Github user squito commented on a diff in the pull request:
https://github.com/apache/spark/pull/19041#discussion_r178967087
--- Diff: core/src/main/scala/org/apache/spark/CacheRecoveryManager.scala
---
@@ -0,0 +1,201 @@
+/*
+ * 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
+
+import java.util.concurrent.TimeUnit
+
+import scala.collection.JavaConverters._
+import scala.concurrent.{ExecutionContext, Future, Promise}
+import scala.util.Failure
+
+import com.google.common.cache.CacheBuilder
+
+import org.apache.spark.CacheRecoveryManager.{DoneRecovering, KillReason,
Timeout}
+import org.apache.spark.internal.Logging
+import
org.apache.spark.internal.config.DYN_ALLOCATION_CACHE_RECOVERY_TIMEOUT
+import org.apache.spark.rpc.RpcEndpointRef
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.storage.BlockManagerMessages._
+import org.apache.spark.util.ThreadUtils
+
+/**
+ * Responsible for asynchronously replicating all of an executor's cached
blocks, and then shutting
+ * it down.
+ */
+private class CacheRecoveryManager(
+ blockManagerMasterEndpoint: RpcEndpointRef,
+ executorAllocationManager: ExecutorAllocationManager,
+ conf: SparkConf)
+ extends Logging {
+
+ private val forceKillAfterS =
conf.get(DYN_ALLOCATION_CACHE_RECOVERY_TIMEOUT)
+ private val threadPool =
ThreadUtils.newDaemonCachedThreadPool("cache-recovery-manager-pool")
+ private implicit val asyncExecutionContext =
ExecutionContext.fromExecutorService(threadPool)
+ private val scheduler =
+
ThreadUtils.newDaemonSingleThreadScheduledExecutor("cache-recovery-shutdown-timers")
+ private val recoveringExecutors = CacheBuilder.newBuilder()
+ .expireAfterWrite(forceKillAfterS * 2, TimeUnit.SECONDS)
+ .build[String, String]()
+
+ /**
+ * Start the recover cache shutdown process for these executors
+ *
+ * @param execIds the executors to start shutting down
+ * @return a sequence of futures of Unit that will complete once the
executor has been killed.
+ */
+ def startCacheRecovery(execIds: Seq[String]): Future[Seq[KillReason]] = {
+ logDebug(s"Recover cached data before shutting down executors
${execIds.mkString(", ")}.")
+ val canBeRecovered: Future[Seq[String]] = checkMem(execIds)
+
+ canBeRecovered.flatMap { execIds =>
+ execIds.foreach { execId => recoveringExecutors.put(execId, execId) }
+ Future.sequence(execIds.map { replicateUntilTimeoutThenKill })
+ }
+ }
+
+ def replicateUntilTimeoutThenKill(execId: String): Future[KillReason] = {
+ val timeoutFuture = returnAfterTimeout(Timeout, forceKillAfterS)
+ val replicationFuture = replicateUntilDone(execId)
+
+ Future.firstCompletedOf(List(timeoutFuture,
replicationFuture)).andThen {
+ case scala.util.Success(DoneRecovering) =>
+ logTrace(s"Done recovering blocks on $execId, killing now")
+ case scala.util.Success(Timeout) =>
+ logWarning(s"Couldn't recover cache on $execId before
$forceKillAfterS second timeout")
+ case Failure(ex) =>
+ logWarning(s"Error recovering cache on $execId", ex)
+ }.andThen {
+ case _ =>
+ kill(execId)
+ }
+ }
+
+ /**
+ * Given a list of executors that will be shut down, check if there is
enough free memory on the
+ * rest of the cluster to hold their data. Return a list of just the
executors for which there
+ * will be enough space. Executors are included smallest first.
+ *
+ * This is a best guess implementation and it is not guaranteed that all
returned executors
+ * will succeed. For example a block might be too big to fit on any one
specific executor.
+ *
+ * @param execIds executors which will be shut down
+ * @return a Seq of the executors we do have room for
+ */
+ private def checkMem(execIds: Seq[String]): Future[Seq[String]] = {
+ val execsToShutDown = execIds.toSet
+ // Memory Status is a map of executor Id to a tuple of Max Memory and
remaining memory on that
+ // executor.
+ val futureMemStatusByBlockManager =
+ blockManagerMasterEndpoint.ask[Map[BlockManagerId, (Long,
Long)]](GetMemoryStatus)
+
+ val futureMemStatusByExecutor = futureMemStatusByBlockManager.map {
memStat =>
+ memStat.map { case (blockManagerId, mem) =>
blockManagerId.executorId -> mem }
+ }
+
+ futureMemStatusByExecutor.map { memStatusByExecutor =>
+ val (expiringMemStatus, remainingMemStatus) =
memStatusByExecutor.partition {
+ case (execId, _) => execsToShutDown.contains(execId)
+ }
+ val freeMemOnRemaining = remainingMemStatus.values.map(_._2).sum
+
+ // The used mem on each executor sorted from least used mem to
greatest
+ val executorAndUsedMem: Seq[(String, Long)] =
+ expiringMemStatus.map { case (execId, (maxMem, remainingMem)) =>
+ val usedMem = maxMem - remainingMem
+ execId -> usedMem
+ }.toSeq.sortBy { case (_, usedMem) => usedMem }
+
+ executorAndUsedMem
+ .scan(("start", freeMemOnRemaining)) {
+ case ((_, freeMem), (execId, usedMem)) => (execId, freeMem -
usedMem)
+ }
+ .drop(1)
+ .filter { case (_, freeMem) => freeMem > 0 }
+ .map(_._1)
+ }
+ }
+
+ /**
+ * Given a value and a timeout in seconds, complete the future with the
value when time is up.
+ *
+ * @param value The value to be returned after timeout period
+ * @param seconds the number of seconds to wait
+ * @return a future that will hold the value given after a timeout
+ */
+ private def returnAfterTimeout[T](value: T, seconds: Long): Future[T] = {
+ val p = Promise[T]()
+ val runnable = new Runnable {
+ def run(): Unit = { p.success(value) }
+ }
+ scheduler.schedule(runnable, seconds, TimeUnit.SECONDS)
+ p.future
+ }
+
+ /**
+ * Recover cached RDD blocks off of an executor until there are no more,
or until
+ * there is an error
+ *
+ * @param execId the id of the executor to be killed
+ * @return a Future of Unit that will complete once all blocks have been
replicated.
+ */
+ private def replicateUntilDone(execId: String): Future[KillReason] = {
--- End diff --
return type in doc is wrong
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