Make broadcast future package-private and add a flag allowing to check if it is initialized #156
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…k if it is initialized
markhamstra
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Feb 29, 2016
Make broadcast future package-private and add a flag allowing to check if it is initialized
markhamstra
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Apr 27, 2016
CheckpointWriter.stop() is prone to a race condition: if one thread calls `stop()` right as a checkpoint write task begins to execute, that write task may become blocked when trying to access `fs`, the shared Hadoop FileSystem, since both the `fs` getter and `stop` method synchronize on the same lock. Here's a thread-dump excerpt which illustrates the problem: ```java "pool-31-thread-1" alteryx#156 prio=5 os_prio=31 tid=0x00007fea02cd2000 nid=0x5c0b waiting for monitor entry [0x000000013bc4c000] java.lang.Thread.State: BLOCKED (on object monitor) at org.apache.spark.streaming.CheckpointWriter.org$apache$spark$streaming$CheckpointWriter$$fs(Checkpoint.scala:302) - waiting to lock <0x00000007bf53ee78> (a org.apache.spark.streaming.CheckpointWriter) at org.apache.spark.streaming.CheckpointWriter$CheckpointWriteHandler.run(Checkpoint.scala:224) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) "pool-1-thread-1-ScalaTest-running-MapWithStateSuite" alteryx#11 prio=5 os_prio=31 tid=0x00007fe9ff879800 nid=0x5703 waiting on condition [0x000000012e54c000] java.lang.Thread.State: TIMED_WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000007bf564568> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078) at java.util.concurrent.ThreadPoolExecutor.awaitTermination(ThreadPoolExecutor.java:1465) at org.apache.spark.streaming.CheckpointWriter.stop(Checkpoint.scala:291) - locked <0x00000007bf53ee78> (a org.apache.spark.streaming.CheckpointWriter) at org.apache.spark.streaming.scheduler.JobGenerator.stop(JobGenerator.scala:159) - locked <0x00000007bf53ea90> (a org.apache.spark.streaming.scheduler.JobGenerator) at org.apache.spark.streaming.scheduler.JobScheduler.stop(JobScheduler.scala:115) - locked <0x00000007bf53d3f0> (a org.apache.spark.streaming.scheduler.JobScheduler) at org.apache.spark.streaming.StreamingContext$$anonfun$stop$1.apply$mcV$sp(StreamingContext.scala:680) at org.apache.spark.util.Utils$.tryLogNonFatalError(Utils.scala:1219) at org.apache.spark.streaming.StreamingContext.stop(StreamingContext.scala:679) - locked <0x00000007bf516a70> (a org.apache.spark.streaming.StreamingContext) at org.apache.spark.streaming.StreamingContext.stop(StreamingContext.scala:644) - locked <0x00000007bf516a70> (a org.apache.spark.streaming.StreamingContext) [...] ``` We can fix this problem by having `stop` and `fs` be synchronized on different locks: the synchronization on `stop` only needs to guard against multiple threads calling `stop` at the same time, whereas the synchronization on `fs` is only necessary for cross-thread visibility. There's only ever a single active checkpoint writer thread at a time, so we don't need to guard against concurrent access to `fs`. Thus, `fs` can simply become a `volatile` var, similar to `lastCheckpointTime`. This change should fix [SPARK-13693](https://issues.apache.org/jira/browse/SPARK-13693), a flaky `MapWithStateSuite` test suite which has recently been failing several times per day. It also results in a huge test speedup: prior to this patch, `MapWithStateSuite` took about 80 seconds to run, whereas it now runs in less than 10 seconds. For the `streaming` project's tests as a whole, they now run in ~220 seconds vs. ~354 before. /cc zsxwing and tdas for review. Author: Josh Rosen <[email protected]> Closes apache#12712 from JoshRosen/fix-checkpoint-writer-race.
markhamstra
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Nov 7, 2017
* Exclude SparkSubmitSuite from Travis unit test build * Remove SortShuffleSuite * Exclude Java tests
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