Github user andrewor14 commented on a diff in the pull request:

    https://github.com/apache/spark/pull/126#discussion_r10543007
  
    --- Diff: core/src/main/scala/org/apache/spark/ContextCleaner.scala ---
    @@ -0,0 +1,126 @@
    +/*
    + * 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 scala.collection.mutable.{ArrayBuffer, SynchronizedBuffer}
    +
    +import java.util.concurrent.{LinkedBlockingQueue, TimeUnit}
    +
    +import org.apache.spark.rdd.RDD
    +
    +/** Listener class used for testing when any item has been cleaned by the 
Cleaner class */
    +private[spark] trait CleanerListener {
    +  def rddCleaned(rddId: Int)
    +  def shuffleCleaned(shuffleId: Int)
    +}
    +
    +/**
    + * Cleans RDDs and shuffle data.
    + */
    +private[spark] class ContextCleaner(env: SparkEnv) extends Logging {
    +
    +  /** Classes to represent cleaning tasks */
    +  private sealed trait CleaningTask
    +  private case class CleanRDD(sc: SparkContext, id: Int) extends 
CleaningTask
    +  private case class CleanShuffle(id: Int) extends CleaningTask
    +  // TODO: add CleanBroadcast
    +
    +  private val queue = new LinkedBlockingQueue[CleaningTask]
    +
    +  protected val listeners = new ArrayBuffer[CleanerListener]
    +    with SynchronizedBuffer[CleanerListener]
    +
    +  private val cleaningThread = new Thread() { override def run() { 
keepCleaning() }}
    +
    +  private var stopped = false
    +
    +  /** Start the cleaner */
    +  def start() {
    +    cleaningThread.setDaemon(true)
    +    cleaningThread.start()
    +  }
    +
    +  /** Stop the cleaner */
    +  def stop() {
    +    synchronized { stopped = true }
    +    cleaningThread.interrupt()
    +  }
    +
    +  /** Clean (unpersist) RDD data. */
    +  def cleanRDD(rdd: RDD[_]) {
    +    enqueue(CleanRDD(rdd.sparkContext, rdd.id))
    +    logDebug("Enqueued RDD " + rdd + " for cleaning up")
    +  }
    +
    +  /** Clean shuffle data. */
    +  def cleanShuffle(shuffleId: Int) {
    +    enqueue(CleanShuffle(shuffleId))
    +    logDebug("Enqueued shuffle " + shuffleId + " for cleaning up")
    +  }
    +
    +  def attachListener(listener: CleanerListener) {
    +    listeners += listener
    +  }
    +  /** Enqueue a cleaning task */
    +  private def enqueue(task: CleaningTask) {
    +    queue.put(task)
    +  }
    +
    +  /** Keep cleaning RDDs and shuffle data */
    +  private def keepCleaning() {
    +    try {
    +      while (!isStopped) {
    +        val taskOpt = Option(queue.poll(100, TimeUnit.MILLISECONDS))
    +        if (taskOpt.isDefined) {
    +          logDebug("Got cleaning task " + taskOpt.get)
    +          taskOpt.get match {
    +            case CleanRDD(sc, rddId) => doCleanRDD(sc, rddId)
    +            case CleanShuffle(shuffleId) => doCleanShuffle(shuffleId)
    +          }
    +        }
    +      }
    +    } catch {
    +      case ie: java.lang.InterruptedException =>
    +        if (!isStopped) logWarning("Cleaning thread interrupted")
    +    }
    +  }
    +
    +  /** Perform RDD cleaning */
    +  private def doCleanRDD(sc: SparkContext, rddId: Int) {
    +    logDebug("Cleaning rdd " + rddId)
    +    sc.env.blockManager.master.removeRdd(rddId, false)
    +    sc.persistentRdds.remove(rddId)
    --- End diff --
    
    It seems that if one of these throws an exception, then that can crash your 
cleaning thread, since ```keepCleaning``` only catches InterruptedException. 
Either add a try catch here and in ```doCleanShuffle```, or within the while 
loop of ```keepCleaning```.


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