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https://issues.apache.org/jira/browse/SPARK-16379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15363013#comment-15363013
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Michael Gummelt commented on SPARK-16379:
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I traced back the addition of the `synchronized` block, and it seems Matei
added it a long time ago. I can't prove that the method is thread-safe, so I'd
rather not remove the synchronization block. So we can either:
1) Remove the log statements (I'd like to keep them)
2) Revert the `lazy` commit
3) Introduce an explicit lock, and synchronize on that rather than `this`
2) is the "correct" thing to do, since it's the author's responsibility to not
break existing code, but I'm OK with 3) as well. [~srowen] what do you think?
> Spark on mesos is broken due to race condition in Logging
> ---------------------------------------------------------
>
> Key: SPARK-16379
> URL: https://issues.apache.org/jira/browse/SPARK-16379
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 2.0.0
> Reporter: Stavros Kontopoulos
> Priority: Blocker
> Attachments: out.txt
>
>
> This commit introduced a transient lazy log val:
> https://github.com/apache/spark/commit/044971eca0ff3c2ce62afa665dbd3072d52cbbec
> This has caused problems in the past:
> https://github.com/apache/spark/pull/1004
> One commit before that everything works fine.
> I spotted that when my CI started to fail:
> https://ci.typesafe.com/job/mit-docker-test-ref/191/
> You can easily verify it by installing mesos on your machine and try to
> connect with spark shell from bin dir:
> ./spark-shell --master mesos://zk://localhost:2181/mesos --conf
> spark.executor.url=$(pwd)/../spark-2.0.0-SNAPSHOT-bin-test.tgz
> It gets stuck at the point where it tries to create the SparkContext.
> Logging gets stuck here:
> I0705 12:10:10.076617 9303 group.cpp:700] Trying to get
> '/mesos/json.info_0000000152' in ZooKeeper
> I0705 12:10:10.076920 9304 detector.cpp:479] A new leading master
> (UPID=master@127.0.1.1:5050) is detected
> I0705 12:10:10.076956 9303 sched.cpp:326] New master detected at
> master@127.0.1.1:5050
> I0705 12:10:10.077057 9303 sched.cpp:336] No credentials provided.
> Attempting to register without authentication
> I0705 12:10:10.090709 9301 sched.cpp:703] Framework registered with
> 13553f8b-f42c-4f20-88cd-16f1cc153ede-0001
> I verified it also by changing @transient lazy val log to def and it works as
> expected.
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