External Group By to handle huge keys #18
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,49 @@ | ||
| /* | ||
| * 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 | ||
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| import java.io.File | ||
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| import org.apache.spark.util.cleanup.{CleanupTask, CleanExternalList} | ||
| import org.apache.spark.util.collection.ExternalList | ||
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| /** | ||
| * Asynchronous cleaner for objects created on the Executor. So far | ||
| * only supports cleaning up ExternalList objects. Equivalent to ContextCleaner | ||
| * but for objects on the Executor heap. | ||
| */ | ||
| private[spark] class ExecutorCleaner extends WeakReferenceCleaner { | ||
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| def registerExternalListForCleanup(list: ExternalList[_]): Unit = { | ||
| registerForCleanup(list, CleanExternalList(list.getBackingFileLocations())) | ||
| } | ||
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| def doCleanExternalList(paths: Iterable[String]): Unit = { | ||
| paths.map(path => new File(path)).foreach(f => { | ||
| if (f.exists()) f.delete() | ||
| }) | ||
| } | ||
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| override protected def handleCleanupForSpecificTask(task: CleanupTask): Unit = { | ||
| task match { | ||
| case CleanExternalList(paths) => doCleanExternalList(paths) | ||
| case unknown => logWarning(s"Got cleanup task that cannot be handled by ExecutorCleaner: $unknown") | ||
| } | ||
| } | ||
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| override protected def cleanupThreadName(): String = "Executor Cleaner" | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| /* | ||
| * 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 | ||
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| import java.lang.ref.ReferenceQueue | ||
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| import scala.collection.mutable.{ArrayBuffer, SynchronizedBuffer} | ||
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| import org.apache.spark.util.cleanup.{CleanupTask, CleanupTaskWeakReference} | ||
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| /** | ||
| * Utility trait that keeps a long running thread for cleaning up weak references | ||
| * after they are GCed. Currently implemented by ContextCleaner and ExecutorCleaner | ||
| * only. | ||
| */ | ||
| private[spark] trait WeakReferenceCleaner extends Logging { | ||
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| private val referenceBuffer = new ArrayBuffer[CleanupTaskWeakReference] | ||
| with SynchronizedBuffer[CleanupTaskWeakReference] | ||
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| private val referenceQueue = new ReferenceQueue[AnyRef] | ||
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| private val cleaningThread = new Thread() { override def run() { keepCleaning() }} | ||
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| private var stopped = false | ||
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| /** Start the cleaner. */ | ||
| def start(): Unit = { | ||
| cleaningThread.setDaemon(true) | ||
| cleaningThread.setName(cleanupThreadName()) | ||
| cleaningThread.start() | ||
| } | ||
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| def stop(): Unit = { | ||
| stopped = true | ||
| synchronized { | ||
| // Interrupt the cleaning thread, but wait until the current task has finished before | ||
| // doing so. This guards against the race condition where a cleaning thread may | ||
| // potentially clean similarly named variables created by a different SparkContext, | ||
| // resulting in otherwise inexplicable block-not-found exceptions (SPARK-6132). | ||
| cleaningThread.interrupt() | ||
| } | ||
| cleaningThread.join() | ||
| } | ||
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| protected def keepCleaning(): Unit = { | ||
| while (!stopped) { | ||
| try { | ||
| val reference = Option(referenceQueue.remove(WeakReferenceCleaner.REF_QUEUE_POLL_TIMEOUT)) | ||
| .map(_.asInstanceOf[CleanupTaskWeakReference]) | ||
| // Synchronize here to avoid being interrupted on stop() | ||
| synchronized { | ||
| reference.map(_.task).foreach { task => | ||
| logDebug("Got cleaning task " + task) | ||
| referenceBuffer -= reference.get | ||
| handleCleanupForSpecificTask(task) | ||
| } | ||
| } | ||
| } catch { | ||
| case ie: InterruptedException if stopped => // ignore | ||
| case e: Exception => logError("Error in cleaning thread", e) | ||
| } | ||
| } | ||
| } | ||
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| /** Register an object for cleanup. */ | ||
| protected def registerForCleanup(objectForCleanup: AnyRef, task: CleanupTask): Unit = { | ||
| referenceBuffer += new CleanupTaskWeakReference(task, objectForCleanup, referenceQueue) | ||
| } | ||
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| protected def handleCleanupForSpecificTask(task: CleanupTask) | ||
| protected def cleanupThreadName(): String | ||
| } | ||
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| private object WeakReferenceCleaner { | ||
| private val REF_QUEUE_POLL_TIMEOUT = 100 | ||
| } |
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Generally this is frowned upon, because foreach could possibly implemented in a parallel way, leading to concurrency issues if c1 isn't thread safe. I think in this case, we should be fine because c2 is not a parallel collection but just flagging the pattern.
I think you can do this instead
http://www.scala-lang.org/api/current/index.html#scala.collection.generic.Growable@++=(xs:scala.collection.TraversableOnce[A]):Growable.this.type
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I have to define ++= on ExternalList to do this. Which is doable, just it wasn't done.