Repository: spark Updated Branches: refs/heads/master 2e069ca65 -> c9da466ed
[SPARK-3015] Block on cleaning tasks to prevent Akka timeouts More detail on the issue is described in [SPARK-3015](https://issues.apache.org/jira/browse/SPARK-3015), but the TLDR is if we send too many blocking Akka messages that are dependent on each other in quick successions, then we end up causing a few of these messages to time out and ultimately kill the executors. As of #1498, we broadcast each RDD whether or not it is persisted. This means if we create many RDDs (each of which becomes a broadcast) and the driver performs a GC that cleans up all of these broadcast blocks, then we end up sending many `RemoveBroadcast` messages in parallel and trigger the chain of blocking messages at high frequencies. We do not know of the Akka-level root cause yet, so this is intended to be a temporary solution until we identify the real issue. I have done some preliminary testing of enabling blocking and observed that the queue length remains quite low (< 1000) even under very intensive workloads. In the long run, we should do something more sophisticated to allow a limited degree of parallelism through batching clean up tasks or processing them in a sliding window. In the longer run, we should clean up the whole `BlockManager*` message passing interface to avoid unnecessarily awaiting on futures created from Akka asks. tdas pwendell mengxr Author: Andrew Or <[email protected]> Closes #1931 from andrewor14/reference-blocking and squashes the following commits: d0f7195 [Andrew Or] Merge branch 'master' of github.com:apache/spark into reference-blocking ce9daf5 [Andrew Or] Remove logic for logging queue length 111192a [Andrew Or] Add missing space in log message (minor) a183b83 [Andrew Or] Switch order of code blocks (minor) 9fd1fe6 [Andrew Or] Remove outdated log 104b366 [Andrew Or] Use the actual reference queue length 0b7e768 [Andrew Or] Block on cleaning tasks by default + log error on queue full Project: http://git-wip-us.apache.org/repos/asf/spark/repo Commit: http://git-wip-us.apache.org/repos/asf/spark/commit/c9da466e Tree: http://git-wip-us.apache.org/repos/asf/spark/tree/c9da466e Diff: http://git-wip-us.apache.org/repos/asf/spark/diff/c9da466e Branch: refs/heads/master Commit: c9da466edb83e45a159ccc17c68856a511b9e8b7 Parents: 2e069ca Author: Andrew Or <[email protected]> Authored: Fri Aug 15 22:55:32 2014 -0700 Committer: Patrick Wendell <[email protected]> Committed: Fri Aug 15 22:55:32 2014 -0700 ---------------------------------------------------------------------- .../main/scala/org/apache/spark/ContextCleaner.scala | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/spark/blob/c9da466e/core/src/main/scala/org/apache/spark/ContextCleaner.scala ---------------------------------------------------------------------- diff --git a/core/src/main/scala/org/apache/spark/ContextCleaner.scala b/core/src/main/scala/org/apache/spark/ContextCleaner.scala index bf3c3a6..3848734 100644 --- a/core/src/main/scala/org/apache/spark/ContextCleaner.scala +++ b/core/src/main/scala/org/apache/spark/ContextCleaner.scala @@ -66,10 +66,15 @@ private[spark] class ContextCleaner(sc: SparkContext) extends Logging { /** * Whether the cleaning thread will block on cleanup tasks. - * This is set to true only for tests. + * + * Due to SPARK-3015, this is set to true by default. This is intended to be only a temporary + * workaround for the issue, which is ultimately caused by the way the BlockManager actors + * issue inter-dependent blocking Akka messages to each other at high frequencies. This happens, + * for instance, when the driver performs a GC and cleans up all broadcast blocks that are no + * longer in scope. */ private val blockOnCleanupTasks = sc.conf.getBoolean( - "spark.cleaner.referenceTracking.blocking", false) + "spark.cleaner.referenceTracking.blocking", true) @volatile private var stopped = false @@ -174,9 +179,6 @@ private[spark] class ContextCleaner(sc: SparkContext) extends Logging { private def blockManagerMaster = sc.env.blockManager.master private def broadcastManager = sc.env.broadcastManager private def mapOutputTrackerMaster = sc.env.mapOutputTracker.asInstanceOf[MapOutputTrackerMaster] - - // Used for testing. These methods explicitly blocks until cleanup is completed - // to ensure that more reliable testing. } private object ContextCleaner { --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
