoreErrors.blockNotFoundError(blockId)
      }
    }
  }

  /**
   * Put the block locally, using the given storage level.
   *
   * '''Important!''' Callers must not mutate or release the data buffer underlying `bytes`. Doing
   * so may corrupt or change the data stored by the `BlockManager`.
   */
  override def putBlockData(
      blockId: BlockId,
      data: ManagedBuffer,
      level: StorageLevel,
      classTag: ClassTag[_]): Boolean = {
    putBytes(blockId, new ChunkedByteBuffer(data.nioByteBuffer()), level)(classTag)
  }

  override def putBlockDataAsStream(
      blockId: BlockId,
      level: StorageLevel,
      classTag: ClassTag[_]): StreamCallbackWithID = {

    checkShouldStore(blockId)

    if (blockId.isShuffle) {
      logDebug(s"Putting shuffle block ${blockId}")
      try {
        return migratableResolver.putShuffleBlockAsStream(blockId, serializerManager)
      } catch {
        case e: ClassCastException =>
          throw SparkCoreErrors.unexpectedShuffleBlockWithUnsupportedResolverError(shuffleManager,
            blockId)
      }
    }
    logDebug(s"Putting regular block ${blockId}")
    // All other blocks
    val (_, tmpFile) = diskBlockManager.createTempLocalBlock()
    val channel = new CountingWritableChannel(
      Channels.newChannel(serializerManager.wrapForEncryption(new FileOutputStream(tmpFile))))
    logTrace(s"Streaming block $blockId to tmp file $tmpFile")
    new StreamCallbackWithID {

      override def getID: String = blockId.name

      override def onData(streamId: String, buf: ByteBuffer): Unit = {
        while (buf.hasRemaining) {
          channel.write(buf)
        }
      }

      override def onComplete(streamId: String): Unit = {
        logTrace(s"Done receiving block $blockId, now putting into local blockManager")
        // Note this is all happening inside the netty thread as soon as it reads the end of the
        // stream.
        channel.close()
        val blockSize = channel.getCount
        val blockStored = TempFileBasedBlockStoreUpdater(
          blockId, level, classTag, tmpFile, blockSize).save()
        if (!blockStored) {
          throw SparkCoreErrors.failToStoreBlockOnBlockManagerError(blockManagerId, blockId)
        }
      }

      override def onFailure(streamId: String, cause: Throwable): Unit = {
        // the framework handles the connection itself, we just need to do local cleanup
        channel.close()
        tmpFile.delete()
      }
    }
  }

  /**
   * Get the local merged shuffle block data for the given block ID as multiple chunks.
   * A merged shuffle file is divided into multiple chunks according to the index file.
   * Instead of reading the entire file as a single block, we split it into smaller chunks
   * which will be memory efficient when performing certain operations.
   */
  def getLocalMergedBlockData(
      blockId: ShuffleMergedBlockId,
      dirs: Array[String]): Seq[ManagedBuffer] = {
    shuffleManager.shuffleBlockResolver.getMergedBlockData(blockId, Some(dirs))
  }

  /**
   * Get the local merged shuffle block meta data for the given block ID.
   */
  def getLocalMergedBlockMeta(
      blockId: ShuffleMergedBlockId,
      dirs: Array[String]): MergedBlockMeta = {
    shuffleManager.shuffleBlockResolver.getMergedBlockMeta(blockId, Some(dirs))
  }

  /**
   * Get the BlockStatus for the block identified by the given ID, if it exists.
   * NOTE: This is mainly for testing.
   */
  def getStatus(blockId: BlockId): Option[BlockStatus] = {
    blockInfoManager.get(blockId).map { info =>
      val memSize = if (memoryStore.contains(blockId)) memoryStore.getSize(blockId) else 0L
      val diskSize = if (diskStore.contains(blockId)) diskStore.getSize(blockId) else 0L
      BlockStatus(info.level, memSize = memSize, diskSize = diskSize)
    }
  }

  /**
   * Get the ids of existing blocks that match the given filter. Note that this will
   * query the blocks stored in the disk block manager (that the block manager
   * may not know of).
   */
  def getMatchingBlockIds(filter: BlockId => Boolean): Seq[BlockId] = {
    // The `toArray` is necessary here in order to force the list to be materialized so that we
    // don't try to serialize a lazy iterator when responding to client requests.
    (blockInfoManager.entries.map(_._1) ++ diskBlockManager.getAllBlocks())
      .filter(filter)
      .toArray
      .toSeq
  }

  /**
   * Tell the master about the current storage status of a block. This will send a block update
   * message reflecting the current status, *not* the desired storage level in its block info.
   * For example, a block with MEMORY_AND_DISK set might have fallen out to be only on disk.
   *
   * droppedMemorySize exists to account for when the block is dropped from memory to disk (so
   * it is still valid). This ensures that update in master will compensate for the increase in
   * memory on the storage endpoint.
   */
  private[spark] def reportBlockStatus(
      blockId: BlockId,
      status: BlockStatus,
      droppedMemorySize: Long = 0L): Unit = {
    val needReregister = !tryToReportBlockStatus(blockId, status, droppedMemorySize)
    if (needReregister) {
      logInfo(s"Got told to re-register updating block $blockId")
      // Re-registering will report our new block for free.
      asyncReregister()
    }
    logDebug(s"Told master about block $blockId")
  }

  /**
   * Actually send a UpdateBlockInfo message. Returns the master's response,
   * which will be true if the block was successfully recorded and false if
   * the storage endpoint needs to re-register.
   */
  private def tryToReportBlockStatus(
      blockId: BlockId,
      status: BlockStatus,
      droppedMemorySize: Long = 0L): Boolean = {
    val storageLevel = status.storageLevel
    val inMemSize = Math.max(status.memSize, droppedMemorySize)
    val onDiskSize = status.diskSize
    master.updateBlockInfo(blockManagerId, blockId, storageLevel, inMemSize, onDiskSize)
  }

  /**
   * Return the updated storage status of the block with the given ID. More specifically, if
   * the block is dropped from memory and possibly added to disk, return the new storage level
   * and the updated in-memory and on-disk sizes.
   */
  private def getCurrentBlockStatus(blockId: BlockId, info: BlockInfo): BlockStatus = {
    info.synchronized {
      info.level match {
        case null =>
          BlockStatus.empty
        case level =>
          val inMem = level.useMemory && memoryStore.contains(blockId)
          val onDisk = level.useDisk && diskStore.contains(blockId)
          val deserialized = if (inMem) level.deserialized else false
          val replication = if (inMem  || onDisk) level.replication else 1
          val storageLevel = StorageLevel(
            useDisk = onDisk,
            useMemory = inMem,
            useOffHeap = level.useOffHeap,
            deserialized = deserialized,
            replication = replication)
          val memSize = if (inMem) memoryStore.getSize(blockId) else 0L
          val diskSize = if (onDisk) diskStore.getSize(blockId) else 0L
          BlockStatus(storageLevel, memSize, diskSize)
      }
    }
  }

  /**
   * Get locations of an array of blocks.
   */
  private def getLocationBlockIds(blockIds: Array[BlockId]): Array[Seq[BlockManagerId]] = {
    val startTimeNs = System.nanoTime()
    val locations = master.getLocations(blockIds).toArray
    logDebug(s"Got multiple block location in ${Utils.getUsedTimeNs(startTimeNs)}")
    locations
  }

  /**
   * Cleanup code run in response to a failed local read.
   * Must be called while holding a read lock on the block.
   */
  private def handleLocalReadFailure(blockId: BlockId): Nothing = {
    releaseLock(blockId)
    // Remove the missing block so that its unavailability is reported to the driver
    removeBlock(blockId)
    throw SparkCoreErrors.readLockedBlockNotFoundError(blockId)
  }

  private def isIORelatedException(t: Throwable): Boolean =
    t.isInstanceOf[IOException] ||
      (t.isInstanceOf[KryoException] && t.getCause.isInstanceOf[IOException])

  /**
   * Get block from local block manager as an iterator of Java objects.
   */
  def getLocalValues(blockId: BlockId): Option[BlockResult] = {
    logDebug(s"Getting local block $blockId")
    blockInfoManager.lockForReading(blockId) match {
      case None =>
        logDebug(s"Block $blockId was not found")
        None
      case Some(info) =>
        val level = info.level
        logDebug(s"Level for block $blockId is $level")
        val taskContext = Option(TaskContext.get())
        if (level.useMemory && memoryStore.contains(blockId)) {
          val iter: Iterator[Any] = if (level.deserialized) {
            memoryStore.getValues(blockId).get
          } else {
            serializerManager.dataDeserializeStream(
              blockId, memoryStore.getBytes(blockId).get.toInputStream())(info.classTag)
          }
          // We need to capture the current taskId in case the iterator completion is triggered
          // from a different thread which does not have TaskContext set; see SPARK-18406 for
          // discussion.
          val ci = CompletionIterator[Any, Iterator[Any]](iter, {
            releaseLock(blockId, taskContext)
          })
          Some(new BlockResult(ci, DataReadMethod.Memory, info.size))
        } else if (level.useDisk && diskStore.contains(blockId)) {
          var diskData: BlockData = null
          try {
            diskData = diskStore.getBytes(blockId)
            val iterToReturn = if (level.deserialized) {
              val diskValues = serializerManager.dataDeserializeStream(
                blockId,
                diskData.toInputStream())(info.classTag)
              maybeCacheDiskValuesInMemory(info, blockId, level, diskValues)
            } else {
              val stream = maybeCacheDiskBytesInMemory(info, blockId, level, diskData)
                .map { _.toInputStream(dispose = false) }
                .getOrElse { diskData.toInputStream() }
              serializerManager.dataDeserializeStream(blockId, stream)(info.classTag)
            }
            val ci = CompletionIterator[Any, Iterator[Any]](iterToReturn, {
              releaseLockAndDispose(blockId, diskData, taskContext)
            })
            Some(new BlockResult(ci, DataReadMethod.Disk, info.size))
          } catch {
            case t: Throwable =>
              if (diskData != null) {
                diskData.dispose()
                diskData = null
              }
              releaseLock(blockId, taskContext)
              if (isIORelatedException(t)) {
                logInfo(extendMessageWithBlockDetails(t.getMessage, blockId))
                // Remove the block so that its unavailability is reported to the driver
                removeBlock(blockId)
              }
              throw t
          }
        } else {
          handleLocalReadFailure(blockId)
        }
    }
  }

  /**
   *  We need to have detailed log message to catch environmental problems easily.
   *  Further details: https://issues.apache.org/jira/browse/SPARK-37710
   */
   private def extendMessageWithBlockDetails(msg: String, blockId: BlockId): String = {
    val message: String = "%s. %s - blockId: %s".format(msg, blockManagerId.toString, blockId)
    val file = diskBlockManager.getFile(blockId)
    if (file.exists()) {
      "%s - blockDiskPath: %s".format(message, file.getAbsolutePath)
    } else {
      message
    }
  }

  /**
   * Get block from the local block manager as serialized bytes.
   */
  def getLocalBytes(blockId: BlockId): Option[BlockData] = {
    logDebug(s"Getting local block $blockId as bytes")
    assert(!blockId.isShuffle, s"Unexpected ShuffleBlockId $blockId")
    blockInfoManager.lockForReading(blockId).map { info => doGetLocalBytes(blockId, info) }
  }

  /**
   * Get block from the local block manager as serialized bytes.
   *
   * Must be called while holding a read lock on the block.
   * Releases the read lock upon exception; keeps the read lock upon successful return.
   */
  private def doGetLocalBytes(blockId: BlockId, info: BlockInfo): BlockData = {
    val level = info.level
    logDebug(s"Level for block $blockId is $level")
    // In order, try to read the serialized bytes from memory, then from disk, then fall back to
    // serializing in-memory objects, and, finally, throw an exception if the block does not exist.
    if (level.deserialized) {
      // Try to avoid expensive serialization by reading a pre-serialized copy from disk:
      if (level.useDisk && diskStore.contains(blockId)) {
        // Note: we purposely do not try to put the block back into memory here. Since this branch
        // handles deserialized blocks, this block may only be cached in memory as objects, not
        // serialized bytes. Because the caller only requested bytes, it doesn't make sense to
        // cache the block's deserialized objects since that caching may not have a payoff.
        diskStore.getBytes(blockId)
      } else if (level.useMemory && memoryStore.contains(blockId)) {
        // The block was not found on disk, so serialize an in-memory copy:
        new ByteBufferBlockData(serializerManager.dataSerializeWithExplicitClassTag(
          blockId, memoryStore.getValues(blockId).get, info.classTag), true)
      } else {
        handleLocalReadFailure(blockId)
      }
    } else {  // storage level is serialized
      if (level.useMemory && memoryStore.contains(blockId)) {
        new ByteBufferBlockData(memoryStore.getBytes(blockId).get, false)
      } else if (level.useDisk && diskStore.contains(blockId)) {
        val diskData = diskStore.getBytes(blockId)
        maybeCacheDiskBytesInMemory(info, blockId, level, diskData)
          .map(new ByteBufferBlockData(_, false))
          .getOrElse(diskData)
      } else {
        handleLocalReadFailure(blockId)
      }
    }
  }

  /**
   * Get block from remote block managers.
   *
   * This does not acquire a lock on this block in this JVM.
   */
  private[spark] def getRemoteValues[T: ClassTag](blockId: BlockId): Option[BlockResult] = {
    val ct = implicitly[ClassTag[T]]
    getRemoteBlock(blockId, (data: ManagedBuffer) => {
      val values =
        serializerManager.dataDeserializeStream(blockId, data.createInputStream())(ct)
      new BlockResult(values, DataReadMethod.Network, data.size)
    })
  }

  /**
   * Get the remote block and transform it to the provided data type.
   *
   * If the block is persisted to the disk and stored at an executor running on the same host then
   * first it is tried to be accessed using the local directories of the other executor directly.
   * If the file is successfully identified then tried to be transformed by the provided
   * transformation function which expected to open the file. If there is any exception during this
   * transformation then block access falls back to fetching it from the remote executor via the
   * network.
   *
   * @param blockId identifies the block to get
   * @param bufferTransformer this transformer expected to open the file if the block is backed by a
   *                          file by this it is guaranteed the whole content can be loaded
   * @tparam T result type
   */
  private[spark] def getRemoteBlock[T](
      blockId: BlockId,
      bufferTransformer: ManagedBuffer => T): Option[T] = {
    logDebug(s"Getting remote block $blockId")
    require(blockId != null, "BlockId is null")

    // Because all the remote blocks are registered in driver, it is not necessary to ask
    // all the storage endpoints to get block status.
    val locationsAndStatusOption = master.getLocationsAndStatus(blockId, blockManagerId.host)
    if (locationsAndStatusOption.isEmpty) {
      logDebug(s"Block $blockId is unknown by block manager master")
      None
    } else {
      val locationsAndStatus = locationsAndStatusOption.get
      val blockSize = locationsAndStatus.status.diskSize.max(locationsAndStatus.status.memSize)

      locationsAndStatus.localDirs.flatMap { localDirs =>
        val blockDataOption =
          readDiskBlockFromSameHostExecutor(blockId, localDirs, locationsAndStatus.status.diskSize)
        val res = blockDataOption.flatMap { blockData =>
          try {
            Some(bufferTransformer(blockData))
          } catch {
            case NonFatal(e) =>
              logDebug("Block from the same host executor cannot be opened: ", e)
              None
          }
        }
        logInfo(s"Read $blockId from the disk of a same host executor is " +
          (if (res.isDefined) "successful." else "failed."))
        res
      }.orElse {
        fetchRemoteManagedBuffer(blockId, blockSize, locationsAndStatus).map(bufferTransformer)
      }
    }
  }

  private def preferExecutors(locations: Seq[BlockManagerId]): Seq[BlockManagerId] = {
    val (executors, shuffleServers) = locations.partition(_.port != externalShuffleServicePort)
    executors ++ shuffleServers
  }

  /**
   * Return a list of locations for the given block, prioritizing the local machine since
   * multiple block managers can share the same host, followed by hosts on the same rack.
   *
   * Within each of the above listed groups (same host, same rack and others) executors are
   * preferred over the external shuffle service.
   */
  private[spark] def sortLocations(locations: Seq[BlockManagerId]): Seq[BlockManagerId] = {
    val locs = Random.shuffle(locations)
    val (preferredLocs, otherLocs) = locs.partition(_.host == blockManagerId.host)
    val orderedParts = blockManagerId.topologyInfo match {
      case None => Seq(preferredLocs, otherLocs)
      case Some(_) =>
        val (sameRackLocs, differentRackLocs) = otherLocs.partition {
          loc => blockManagerId.topologyInfo == loc.topologyInfo
        }
        Seq(preferredLocs, sameRackLocs, differentRackLocs)
    }
    orderedParts.map(preferExecutors).reduce(_ ++ _)
  }

  /**
   * Fetch the block from remote block managers as a ManagedBuffer.
   */
  private def fetchRemoteManagedBuffer(
      blockId: BlockId,
      blockSize: Long,
      locationsAndStatus: BlockManagerMessages.BlockLocationsAndStatus): Option[ManagedBuffer] = {
    // If the block size is above the threshold, we should pass our FileManger to
    // BlockTransferService, which will leverage it to spill the block; if not, then passed-in
    // null value means the block will be persisted in memory.
    val tempFileManager = if (blockSize > maxRemoteBlockToMem) {
      remoteBlockTempFileManager
    } else {
      null
    }
    var runningFailureCount = 0
    var totalFailureCount = 0
    val locations = sortLocations(locationsAndStatus.locations)
    val maxFetchFailures = locations.size
    var locationIterator = locations.iterator
    while (locationIterator.hasNext) {
      val loc = locationIterator.next()
      logDebug(s"Getting remote block $blockId from $loc")
      val data = try {
        val buf = blockTransferService.fetchBlockSync(loc.host, loc.port, loc.executorId,
          blockId.toString, tempFileManager)
        if (blockSize > 0 && buf.size() == 0) {
          throw new IllegalStateException("Empty buffer received for non empty block " +
            s"when fetching remote block $blockId from $loc")
        }
        buf
      } catch {
        case NonFatal(e) =>
          runningFailureCount += 1
          totalFailureCount += 1

          if (totalFailureCount >= maxFetchFailures) {
            // Give up trying anymore locations. Either we've tried all of the original locations,
            // or we've refreshed the list of locations from the master, and have still
            // hit failures after trying locations from the refreshed list.
            logWarning(s"Failed to fetch remote block $blockId " +
              s"from [${locations.mkString(", ")}] after $totalFailureCount fetch failures. " +
              s"Most recent failure cause:", e)
            return None
          }

          logWarning(s"Failed to fetch remote block $blockId " +
            s"from $loc (failed attempt $runningFailureCount)", e)

          // If there is a large number of executors then locations list can contain a
          // large number of stale entries causing a large number of retries that may
          // take a significant amount of time. To get rid of these stale entries
          // we refresh the block locations after a certain number of fetch failures
          if (runningFailureCount >= maxFailuresBeforeLocationRefresh) {
            locationIterator = sortLocations(master.getLocations(blockId)).iterator
            logDebug(s"Refreshed locations from the driver " +
              s"after ${runningFailureCount} fetch failures.")
            runningFailureCount = 0
          }

          // This location failed, so we retry fetch from a different one by returning null here
          null
      }

      if (data != null) {
        // If the ManagedBuffer is a BlockManagerManagedBuffer, the disposal of the
        // byte buffers backing it may need to be handled after reading the bytes.
        // In this case, since we just fetched the bytes remotely, we do not have
        // a BlockManagerManagedBuffer. The assert here is to ensure that this holds
        // true (or the disposal is handled).
        assert(!data.isInstanceOf[BlockManagerManagedBuffer])
        return Some(data)
      }
      logDebug(s"The value of block $blockId is null")
    }
    logDebug(s"Block $blockId not found")
    None
  }

  /**
   * Reads the block from the local directories of another executor which runs on the same host.
   */
  private[spark] def readDiskBlockFromSameHostExecutor(
      blockId: BlockId,
      localDirs: Array[String],
      blockSize: Long): Option[ManagedBuffer] = {
    val file = new File(ExecutorDiskUtils.getFilePath(localDirs, subDirsPerLocalDir, blockId.name))
    if (file.exists()) {
      val managedBuffer = securityManager.getIOEncryptionKey() match {
        case Some(key) =>
          // Encrypted blocks cannot be memory mapped; return a special object that does decryption
          // and provides InputStream / FileRegion implementations for reading the data.
          new EncryptedManagedBuffer(
            new EncryptedBlockData(file, blockSize, conf, key))

        case _ =>
          val transportConf = SparkTransportConf.fromSparkConf(conf, "shuffle")
          new FileSegmentManagedBuffer(transportConf, file, 0, file.length)
      }
      Some(managedBuffer)
    } else {
      None
    }
  }

  /**
   * Get block from remote block managers as serialized bytes.
   */
  def getRemoteBytes(blockId: BlockId): Option[ChunkedByteBuffer] = {
    getRemoteBlock(blockId, (data: ManagedBuffer) => {
      // SPARK-24307 undocumented "escape-hatch" in case there are any issues in converting to
      // ChunkedByteBuffer, to go back to old code-path.  Can be removed post Spark 2.4 if
      // new path is stable.
      if (remoteReadNioBufferConversion) {
        new ChunkedByteBuffer(data.nioByteBuffer())
      } else {
        ChunkedByteBuffer.fromManagedBuffer(data)
      }
    })
  }

  /**
   * Get a block from the block manager (either local or remote).
   *
   * This acquires a read lock on the block if the block was stored locally and does not acquire
   * any locks if the block was fetched from a remote block manager. The read lock will
   * automatically be freed once the result's `data` iterator is fully consumed.
   */
  def get[T: ClassTag](blockId: BlockId): Option[BlockResult] = {
    val local = getLocalValues(blockId)
    if (local.isDefined) {
      logInfo(s"Found block $blockId locally")
      return local
    }
    val remote = getRemoteValues[T](blockId)
    if (remote.isDefined) {
      logInfo(s"Found block $blockId remotely")
      return remote
    }
    None
  }

  /**
   * Downgrades an exclusive write lock to a shared read lock.
   */
  def downgradeLock(blockId: BlockId): Unit = {
    blockInfoManager.downgradeLock(blockId)
  }

  /**
   * Release a lock on the given block with explicit TaskContext.
   * The param `taskContext` should be passed in case we can't get the correct TaskContext,
   * for example, the input iterator of a cached RDD iterates to the end in a child
   * thread.
   */
  def releaseLock(blockId: BlockId, taskContext: Option[TaskContext] = None): Unit = {
    val taskAttemptId = taskContext.map(_.taskAttemptId())
    // SPARK-27666. When a task completes, Spark automatically releases all the blocks locked
    // by this task. We should not release any locks for a task that is already completed.
    if (taskContext.isDefined && taskContext.get.isCompleted) {
      logWarning(s"Task ${taskAttemptId.get} already completed, not releasing lock for $blockId")
    } else {
      blockInfoManager.unlock(blockId, taskAttemptId)
    }
  }

  /**
   * Registers a task with the BlockManager in order to initialize per-task bookkeeping structures.
   */
  def registerTask(taskAttemptId: Long): Unit = {
    blockInfoManager.registerTask(taskAttemptId)
  }

  /**
   * Release all locks for the given task.
   *
   * @return the blocks whose locks were released.
   */
  def releaseAllLocksForTask(taskAttemptId: Long): Seq[BlockId] = {
    blockInfoManager.releaseAllLocksForTask(taskAttemptId)
  }

  /**
   * Retrieve the given block if it exists, otherwise call the provided `makeIterator` method
   * to compute the block, persist it, and return its values.
   *
   * @return either a BlockResult if the block was successfully cached, or an iterator if the block
   *         could not be cached.
   */
  def getOrElseUpdate[T](
      blockId: BlockId,
      level: StorageLevel,
      classTag: ClassTag[T],
      makeIterator: () => Iterator[T]): Either[BlockResult, Iterator[T]] = {
    // Attempt to read the block from local or remote storage. If it's present, then we don't need
    // to go through the local-get-or-put path.
    get[T](blockId)(classTag) match {
      case Some(block) =>
        return Left(block)
      case _ =>
        // Need to compute the block.
    }
    // Initially we hold no locks on this block.
    doPutIterator(blockId, makeIterator, level, classTag, keepReadLock = true) match {
      case None =>
        // doPut() didn't hand work back to us, so the block already existed or was successfully
        // stored. Therefore, we now hold a read lock on the block.
        val blockResult = getLocalValues(blockId).getOrElse {
          // Since we held a read lock between the doPut() and get() calls, the block should not
          // have been evicted, so get() not returning the block indicates some internal error.
          releaseLock(blockId)
          throw SparkCoreErrors.failToGetBlockWithLockError(blockId)
        }
        // We already hold a read lock on the block from the doPut() call and getLocalValues()
        // acquires the lock again, so we need to call releaseLock() here so that the net number
        // of lock acquisitions is 1 (since the caller will only call release() once).
        releaseLock(blockId)
        Left(blockResult)
      case Some(iter) =>
        // The put failed, likely because the data was too large to fit in memory and could not be
        // dropped to disk. Therefore, we need to pass the input iterator back to the caller so
        // that they can decide what to do with the values (e.g. process them without caching).
       Right(iter)
    }
  }

  /**
   * @return true if the block was stored or false if an error occurred.
   */
  def putIterator[T: ClassTag](
      blockId: BlockId,
      values: Iterator[T],
      level: StorageLevel,
      tellMaster: Boolean = true): Boolean = {
    require(values != null, "Values is null")
    doPutIterator(blockId, () => values, level, implicitly[ClassTag[T]], tellMaster) match {
      case None =>
        true
      case Some(iter) =>
        // Caller doesn't care about the iterator values, so we can close the iterator here
        // to free resources earlier
        iter.close()
        false
    }
  }

  /**
   * A short circuited method to get a block writer that can write data directly to disk.
   * The Block will be appended to the File specified by filename. Callers should handle error
   * cases.
   */
  def getDiskWriter(
      blockId: BlockId,
      file: File,
      serializerInstance: SerializerInstance,
      bufferSize: Int,
      writeMetrics: ShuffleWriteMetricsReporter): DiskBlockObjectWriter = {
    val syncWrites = conf.get(config.SHUFFLE_SYNC)
    new DiskBlockObjectWriter(file, serializerManager, serializerInstance, bufferSize,
      syncWrites, writeMetrics, blockId)
  }

  /**
   * Put a new block of serialized bytes to the block manager.
   *
   * '''Important!''' Callers must not mutate or release the data buffer underlying `bytes`. Doing
   * so may corrupt or change the data stored by the `BlockManager`.
   *
   * @return true if the block was stored or false if an error occurred.
   */
  def putBytes[T: ClassTag](
      blockId: BlockId,
      bytes: ChunkedByteBuffer,
      level: StorageLevel,
      tellMaster: Boolean = true): Boolean = {
    require(bytes != null, "Bytes is null")
    val blockStoreUpdater =
      ByteBufferBlockStoreUpdater(blockId, level, implicitly[ClassTag[T]], bytes, tellMaster)
    blockStoreUpdater.save()
  }

  /**
   * Helper method used to abstract common code from [[BlockStoreUpdater.save()]]
   * and [[doPutIterator()]].
   *
   * @param putBody a function which attempts the actual put() and returns None on success
   *                or Some on failure.
   */
  private def doPut[T](
      blockId: BlockId,
      level: StorageLevel,
      classTag: ClassTag[_],
      tellMaster: Boolean,
      keepReadLock: Boolean)(putBody: BlockInfo => Option[T]): Option[T] = {

    require(blockId != null, "BlockId is null")
    require(level != null && level.isValid, "StorageLevel is null or invalid")
    checkShouldStore(blockId)

    val putBlockInfo = {
      val newInfo = new BlockInfo(level, classTag, tellMaster)
      if (blockInfoManager.lockNewBlockForWriting(blockId, newInfo)) {
        newInfo
      } else {
        logWarning(s"Block $blockId already exists on this machine; not re-adding it")
        if (!keepReadLock) {
          // lockNewBlockForWriting returned a read lock on the existing block, so we must free it:
          releaseLock(blockId)
        }
        return None
      }
    }

    val startTimeNs = System.nanoTime()
    var exceptionWasThrown: Boolean = true
    val result: Option[T] = try {
      val res = putBody(putBlockInfo)
      exceptionWasThrown = false
      if (res.isEmpty) {
        // the block was successfully stored
        if (keepReadLock) {
          blockInfoManager.downgradeLock(blockId)
        } else {
          blockInfoManager.unlock(blockId)
        }
      } else {
        removeBlockInternal(blockId, tellMaster = false)
        logWarning(s"Putting block $blockId failed")
      }
      res
    } catch {
      // Since removeBlockInternal may throw exception,
      // we should print exception first to show root cause.
      case NonFatal(e) =>
        logWarning(s"Putting block $blockId failed due to exception $e.")
        throw e
    } finally {
      // This cleanup is performed in a finally block rather than a `catch` to avoid having to
      // catch and properly re-throw InterruptedException.
      if (exceptionWasThrown) {
        // If an exception was thrown then it's possible that the code in `putBody` has already
        // notified the master about the availability of this block, so we need to send an update
        // to remove this block location.
        removeBlockInternal(blockId, tellMaster = tellMaster)
        // The `putBody` code may have also added a new block status to TaskMetrics, so we need
        // to cancel that out by overwriting it with an empty block status. We only do this if
        // the finally block was entered via an exception because doing this unconditionally would
        // cause us to send empty block statuses for every block that failed to be cached due to
        // a memory shortage (which is an expected failure, unlike an uncaught exception).
        addUpdatedBlockStatusToTaskMetrics(blockId, BlockStatus.empty)
      }
    }
    val usedTimeMs = Utils.getUsedTimeNs(startTimeNs)
    if (level.replication > 1) {
      logDebug(s"Putting block ${blockId} with replication took $usedTimeMs")
    } else {
      logDebug(s"Putting block ${blockId} without replication took ${usedTimeMs}")
    }
    result
  }

  /**
   * Put the given block according to the given level in one of the block stores, replicating
   * the values if necessary.
   *
   * If the block already exists, this method will not overwrite it.
   *
   * @param keepReadLock if true, this method will hold the read lock when it returns (even if the
   *                     block already exists). If false, this method will hold no locks when it
   *                     returns.
   * @return None if the block was already present or if the put succeeded, or Some(iterator)
   *         if the put failed.
   */
  private def doPutIterator[T](
      blockId: BlockId,
      iterator: () => Iterator[T],
      level: StorageLevel,
      classTag: ClassTag[T],
      tellMaster: Boolean = true,
      keepReadLock: Boolean = false): Option[PartiallyUnrolledIterator[T]] = {
    doPut(blockId, level, classTag, tellMaster = tellMaster, keepReadLock = keepReadLock) { info =>
      val startTimeNs = System.nanoTime()
      var iteratorFromFailedMemoryStorePut: Option[PartiallyUnrolledIterator[T]] = None
      // Size of the block in bytes
      var size = 0L
      if (level.useMemory) {
        // Put it in memory first, even if it also has useDisk set to true;
        // We will drop it to disk later if the memory store can't hold it.
        if (level.deserialized) {
          memoryStore.putIteratorAsValues(blockId, iterator(), level.memoryMode, classTag) match {
            case Right(s) =>
              size = s
            case Left(iter) =>
              // Not enough space to unroll this block; drop to disk if applicable
              if (level.useDisk) {
                logWarning(s"Persisting block $blockId to disk instead.")
                diskStore.put(blockId) { channel =>
                  val out = Channels.newOutputStream(channel)
                  serializerManager.dataSerializeStream(blockId, out, iter)(classTag)
                }
                size = diskStore.getSize(blockId)
              } else {
                iteratorFromFailedMemoryStorePut = Some(iter)
              }
          }
        } else { // !level.deserialized
          memoryStore.putIteratorAsBytes(blockId, iterator(), classTag, level.memoryMode) match {
            case Right(s) =>
              size = s
            case Left(partiallySerializedValues) =>
              // Not enough space to unroll this block; drop to disk if applicable
              if (level.useDisk) {
                logWarning(s"Persisting block $blockId to disk instead.")
                diskStore.put(blockId) { channel =>
                  val out = Channels.newOutputStream(channel)
                  partiallySerializedValues.finishWritingToStream(out)
                }
                size = diskStore.getSize(blockId)
              } else {
                iteratorFromFailedMemoryStorePut = Some(partiallySerializedValues.valuesIterator)
              }
          }
        }

      } else if (level.useDisk) {
        diskStore.put(blockId) { channel =>
          val out = Channels.newOutputStream(channel)
          serializerManager.dataSerializeStream(blockId, out, iterator())(classTag)
        }
        size = diskStore.getSize(blockId)
      }

      val putBlockStatus = getCurrentBlockStatus(blockId, info)
      val blockWasSuccessfullyStored = putBlockStatus.storageLevel.isValid
      if (blockWasSuccessfullyStored) {
        // Now that the block is in either the memory or disk store, tell the master about it.
        info.size = size
        if (tellMaster && info.tellMaster) {
          reportBlockStatus(blockId, putBlockStatus)
        }
        addUpdatedBlockStatusToTaskMetrics(blockId, putBlockStatus)
        logDebug(s"Put block $blockId locally took ${Utils.getUsedTimeNs(startTimeNs)}")
        if (level.replication > 1) {
          val remoteStartTimeNs = System.nanoTime()
          val bytesToReplicate = doGetLocalBytes(blockId, info)
          // [SPARK-16550] Erase the typed classTag when using default serialization, since
          // NettyBlockRpcServer crashes when deserializing repl-defined classes.
          // TODO(ekl) remove this once the classloader issue on the remote end is fixed.
          val remoteClassTag = if (!serializerManager.canUseKryo(classTag)) {
            scala.reflect.classTag[Any]
          } else {
            classTag
          }
          try {
            replicate(blockId, bytesToReplicate, level, remoteClassTag)
          } finally {
            bytesToReplicate.dispose()
          }
          logDebug(s"Put block $blockId remotely took ${Utils.getUsedTimeNs(remoteStartTimeNs)}")
        }
      }
      assert(blockWasSuccessfullyStored == iteratorFromFailedMemoryStorePut.isEmpty)
      iteratorFromFailedMemoryStorePut
    }
  }

  /**
   * Attempts to cache spilled bytes read from disk into the MemoryStore in order to speed up
   * subsequent reads. This method requires the caller to hold a read lock on the block.
   *
   * @return a copy of the bytes from the memory store if the put succeeded, otherwise None.
   *         If this returns bytes from the memory store then the original disk store bytes will
   *         automatically be disposed and the caller should not continue to use them. Otherwise,
   *         if this returns None then the original disk store bytes will be unaffected.
   */
  private def maybeCacheDiskBytesInMemory(
      blockInfo: BlockInfo,
      blockId: BlockId,
      level: StorageLevel,
      diskData: BlockData): Option[ChunkedByteBuffer] = {
    require(!level.deserialized)
    if (level.useMemory) {
      // Synchronize on blockInfo to guard against a race condition where two readers both try to
      // put values read from disk into the MemoryStore.
      blockInfo.synchronized {
        if (memoryStore.contains(blockId)) {
          diskData.dispose()
          Some(memoryStore.getBytes(blockId).get)
        } else {
          val allocator = level.memoryMode match {
            case MemoryMode.ON_HEAP => ByteBuffer.allocate _
            case MemoryMode.OFF_HEAP => Platform.allocateDirectBuffer _
          }
          val putSucceeded = memoryStore.putBytes(blockId, diskData.size, level.memoryMode, () => {
            // https://issues.apache.org/jira/browse/SPARK-6076
            // If the file size is bigger than the free memory, OOM will happen. So if we
            // cannot put it into MemoryStore, copyForMemory should not be created. That's why
            // this action is put into a `() => ChunkedByteBuffer` and created lazily.
            diskData.toChunkedByteBuffer(allocator)
          })
          if (putSucceeded) {
            diskData.dispose()
            Some(memoryStore.getBytes(blockId).get)
          } else {
            None
          }
        }
      }
    } else {
      None
    }
  }

  /**
   * Attempts to cache spilled values read from disk into the MemoryStore in order to speed up
   * subsequent reads. This method requires the caller to hold a read lock on the block.
   *
   * @return a copy of the iterator. The original iterator passed this method should no longer
   *         be used after this method returns.
   */
  private def maybeCacheDiskValuesInMemory[T](
      blockInfo: BlockInfo,
      blockId: BlockId,
      level: StorageLevel,
      diskIterator: Iterator[T]): Iterator[T] = {
    require(level.deserialized)
    val classTag = blockInfo.classTag.asInstanceOf[ClassTag[T]]
    if (level.useMemory) {
      // Synchronize on blockInfo to guard against a race condition where two readers both try to
      // put values read from disk into the MemoryStore.
      blockInfo.synchronized {
        if (memoryStore.contains(blockId)) {
          // Note: if we had a means to discard the disk iterator, we would do that here.
          memoryStore.getValues(blockId).get
        } else {
          memoryStore.putIteratorAsValues(blockId, diskIterator, level.memoryMode, classTag) match {
            case Left(iter) =>
              // The memory store put() failed, so it returned the iterator back to us:
              iter
            case Right(_) =>
              // The put() succeeded, so we can read the values back:
              memoryStore.getValues(blockId).get
          }
        }
      }.asInstanceOf[Iterator[T]]
    } else {
      diskIterator
    }
  }

  /**
   * Get peer block managers in the system.
   */
  private[storage] def getPeers(forceFetch: Boolean): Seq[BlockManagerId] = {
    peerFetchLock.synchronized {
      val cachedPeersTtl = conf.get(config.STORAGE_CACHED_PEERS_TTL) // milliseconds
      val diff = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - lastPeerFetchTimeNs)
      val timeout = diff > cachedPeersTtl
      if (cachedPeers == null || forceFetch || timeout) {
        cachedPeers = master.getPeers(blockManagerId).sortBy(_.hashCode)
        lastPeerFetchTimeNs = System.nanoTime()
        logDebug("Fetched peers from master: " + cachedPeers.mkString("[", ",", "]"))
      }
      if (cachedPeers.isEmpty &&
          conf.get(config.STORAGE_DECOMMISSION_FALLBACK_STORAGE_PATH).isDefined) {
        Seq(FallbackStorage.FALLBACK_BLOCK_MANAGER_ID)
      } else {
        cachedPeers
      }
    }
  }

  /**
   * Replicates a block to peer block managers based on existingReplicas and maxReplicas
   *
   * @param blockId blockId being replicate
   * @param existingReplicas existing block managers that have a replica
   * @param maxReplicas maximum replicas needed
   * @param maxReplicationFailures number of replication failures to tolerate before
   *                               giving up.
   * @return whether block was successfully replicated or not
   */
  def replicateBlock(
      blockId: BlockId,
      existingReplicas: Set[BlockManagerId],
      maxReplicas: Int,
      maxReplicationFailures: Option[Int] = None): Boolean = {
    logInfo(s"Using $blockManagerId to pro-actively replicate $blockId")
    blockInfoManager.lockForReading(blockId).forall { info =>
      val data = doGetLocalBytes(blockId, info)
      val storageLevel = StorageLevel(
        useDisk = info.level.useDisk,
        useMemory = info.level.useMemory,
        useOffHeap = info.level.useOffHeap,
        deserialized = info.level.deserialized,
        replication = maxReplicas)
      // we know we are called as a result of an executor removal or because the current executor
      // is getting decommissioned. so we refresh peer cache before trying replication, we won't
      // try to replicate to a missing executor/another decommissioning executor
      getPeers(forceFetch = true)
      try {
        replicate(
          blockId, data, storageLevel, info.classTag, existingReplicas, maxReplicationFailures)
      } finally {
        logDebug(s"Releasing lock for $blockId")
        releaseLockAndDispose(blockId, data)
      }
    }
  }

  /**
   * Replicate block to another node. Note that this is a blocking call that returns after
   * the block has been replicated.
   */
  private def replicate(
      blockId: BlockId,
      data: BlockData,
      level: StorageLevel,
      classTag: ClassTag[_],
      existingReplicas: Set[BlockManagerId] = Set.empty,
      maxReplicationFailures: Option[Int] = None): Boolean = {

    val maxReplicationFailureCount = maxReplicationFailures.getOrElse(
      conf.get(config.STORAGE_MAX_REPLICATION_FAILURE))
    val tLevel = StorageLevel(
      useDisk = level.useDisk,
      useMemory = level.useMemory,
      useOffHeap = level.useOffHeap,
      deserialized = level.deserialized,
      replication = 1)

    val numPeersToReplicateTo = level.replication - 1
    val startTime = System.nanoTime

    val peersReplicatedTo = mutable.HashSet.empty ++ existingReplicas
    val peersFailedToReplicateTo = mutable.HashSet.empty[BlockManagerId]
    var numFailures = 0

    val initialPeers = getPeers(false).filterNot(existingReplicas.contains)

    var peersForReplication = blockReplicationPolicy.prioritize(
      blockManagerId,
      initialPeers,
      peersReplicatedTo,
      blockId,
      numPeersToReplicateTo)

    while(numFailures <= maxReplicationFailureCount &&
      !peersForReplication.isEmpty &&
      peersReplicatedTo.size < numPeersToReplicateTo) {
      val peer = peersForReplication.head
      try {
        val onePeerStartTime = System.nanoTime
        logTrace(s"Trying to replicate $blockId of ${data.size} bytes to $peer")
        // This thread keeps a lock on the block, so we do not want the netty thread to unlock
        // block when it finishes sending the message.
        val buffer = new BlockManagerManagedBuffer(blockInfoManager, blockId, data, false,
          unlockOnDeallocate = false)
        blockTransferService.uploadBlockSync(
          peer.host,
          peer.port,
          peer.executorId,
          blockId,
          buffer,
          tLevel,
          classTag)
        logTrace(s"Replicated $blockId of ${data.size} bytes to $peer" +
          s" in ${(System.nanoTime - onePeerStartTime).toDouble / 1e6} ms")
        peersForReplication = peersForReplication.tail
        peersReplicatedTo += peer
      } catch {
        // Rethrow interrupt exception
        case e: InterruptedException =>
          throw e
        // Everything else we may retry
        case NonFatal(e) =>
          logWarning(s"Failed to replicate $blockId to $peer, failure #$numFailures", e)
          peersFailedToReplicateTo += peer
          // we have a failed replication, so we get the list of peers again
          // we don't want peers we have already replicated to and the ones that
          // have failed previously
          val filteredPeers = getPeers(true).filter { p =>
            !peersFailedToReplicateTo.contains(p) && !peersReplicatedTo.contains(p)
          }

          numFailures += 1
          peersForReplication = blockReplicationPolicy.prioritize(
            blockManagerId,
            filteredPeers,
            peersReplicatedTo,
            blockId,
            numPeersToReplicateTo - peersReplicatedTo.size)
      }
    }
    logDebug(s"Replicating $blockId of ${data.size} bytes to " +
      s"${peersReplicatedTo.size} peer(s) took ${(System.nanoTime - startTime) / 1e6} ms")
    if (peersReplicatedTo.size < numPeersToReplicateTo) {
      logWarning(s"Block $blockId replicated to only " +
        s"${peersReplicatedTo.size} peer(s) instead of $numPeersToReplicateTo peers")
      return false
    }

    logDebug(s"block $blockId replicated to ${peersReplicatedTo.mkString(", ")}")
    true
  }

  /**
   * Read a block consisting of a single object.
   */
  def getSingle[T: ClassTag](blockId: BlockId): Option[T] = {
    get[T](blockId).map(_.data.next().asInstanceOf[T])
  }

  /**
   * Write a block consisting of a single object.
   *
   * @return true if the block was stored or false if the block was already stored or an
   *         error occurred.
   */
  def putSingle[T: ClassTag](
      blockId: BlockId,
      value: T,
      level: StorageLevel,
      tellMaster: Boolean = true): Boolean = {
    putIterator(blockId, Iterator(value), level, tellMaster)
  }

  /**
   * Drop a block from memory, possibly putting it on disk if applicable. Called when the memory
   * store reaches its limit and needs to free up space.
   *
   * If `data` is not put on disk, it won't be created.
   *
   * The caller of this method must hold a write lock on the block before calling this method.
   * This method does not release the write lock.
   *
   * @return the block's new effective StorageLevel.
   */
  private[storage] override def dropFromMemory[T: ClassTag](
      blockId: BlockId,
      data: () => Either[Array[T], ChunkedByteBuffer]): StorageLevel = {
    logInfo(s"Dropping block $blockId from memory")
    val info = blockInfoManager.assertBlockIsLockedForWriting(blockId)
    var blockIsUpdated = false
    val level = info.level

    // Drop to disk, if storage level requires
    if (level.useDisk && !diskStore.contains(blockId)) {
      logInfo(s"Writing block $blockId to disk")
      data() match {
        case Left(elements) =>
          diskStore.put(blockId) { channel =>
            val out = Channels.newOutputStream(channel)
            serializerManager.dataSerializeStream(
              blockId,
              out,
              elements.iterator)(info.classTag.asInstanceOf[ClassTag[T]])
          }
        case Right(bytes) =>
          diskStore.putBytes(blockId, bytes)
      }
      blockIsUpdated = true
    }

    // Actually drop from memory store
    val droppedMemorySize =
      if (memoryStore.contains(blockId)) memoryStore.getSize(blockId) else 0L
    val blockIsRemoved = memoryStore.remove(blockId)
    if (blockIsRemoved) {
      blockIsUpdated = true
    } else {
      logWarning(s"Block $blockId could not be dropped from memory as it does not exist")
    }

    val status = getCurrentBlockStatus(blockId, info)
    if (info.tellMaster) {
      reportBlockStatus(blockId, status, droppedMemorySize)
    }
    if (blockIsUpdated) {
      addUpdatedBlockStatusToTaskMetrics(blockId, status)
    }
    status.storageLevel
  }

  /**
   * Remove all blocks belonging to the given RDD.
   *
   * @return The number of blocks removed.
   */
  def removeRdd(rddId: Int): Int = {
    // TODO: Avoid a linear scan by creating another mapping of RDD.id to blocks.
    logInfo(s"Removing RDD $rddId")
    val blocksToRemove = blockInfoManager.entries.flatMap(_._1.asRDDId).filter(_.rddId == rddId)
    blocksToRemove.foreach { blockId => removeBlock(blockId, tellMaster = false) }
    blocksToRemove.size
  }

  def decommissionBlockManager(): Unit = storageEndpoint.ask(DecommissionBlockManager)

  private[spark] def decommissionSelf(): Unit = synchronized {
    decommissioner match {
      case None =>
        logInfo("Starting block manager decommissioning process...")
        decommissioner = Some(new BlockManagerDecommissioner(conf, this))
        decommissioner.foreach(_.start())
      case Some(_) =>
        logDebug("Block manager already in decommissioning state")
    }
  }

  /**
   *  Returns the last migration time and a boolean denoting if all the blocks have been migrated.
   *  If there are any tasks running since that time the boolean may be incorrect.
   */
  private[spark] def lastMigrationInfo(): (Long, Boolean) = {
    decommissioner.map(_.lastMigrationInfo()).getOrElse((0, false))
  }

  private[storage] def getMigratableRDDBlocks(): Seq[ReplicateBlock] =
    master.getReplicateInfoForRDDBlocks(blockManagerId)

  /**
   * Remove all blocks belonging to the given broadcast.
   */
  def removeBroadcast(broadcastId: Long, tellMaster: Boolean): Int = {
    logDebug(s"Removing broadcast $broadcastId")
    val blocksToRemove = blockInfoManager.entries.map(_._1).collect {
      case bid @ BroadcastBlockId(`broadcastId`, _) => bid
    }
    blocksToRemove.foreach { blockId => removeBlock(blockId, tellMaster) }
    blocksToRemove.size
  }

  /**
   * Remove a block from both memory and disk.
   */
  def removeBlock(blockId: BlockId, tellMaster: Boolean = true): Unit = {
    logDebug(s"Removing block $blockId")
    blockInfoManager.lockForWriting(blockId) match {
      case None =>
        // The block has already been removed; do nothing.
        logWarning(s"Asked to remove block $blockId, which does not exist")
      case Some(info) =>
        removeBlockInternal(blockId, tellMaster = tellMaster && info.tellMaster)
        addUpdatedBlockStatusToTaskMetrics(blockId, BlockStatus.empty)
    }
  }

  /**
   * Internal version of [[removeBlock()]] which assumes that the caller already holds a write
   * lock on the block.
   */
  private def removeBlockInternal(blockId: BlockId, tellMaster: Boolean): Unit = {
    val blockStatus = if (tellMaster) {
      val blockInfo = blockInfoManager.assertBlockIsLockedForWriting(blockId)
      Some(getCurrentBlockStatus(blockId, blockInfo))
    } else None

    // Removals are idempotent in disk store and memory store. At worst, we get a warning.
    val removedFromMemory = memoryStore.remove(blockId)
    val removedFromDisk = diskStore.remove(blockId)
    if (!removedFromMemory && !removedFromDisk) {
      logWarning(s"Block $blockId could not be removed as it was not found on disk or in memory")
    }

    blockInfoManager.removeBlock(blockId)
    if (tellMaster) {
      // Only update storage level from the captured block status before deleting, so that
      // memory size and disk size are being kept for calculating delta.
      reportBlockStatus(blockId, blockStatus.get.copy(storageLevel = StorageLevel.NONE))
    }
  }

  private def addUpdatedBlockStatusToTaskMetrics(blockId: BlockId, status: BlockStatus): Unit = {
    if (conf.get(config.TASK_METRICS_TRACK_UPDATED_BLOCK_STATUSES)) {
      Option(TaskContext.get()).foreach { c =>
        c.taskMetrics().incUpdatedBlockStatuses(blockId -> status)
      }
    }
  }

  def releaseLockAndDispose(
      blockId: BlockId,
      data: BlockData,
      taskContext: Option[TaskContext] = None): Unit = {
    releaseLock(blockId, taskContext)
    data.dispose()
  }

  def stop(): Unit = {
    decommissioner.foreach(_.stop())
    blockTransferService.close()
    if (blockStoreClient ne blockTransferService) {
      // Closing should be idempotent, but maybe not for the NioBlockTransferService.
      blockStoreClient.close()
    }
    remoteBlockTempFileManager.stop()
    diskBlockManager.stop()
    rpcEnv.stop(storageEndpoint)
    blockInfoManager.clear()
    memoryStore.clear()
    futureExecutionContext.shutdownNow()
    logInfo("BlockManager stopped")
  }
}


private[spark] object BlockManager {
  private val ID_GENERATOR = new IdGenerator

  def blockIdsToLocations(
      blockIds: Array[BlockId],
      env: SparkEnv,
      blockManagerMaster: BlockManagerMaster = null): Map[BlockId, Seq[String]] = {

    // blockManagerMaster != null is used in tests
    assert(env != null || blockManagerMaster != null)
    val blockLocations: Seq[Seq[BlockManagerId]] = if (blockManagerMaster == null) {
      env.blockManager.getLocationBlockIds(blockIds)
    } else {
      blockManagerMaster.getLocations(blockIds)
    }

    val blockManagers = new HashMap[BlockId, Seq[String]]
    for (i <- blockIds.indices) {
      blockManagers(blockIds(i)) = blockLocations(i).map { loc =>
        ExecutorCacheTaskLocation(loc.host, loc.executorId).toString
      }
    }
    blockManagers.toMap
  }

  private class ShuffleMetricsSource(
      override val sourceName: String,
      metricSet: MetricSet) extends Source {

    override val metricRegistry = new MetricRegistry
    metricRegistry.registerAll(metricSet)
  }

  class RemoteBlockDownloadFileManager(
       blockManager: BlockManager,
       encryptionKey: Option[Array[Byte]])
      extends DownloadFileManager with Logging {

    private class ReferenceWithCleanup(
        file: DownloadFile,
        referenceQueue: JReferenceQueue[DownloadFile]
        ) extends WeakReference[DownloadFile](file, referenceQueue) {

      // we cannot use `file.delete()` here otherwise it won't be garbage-collected
      val filePath = file.path()

      def cleanUp(): Unit = {
        logDebug(s"Clean up file $filePath")

        if (!new File(filePath).delete()) {
          logDebug(s"Fail to delete file $filePath")
        }
      }
    }

    private val referenceQueue = new JReferenceQueue[DownloadFile]
    private val referenceBuffer = Collections.newSetFromMap[ReferenceWithCleanup](
      new ConcurrentHashMap)

    private val POLL_TIMEOUT = 1000
    @volatile private var stopped = false

    private val cleaningThread = new Thread() { override def run(): Unit = { keepCleaning() } }
    cleaningThread.setDaemon(true)
    cleaningThread.setName("RemoteBlock-temp-file-clean-thread")
    cleaningThread.start()

    override def createTempFile(transportConf: TransportConf): DownloadFile = {
      val file = blockManager.diskBlockManager.createTempLocalBlock()._2
      encryptionKey match {
        case Some(key) =>
          // encryption is enabled, so when we read the decrypted data off the network, we need to
          // encrypt it when writing to disk.  Note that the data may have been encrypted when it
          // was cached on disk on the remote side, but it was already decrypted by now (see
          // EncryptedBlockData).
          new EncryptedDownloadFile(file, key)
        case None =>
          new SimpleDownloadFile(file, transportConf)
      }
    }

    override def registerTempFileToClean(file: DownloadFile): Boolean = {
      referenceBuffer.add(new ReferenceWithCleanup(file, referenceQueue))
    }

    def stop(): Unit = {
      stopped = true
      cleaningThread.interrupt()
      cleaningThread.join()
    }

    private def keepCleaning(): Unit = {
      while (!stopped) {
        try {
          Option(referenceQueue.remove(POLL_TIMEOUT))
            .map(_.asInstanceOf[ReferenceWithCleanup])
            .foreach { ref =>
              referenceBuffer.remove(ref)
              ref.cleanUp()
            }
        } catch {
          case _: InterruptedException =>
            // no-op
          case NonFatal(e) =>
            logError("Error in cleaning thread", e)
        }
      }
    }
  }

  /**
   * A DownloadFile that encrypts data when it is written, and decrypts when it's read.
   */
  private class EncryptedDownloadFile(
      file: File,
      key: Array[Byte]) extends DownloadFile {

    private val env = SparkEnv.get

    override def delete(): Boolean = file.delete()

    override def openForWriting(): DownloadFileWritableChannel = {
      new EncryptedDownloadWritableChannel()
    }

    override def path(): String = file.getAbsolutePath

    private class EncryptedDownloadWritableChannel extends DownloadFileWritableChannel {
      private val countingOutput: CountingWritableChannel = new CountingWritableChannel(
        Channels.newChannel(env.serializerManager.wrapForEncryption(new FileOutputStream(file))))

      override def closeAndRead(): ManagedBuffer = {
        countingOutput.close()
        val size = countingOutput.getCount
        new EncryptedManagedBuffer(new EncryptedBlockData(file, size, env.conf, key))
      }

      override def write(src: ByteBuffer): Int = countingOutput.write(src)

      override def isOpen: Boolean = countingOutput.isOpen()

      override def close(): Unit = countingOutput.close()
    }
  }
}

相关信息

spark 源码目录

相关文章

spark BlockException 源码

spark BlockId 源码

spark BlockInfoManager 源码

spark BlockManagerDecommissioner 源码

spark BlockManagerId 源码

spark BlockManagerManagedBuffer 源码

spark BlockManagerMaster 源码

spark BlockManagerMasterEndpoint 源码

spark BlockManagerMasterHeartbeatEndpoint 源码

spark BlockManagerMessages 源码

0  赞