[SPARK-20732][CORE] Decommission cache blocks to other executors when an executor is decommissioned

core/src/main/scala/org/apache/spark/internal/config/package.scala

@@ -413,6 +413,34 @@ package object config {
       .intConf
       .createWithDefault(1)
 
+  private[spark] val STORAGE_DECOMMISSION_ENABLED =
+    ConfigBuilder("spark.storage.decommission.enabled")
+      .doc("Whether to decommission the block manager when decommissioning executor")
+      .version("3.1.0")
+      .booleanConf
+      .createWithDefault(false)
+
+  private[spark] val STORAGE_DECOMMISSION_MAX_REPLICATION_FAILURE_PER_BLOCK =
+    ConfigBuilder("spark.storage.decommission.maxReplicationFailuresPerBlock")
+      .internal()
+      .doc("Maximum number of failures which can be handled for the replication of " +
+        "one RDD block when block manager is decommissioning and trying to move its " +
+        "existing blocks.")
+      .version("3.1.0")
+      .intConf
+      .createWithDefault(3)
+
+  private[spark] val STORAGE_DECOMMISSION_REPLICATION_REATTEMPT_INTERVAL =
+    ConfigBuilder("spark.storage.decommission.replicationReattemptInterval")
+      .internal()
+      .doc("The interval of time between consecutive cache block replication reattempts " +
+        "happening on each decommissioning executor (due to storage decommissioning).")
+      .version("3.1.0")
+      .timeConf(TimeUnit.MILLISECONDS)
+      .checkValue(_ > 0, "Time interval between two consecutive attempts of " +
+        "cache block replication should be positive.")
+      .createWithDefaultString("30s")
+
   private[spark] val STORAGE_REPLICATION_TOPOLOGY_FILE =
     ConfigBuilder("spark.storage.replication.topologyFile")
       .version("2.1.0")

core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedSchedulerBackend.scala

@@ -438,6 +438,19 @@ class CoarseGrainedSchedulerBackend(scheduler: TaskSchedulerImpl, val rpcEnv: Rp
             logError(s"Unexpected error during decommissioning ${e.toString}", e)
         }
         logInfo(s"Finished decommissioning executor $executorId.")
+
+        if (conf.get(STORAGE_DECOMMISSION_ENABLED)) {
+          try {
+            logInfo("Starting decommissioning block manager corresponding to " +
+              s"executor $executorId.")
+            scheduler.sc.env.blockManager.master.decommissionBlockManagers(Seq(executorId))
+          } catch {
+            case e: Exception =>
+              logError("Unexpected error during block manager " +
+                s"decommissioning for executor $executorId: ${e.toString}", e)
+          }
+          logInfo(s"Acknowledged decommissioning block manager corresponding to $executorId.")
+        }
       } else {
         logInfo(s"Skipping decommissioning of executor $executorId.")
       }
@@ -574,7 +587,7 @@ class CoarseGrainedSchedulerBackend(scheduler: TaskSchedulerImpl, val rpcEnv: Rp
    */
   private[spark] def decommissionExecutor(executorId: String): Unit = {
     if (driverEndpoint != null) {
-      logInfo("Propegating executor decommission to driver.")
+      logInfo("Propagating executor decommission to driver.")
       driverEndpoint.send(DecommissionExecutor(executorId))
     }
   }
@@ -658,7 +671,7 @@ class CoarseGrainedSchedulerBackend(scheduler: TaskSchedulerImpl, val rpcEnv: Rp
   /**
    * Update the cluster manager on our scheduling needs. Three bits of information are included
    * to help it make decisions.
-   * @param resourceProfileToNumExecutors The total number of executors we'd like to have per
+   * @param resourceProfileIdToNumExecutors The total number of executors we'd like to have per
    *                                      ResourceProfile. The cluster manager shouldn't kill any
    *                                      running executor to reach this number, but, if all
    *                                      existing executors were to die, this is the number

core/src/main/scala/org/apache/spark/storage/BlockManager.scala

@@ -54,6 +54,7 @@ import org.apache.spark.rpc.RpcEnv
 import org.apache.spark.scheduler.ExecutorCacheTaskLocation
 import org.apache.spark.serializer.{SerializerInstance, SerializerManager}
 import org.apache.spark.shuffle.{ShuffleManager, ShuffleWriteMetricsReporter}
+import org.apache.spark.storage.BlockManagerMessages.ReplicateBlock
 import org.apache.spark.storage.memory._
 import org.apache.spark.unsafe.Platform
 import org.apache.spark.util._
@@ -241,6 +242,9 @@ private[spark] class BlockManager(
 
   private var blockReplicationPolicy: BlockReplicationPolicy = _
 
+  private var blockManagerDecommissioning: Boolean = false
+  private var decommissionManager: Option[BlockManagerDecommissionManager] = 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
@@ -1551,30 +1555,36 @@ private[spark] class BlockManager(
   }
 
   /**
-   * Called for pro-active replenishment of blocks lost due to executor failures
+   * 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): Unit = {
+      maxReplicas: Int,
+      maxReplicationFailures: Option[Int] = None): Boolean = {
     logInfo(s"Using $blockManagerId to pro-actively replicate $blockId")
-    blockInfoManager.lockForReading(blockId).foreach { info =>
+    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, so we refresh peer cache
-      // this way, we won't try to replicate to a missing executor with a stale reference
+      // 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)
+        replicate(
+          blockId, data, storageLevel, info.classTag, existingReplicas, maxReplicationFailures)
       } finally {
         logDebug(s"Releasing lock for $blockId")
         releaseLockAndDispose(blockId, data)
@@ -1591,9 +1601,11 @@ private[spark] class BlockManager(
       data: BlockData,
       level: StorageLevel,
       classTag: ClassTag[_],
-      existingReplicas: Set[BlockManagerId] = Set.empty): Unit = {
+      existingReplicas: Set[BlockManagerId] = Set.empty,
+      maxReplicationFailures: Option[Int] = None): Boolean = {
 
-    val maxReplicationFailures = conf.get(config.STORAGE_MAX_REPLICATION_FAILURE)
+    val maxReplicationFailureCount = maxReplicationFailures.getOrElse(
+      conf.get(config.STORAGE_MAX_REPLICATION_FAILURE))
     val tLevel = StorageLevel(
       useDisk = level.useDisk,
       useMemory = level.useMemory,
@@ -1617,7 +1629,7 @@ private[spark] class BlockManager(
       blockId,
       numPeersToReplicateTo)
 
-    while(numFailures <= maxReplicationFailures &&
+    while(numFailures <= maxReplicationFailureCount &&
       !peersForReplication.isEmpty &&
       peersReplicatedTo.size < numPeersToReplicateTo) {
       val peer = peersForReplication.head
@@ -1665,9 +1677,11 @@ private[spark] class BlockManager(
     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(", ")}")
+    return true
   }
 
   /**
@@ -1761,6 +1775,58 @@ private[spark] class BlockManager(
     blocksToRemove.size
   }
 
+  def decommissionBlockManager(): Unit = {
+    if (!blockManagerDecommissioning) {
+      logInfo("Starting block manager decommissioning process")
+      blockManagerDecommissioning = true
+      decommissionManager = Some(new BlockManagerDecommissionManager(conf))
+      decommissionManager.foreach(_.start())
+    } else {
+      logDebug("Block manager already in decommissioning state")
+    }
+  }
+
+  /**
+   * Tries to offload all cached RDD blocks from this BlockManager to peer BlockManagers
+   * Visible for testing
+   */
+  def decommissionRddCacheBlocks(): Unit = {
+    val replicateBlocksInfo = master.getReplicateInfoForRDDBlocks(blockManagerId)
+
+    if (replicateBlocksInfo.nonEmpty) {
+      logInfo(s"Need to replicate ${replicateBlocksInfo.size} blocks " +
+        "for block manager decommissioning")
+    }
+
+    // Maximum number of storage replication failure which replicateBlock can handle
+    val maxReplicationFailures = conf.get(
+      config.STORAGE_DECOMMISSION_MAX_REPLICATION_FAILURE_PER_BLOCK)
+
+    // TODO: We can sort these blocks based on some policy (LRU/blockSize etc)
+    //   so that we end up prioritize them over each other
+    val blocksFailedReplication = ThreadUtils.parmap(
+      replicateBlocksInfo, "decommissionRddCacheBlocks", 4) {
+      case ReplicateBlock(blockId, existingReplicas, maxReplicas) =>
+        val replicatedSuccessfully = replicateBlock(
+          blockId,
+          existingReplicas.toSet,
+          maxReplicas,
+          maxReplicationFailures = Some(maxReplicationFailures))
+        if (replicatedSuccessfully) {
+          logInfo(s"Block $blockId offloaded successfully, Removing block now")
+          removeBlock(blockId)
+          logInfo(s"Block $blockId removed")
+        } else {
+          logWarning(s"Failed to offload block $blockId")
+        }
+        (blockId, replicatedSuccessfully)
+    }.filterNot(_._2).map(_._1)
+    if (blocksFailedReplication.nonEmpty) {
+      logWarning("Blocks failed replication in cache decommissioning " +
+        s"process: ${blocksFailedReplication.mkString(",")}")
+    }
+  }
+
   /**
    * Remove all blocks belonging to the given broadcast.
    */
@@ -1829,7 +1895,52 @@ private[spark] class BlockManager(
     data.dispose()
   }
 
+  /**
+   * Class to handle block manager decommissioning retries
+   * It creates a Thread to retry offloading all RDD cache blocks
+   */
+  private class BlockManagerDecommissionManager(conf: SparkConf) {
+    @volatile private var stopped = false
+    private val blockReplicationThread = new Thread {
+      override def run(): Unit = {
+        while (blockManagerDecommissioning && !stopped) {
+          try {
+            logDebug("Attempting to replicate all cached RDD blocks")
+            decommissionRddCacheBlocks()
+            logInfo("Attempt to replicate all cached blocks done")
+            val sleepInterval = conf.get(
+              config.STORAGE_DECOMMISSION_REPLICATION_REATTEMPT_INTERVAL)
+            Thread.sleep(sleepInterval)
+          } catch {
+            case _: InterruptedException =>
+              // no-op
+            case NonFatal(e) =>
+              logError("Error occurred while trying to " +
+                "replicate cached RDD blocks for block manager decommissioning", e)
+          }
+        }
+      }
+    }
+    blockReplicationThread.setDaemon(true)
+    blockReplicationThread.setName("block-replication-thread")
+
+    def start(): Unit = {
+      logInfo("Starting block replication thread")
+      blockReplicationThread.start()
+    }
+
+    def stop(): Unit = {
+      if (!stopped) {
+        stopped = true
+        logInfo("Stopping block replication thread")
+        blockReplicationThread.interrupt()
+        blockReplicationThread.join()
+      }
+    }
+  }
+
   def stop(): Unit = {
+    decommissionManager.foreach(_.stop())
     blockTransferService.close()
     if (blockStoreClient ne blockTransferService) {
       // Closing should be idempotent, but maybe not for the NioBlockTransferService.

core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala

@@ -43,6 +43,16 @@ class BlockManagerMaster(
     logInfo("Removed " + execId + " successfully in removeExecutor")
   }
 
+  /** Decommission block managers corresponding to given set of executors */
+  def decommissionBlockManagers(executorIds: Seq[String]): Unit = {
+    driverEndpoint.ask[Unit](DecommissionBlockManagers(executorIds))
+  }
+
+  /** Get Replication Info for all the RDD blocks stored in given blockManagerId */
+  def getReplicateInfoForRDDBlocks(blockManagerId: BlockManagerId): Seq[ReplicateBlock] = {
+    driverEndpoint.askSync[Seq[ReplicateBlock]](GetReplicateInfoForRDDBlocks(blockManagerId))
+  }
+
   /** Request removal of a dead executor from the driver endpoint.
    *  This is only called on the driver side. Non-blocking
    */

core/src/main/scala/org/apache/spark/storage/BlockManagerMasterEndpoint.scala

@@ -65,6 +65,9 @@ class BlockManagerMasterEndpoint(
   // Mapping from executor ID to block manager ID.
   private val blockManagerIdByExecutor = new mutable.HashMap[String, BlockManagerId]
 
+  // Set of block managers which are decommissioning
+  private val decommissioningBlockManagerSet = new mutable.HashSet[BlockManagerId]
+
   // Mapping from block id to the set of block managers that have the block.
   private val blockLocations = new JHashMap[BlockId, mutable.HashSet[BlockManagerId]]
 
@@ -153,6 +156,13 @@ class BlockManagerMasterEndpoint(
       removeExecutor(execId)
       context.reply(true)
 
+    case DecommissionBlockManagers(executorIds) =>
+      decommissionBlockManagers(executorIds.flatMap(blockManagerIdByExecutor.get))
+      context.reply(true)
+
+    case GetReplicateInfoForRDDBlocks(blockManagerId) =>
+      context.reply(getReplicateInfoForRDDBlocks(blockManagerId))
+
     case StopBlockManagerMaster =>
       context.reply(true)
       stop()
@@ -257,6 +267,7 @@ class BlockManagerMasterEndpoint(
 
     // Remove the block manager from blockManagerIdByExecutor.
     blockManagerIdByExecutor -= blockManagerId.executorId
+    decommissioningBlockManagerSet.remove(blockManagerId)
 
     // Remove it from blockManagerInfo and remove all the blocks.
     blockManagerInfo.remove(blockManagerId)
@@ -299,6 +310,39 @@ class BlockManagerMasterEndpoint(
     blockManagerIdByExecutor.get(execId).foreach(removeBlockManager)
   }
 
+  /**
+   * Decommission the given Seq of blockmanagers
+   *    - Adds these block managers to decommissioningBlockManagerSet Set
+   *    - Sends the DecommissionBlockManager message to each of the [[BlockManagerSlaveEndpoint]]
+   */
+  def decommissionBlockManagers(blockManagerIds: Seq[BlockManagerId]): Future[Seq[Unit]] = {
+    val newBlockManagersToDecommission = blockManagerIds.toSet.diff(decommissioningBlockManagerSet)
+    val futures = newBlockManagersToDecommission.map { blockManagerId =>
+      decommissioningBlockManagerSet.add(blockManagerId)
+      val info = blockManagerInfo(blockManagerId)
+      info.slaveEndpoint.ask[Unit](DecommissionBlockManager)
+    }
+    Future.sequence{ futures.toSeq }
+  }
+
+  /**
+   * Returns a Seq of ReplicateBlock for each RDD block stored by given blockManagerId
+   * @param blockManagerId - block manager id for which ReplicateBlock info is needed
+   * @return Seq of ReplicateBlock
+   */
+  private def getReplicateInfoForRDDBlocks(blockManagerId: BlockManagerId): Seq[ReplicateBlock] = {
+    val info = blockManagerInfo(blockManagerId)
+
+    val rddBlocks = info.blocks.keySet().asScala.filter(_.isRDD)
+    rddBlocks.map { blockId =>
+      val currentBlockLocations = blockLocations.get(blockId)
+      val maxReplicas = currentBlockLocations.size + 1
+      val remainingLocations = currentBlockLocations.toSeq.filter(bm => bm != blockManagerId)
+      val replicateMsg = ReplicateBlock(blockId, remainingLocations, maxReplicas)
+      replicateMsg
+    }.toSeq
+  }
+
   // Remove a block from the slaves that have it. This can only be used to remove
   // blocks that the master knows about.
   private def removeBlockFromWorkers(blockId: BlockId): Unit = {
@@ -536,7 +580,11 @@ class BlockManagerMasterEndpoint(
   private def getPeers(blockManagerId: BlockManagerId): Seq[BlockManagerId] = {
     val blockManagerIds = blockManagerInfo.keySet
     if (blockManagerIds.contains(blockManagerId)) {
-      blockManagerIds.filterNot { _.isDriver }.filterNot { _ == blockManagerId }.toSeq
+      blockManagerIds
+        .filterNot { _.isDriver }
+        .filterNot { _ == blockManagerId }
+        .diff(decommissioningBlockManagerSet)
+        .toSeq
     } else {
       Seq.empty
     }