Github user vanzin commented on a diff in the pull request:
https://github.com/apache/spark/pull/19041#discussion_r163045008
--- Diff: core/src/main/scala/org/apache/spark/CacheRecoveryManager.scala
---
@@ -0,0 +1,187 @@
+/*
+ * 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.{ScheduledFuture, TimeUnit}
+
+import scala.collection.JavaConverters._
+import scala.concurrent.{ExecutionContext, Future}
+import scala.util.Failure
+
+import com.google.common.cache.CacheBuilder
+
+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.
+ */
+final 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 =
+ ExecutionContext.fromExecutorService(threadPool)
+ private val scheduler =
+
ThreadUtils.newDaemonSingleThreadScheduledExecutor("cache-recovery-shutdown-timers")
+ private val recoveringExecutors = CacheBuilder.newBuilder()
+ .expireAfterWrite(forceKillAfterS * 2, TimeUnit.SECONDS)
+ .build[String, java.lang.Boolean]() // Cache value never used and must
extend Object
+
+ /**
+ * Start the recover cache shutdown process for these executors
+ *
+ * @param execIds the executors to start shutting down
+ * @return a sequence of futures representing the kill process.
+ */
+ def startCacheRecovery(execIds: Seq[String]): Seq[Future[Boolean]] = {
+ logDebug(s"Recover cached data before shutting down executors
${execIds.mkString(", ")}.")
+ val canBeRecovered = checkMem(execIds)
+ canBeRecovered.foreach { execId => recoveringExecutors.put(execId,
true)}
+ canBeRecovered.map { execId =>
+ val killTimer = startKillTimer(execId)
+ replicateUntilDone(execId)
+ .andThen {
+ // don't log if kill timer is done, because it would be redundant
+ case Failure(e) if !killTimer.isDone =>
+ logWarning(s"Failure recovering cached data before executor
$execId shutdown", e)
+ }
+ .andThen {
+ case _ =>
+ if (killTimer.cancel(false)) { 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]): 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 allExecMemStatus: Map[String, (Long, Long)] =
blockManagerMasterEndpoint
+ .askSync[Map[BlockManagerId, (Long, Long)]](GetMemoryStatus)
--- End diff --
I'm a little worried about this call. It's called from a synchronized block
in the executor allocation manager, which means you'll block that object until
the RPC finishes.
It seems to be a process-local RPC, so it's faster, but this is still kind
of a sketchy thing to do (can it deadlock? can it take a while to finish? etc
etc).
Is there an easy way you could make the `startCacheRecovery` method
asynchronous?
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