[GitHub] [spark] agrawaldevesh commented on a change in pull request #28708: [SPARK-20629][CORE][K8S] Copy shuffle data when nodes are being shutdown

[GitBox <gi...@apache.org>]

agrawaldevesh commented on a change in pull request #28708:
URL: https://github.com/apache/spark/pull/28708#discussion_r455424422



##########
File path: core/src/main/scala/org/apache/spark/network/netty/NettyBlockTransferService.scala
##########
@@ -168,7 +168,10 @@ private[spark] class NettyBlockTransferService(
     // Everything else is encoded using our binary protocol.
     val metadata = JavaUtils.bufferToArray(serializer.newInstance().serialize((level, classTag)))
 
-    val asStream = blockData.size() > conf.get(config.MAX_REMOTE_BLOCK_SIZE_FETCH_TO_MEM)
+    // We always transfer shuffle blocks as a stream for simplicity with the receiving code since
+    // they are always written to disk. Otherwise we check the block size.
+    val asStream = (blockData.size() > conf.get(config.MAX_REMOTE_BLOCK_SIZE_FETCH_TO_MEM) ||

Review comment:
       nit: A parentheses isn't quite needed, but even if it is, then would it be easier to read this as:
   
   val asStream = (blockData.size() > conf.get(config.MAX_REMOTE_BLOCK_SIZE_FETCH_TO_MEM) || blockId.isShuffle

##########
File path: core/src/main/scala/org/apache/spark/storage/BlockId.scala
##########
@@ -38,7 +38,10 @@ sealed abstract class BlockId {
   // convenience methods
   def asRDDId: Option[RDDBlockId] = if (isRDD) Some(asInstanceOf[RDDBlockId]) else None
   def isRDD: Boolean = isInstanceOf[RDDBlockId]
-  def isShuffle: Boolean = isInstanceOf[ShuffleBlockId] || isInstanceOf[ShuffleBlockBatchId]
+  def isShuffle: Boolean = {
+    (isInstanceOf[ShuffleBlockId] || isInstanceOf[ShuffleBlockBatchId] ||

Review comment:
       nit: Are the parentheses needed ?

##########
File path: core/src/main/scala/org/apache/spark/storage/BlockManagerDecommissioner.scala
##########
@@ -0,0 +1,330 @@
+/*
+ * 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.util.concurrent.ExecutorService
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.util.control.NonFatal
+
+import org.apache.spark._
+import org.apache.spark.internal.Logging
+import org.apache.spark.internal.config
+import org.apache.spark.shuffle.{MigratableResolver, ShuffleBlockInfo}
+import org.apache.spark.storage.BlockManagerMessages.ReplicateBlock
+import org.apache.spark.util.ThreadUtils
+
+/**
+ * Class to handle block manager decommissioning retries.
+ * It creates a Thread to retry offloading all RDD cache and Shuffle blocks
+ */
+private[storage] class BlockManagerDecommissioner(
+  conf: SparkConf,
+  bm: BlockManager) extends Logging {
+
+  private val maxReplicationFailuresForDecommission =
+    conf.get(config.STORAGE_DECOMMISSION_MAX_REPLICATION_FAILURE_PER_BLOCK)
+
+  /**
+   * This runnable consumes any shuffle blocks in the queue for migration. This part of a
+   * producer/consumer where the main migration loop updates the queue of blocks to be migrated
+   * periodically. On migration failure, the current thread will reinsert the block for another
+   * thread to consume. Each thread migrates blocks to a different particular executor to avoid
+   * distribute the blocks as quickly as possible without overwhelming any particular executor.
+   *
+   * There is no preference for which peer a given block is migrated to.
+   * This is notable different than the RDD cache block migration (further down in this file)
+   * which uses the existing priority mechanism for determining where to replicate blocks to.
+   * Generally speaking cache blocks are less impactful as they normally represent narrow
+   * transformations and we normally have less cache present than shuffle data.
+   *
+   * The producer/consumer model is chosen for shuffle block migration to maximize
+   * the chance of migrating all shuffle blocks before the executor is forced to exit.
+   */
+  private class ShuffleMigrationRunnable(peer: BlockManagerId) extends Runnable {
+    @volatile var running = true
+    override def run(): Unit = {
+      var migrating: Option[(ShuffleBlockInfo, Int)] = None
+      logInfo(s"Starting migration thread for ${peer}")
+      // Once a block fails to transfer to an executor stop trying to transfer more blocks
+      try {
+        while (running && !Thread.interrupted()) {
+          migrating = Option(shufflesToMigrate.poll())
+          migrating match {
+            case None =>
+              logDebug("Nothing to migrate")
+              // Nothing to do right now, but maybe a transfer will fail or a new block
+              // will finish being committed.
+              val SLEEP_TIME_SECS = 1
+              Thread.sleep(SLEEP_TIME_SECS * 1000L)
+            case Some((shuffleBlockInfo, retryCount)) =>
+              if (retryCount < maxReplicationFailuresForDecommission) {
+                logInfo(s"Trying to migrate shuffle ${shuffleBlockInfo} to ${peer}")
+                val blocks =
+                  bm.migratableResolver.getMigrationBlocks(shuffleBlockInfo)
+                logDebug(s"Got migration sub-blocks ${blocks}")
+                blocks.foreach { case (blockId, buffer) =>
+                  logDebug(s"Migrating sub-block ${blockId}")
+                  bm.blockTransferService.uploadBlockSync(
+                    peer.host,
+                    peer.port,
+                    peer.executorId,
+                    blockId,
+                    buffer,
+                    StorageLevel.DISK_ONLY,
+                    null)// class tag, we don't need for shuffle
+                  logDebug(s"Migrated sub block ${blockId}")
+                }
+                logInfo(s"Migrated ${shuffleBlockInfo} to ${peer}")
+              } else {
+                logError(s"Skipping block ${shuffleBlockInfo} because it has failed ${retryCount}")
+              }
+          }
+        }
+        // This catch is intentionally outside of the while running block.
+        // if we encounter errors migrating to an executor we want to stop.
+      } catch {
+        case e: Exception =>
+          migrating match {
+            case Some((shuffleMap, retryCount)) =>
+              logError(s"Error during migration, adding ${shuffleMap} back to migration queue", e)
+              shufflesToMigrate.add((shuffleMap, retryCount + 1))
+            case None =>
+              logError(s"Error while waiting for block to migrate", e)
+          }
+      }
+    }
+  }
+
+  // Shuffles which are either in queue for migrations or migrated
+  private val migratingShuffles = mutable.HashSet[ShuffleBlockInfo]()
+
+  // Shuffles which are queued for migration & number of retries so far.
+  private[storage] val shufflesToMigrate =
+    new java.util.concurrent.ConcurrentLinkedQueue[(ShuffleBlockInfo, Int)]()
+
+  // Set if we encounter an error attempting to migrate and stop.
+  @volatile private var stopped = false
+
+  private val migrationPeers =
+    mutable.HashMap[BlockManagerId, ShuffleMigrationRunnable]()
+
+  private lazy val rddBlockMigrationExecutor =
+    ThreadUtils.newDaemonSingleThreadExecutor("block-manager-decommission-rdd")
+
+  private val rddBlockMigrationRunnable = new Runnable {
+    val sleepInterval = conf.get(config.STORAGE_DECOMMISSION_REPLICATION_REATTEMPT_INTERVAL)
+
+    override def run(): Unit = {
+      assert(conf.get(config.STORAGE_DECOMMISSION_RDD_BLOCKS_ENABLED))
+      while (!stopped && !Thread.interrupted()) {
+        logInfo("Iterating on migrating from the block manager.")
+        try {
+          logDebug("Attempting to replicate all cached RDD blocks")
+          decommissionRddCacheBlocks()
+          logInfo("Attempt to replicate all cached blocks done")
+          logInfo(s"Waiting for ${sleepInterval} before refreshing migrations.")
+          Thread.sleep(sleepInterval)
+        } catch {
+          case e: InterruptedException =>
+            logInfo("Interrupted during migration, will not refresh migrations.")
+            stopped = true
+          case NonFatal(e) =>
+            logError("Error occurred while trying to replicate for block manager decommissioning.",
+              e)
+            stopped = true
+        }
+      }
+    }
+  }
+
+  private lazy val shuffleBlockMigrationRefreshExecutor =
+    ThreadUtils.newDaemonSingleThreadExecutor("block-manager-decommission-shuffle")
+
+  private val shuffleBlockMigrationRefreshRunnable = new Runnable {
+    val sleepInterval = conf.get(config.STORAGE_DECOMMISSION_REPLICATION_REATTEMPT_INTERVAL)
+
+    override def run() {
+      assert(conf.get(config.STORAGE_DECOMMISSION_SHUFFLE_BLOCKS_ENABLED))
+      while (!stopped && !Thread.interrupted()) {
+        try {
+          logDebug("Attempting to replicate all shuffle blocks")
+          refreshOffloadingShuffleBlocks()
+          logInfo("Done starting workers to migrate shuffle blocks")
+          Thread.sleep(sleepInterval)
+        } catch {
+          case e: InterruptedException =>
+            logInfo("Interrupted during migration, will not refresh migrations.")
+            stopped = true
+          case NonFatal(e) =>
+            logError("Error occurred while trying to replicate for block manager decommissioning.",
+              e)
+            stopped = true
+        }
+      }
+    }
+  }
+
+  lazy val shuffleMigrationPool = ThreadUtils.newDaemonCachedThreadPool(
+    "migrate-shuffles",
+    conf.get(config.STORAGE_DECOMMISSION_SHUFFLE_MAX_THREADS))
+
+  /**
+   * Tries to offload all shuffle blocks that are registered with the shuffle service locally.
+   * Note: this does not delete the shuffle files in-case there is an in-progress fetch
+   * but rather shadows them.
+   * Requires an Indexed based shuffle resolver.
+   * Note: if called in testing please call stopOffloadingShuffleBlocks to avoid thread leakage.
+   */
+  private[storage] def refreshOffloadingShuffleBlocks(): Unit = {
+    // Update the queue of shuffles to be migrated
+    logInfo("Offloading shuffle blocks")
+    val localShuffles = bm.migratableResolver.getStoredShuffles()
+    val newShufflesToMigrate = localShuffles.diff(migratingShuffles).toSeq
+    shufflesToMigrate.addAll(newShufflesToMigrate.map(x => (x, 0)).asJava)
+    migratingShuffles ++= newShufflesToMigrate
+
+    // Update the threads doing migrations
+    val livePeerSet = bm.getPeers(false).toSet
+    val currentPeerSet = migrationPeers.keys.toSet
+    val deadPeers = currentPeerSet.diff(livePeerSet)
+    val newPeers = livePeerSet.diff(currentPeerSet)
+    migrationPeers ++= newPeers.map { peer =>
+      logDebug(s"Starting thread to migrate shuffle blocks to ${peer}")
+      val runnable = new ShuffleMigrationRunnable(peer)
+      shuffleMigrationPool.submit(runnable)
+      (peer, runnable)
+    }
+    // A peer may have entered a decommissioning state, don't transfer any new blocks
+    deadPeers.foreach { peer =>
+        migrationPeers.get(peer).foreach(_.running = false)
+    }
+  }
+
+  /**
+   * Stop migrating shuffle blocks.
+   */
+  private[storage] def stopOffloadingShuffleBlocks(): Unit = {
+    logInfo("Stopping offloading shuffle blocks.")
+    // Stop as gracefully as possible.
+    migrationPeers.values.foreach{_.running = false}

Review comment:
       nit: space before _ ? 

##########
File path: core/src/main/scala/org/apache/spark/storage/BlockManager.scala
##########
@@ -650,6 +662,23 @@ private[spark] class BlockManager(
       blockId: BlockId,
       level: StorageLevel,
       classTag: ClassTag[_]): StreamCallbackWithID = {
+
+    if (isDecommissioning()) {
+       throw new BlockSavedOnDecommissionedBlockManagerException(blockId)
+    }
+
+    if (blockId.isShuffle) {
+      logInfo(s"Putting shuffle block ${blockId}")

Review comment:
       Could this and line on 680 blow up ? Should we make this logDebug ?




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