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https://issues.apache.org/jira/browse/CASSANDRA-14674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16621555#comment-16621555
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Jeff Jirsa edited comment on CASSANDRA-14674 at 9/20/18 6:07 AM:
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{quote}Is this causing any problems for you? An occasional hung thread isn't
ideal, but I don't think this affects correctness.{quote}
I'm not sure if this is the scenario I recall, but there exists at least one
scenario like this (in 2.1) where you end up unable to run any repairs until
you bounce the host, because the {{executor}} in {{ActiveRepairService}} is
started with
[4|https://github.com/apache/cassandra/blob/cassandra-2.1/src/java/org/apache/cassandra/service/ActiveRepairService.java#L94]
threads, and if you get 4 stuck threads, you're broken forever.
was (Author: jjirsa):
{quote}Is this causing any problems for you? An occasional hung thread isn't
ideal, but I don't think this affects correctness.{quote}
I'm not sure if this is the scenario I recall, but there exists at least one
scenario like this (in 2.1) where you end up unable to run any repairs until
you bounce the host, because {{ActiveRepairService}} is started with
[4|https://github.com/apache/cassandra/blob/cassandra-2.1/src/java/org/apache/cassandra/service/ActiveRepairService.java#L94]
threads, and if you get 4 stuck threads, you're broken forever.
> Repair Validation message request could get stuck forever at sender side
> ------------------------------------------------------------------------
>
> Key: CASSANDRA-14674
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14674
> Project: Cassandra
> Issue Type: Bug
> Components: Repair
> Reporter: Jaydeepkumar Chovatia
> Assignee: Jaydeepkumar Chovatia
> Priority: Major
>
> Validation request message as part of repair are currently sent as
> [sendOneWay|https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/repair/ValidationTask.java#L56]
> and then it waits at
> [Futures.getUnchecked|https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/repair/RepairJob.java#L160].
> If sender doesn’t hear back from receiver for whatever reason then thread is
> blocked forever. I’ve reproduced following stack trace at sender side by
> deliberately ignoring
> [VALIDATION_REQUST|https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/repair/RepairMessageVerbHandler.java#L114]
> at receiver side.
> {quote}"Repair#1:1" #301 daemon prio=5 os_prio=0 tid=0x00007f5a62060800
> nid=0x13198 waiting on condition [0x00007f5a5cc6c000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> parking to wait for <0x00000005c6ba9630> (a
> com.google.common.util.concurrent.AbstractFuture$Sync)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
> at
> com.google.common.util.concurrent.AbstractFuture$Sync.get(AbstractFuture.java:285)
> at
> com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:116)
> at
> com.google.common.util.concurrent.Uninterruptibles.getUninterruptibly(Uninterruptibles.java:137)
> at com.google.common.util.concurrent.Futures.getUnchecked(Futures.java:1509)
> at org.apache.cassandra.repair.RepairJob.run(RepairJob.java:160)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at
> org.apache.cassandra.concurrent.NamedThreadFactory.lambda$threadLocalDeallocator$0(NamedThreadFactory.java:79)
> at
> org.apache.cassandra.concurrent.NamedThreadFactory$$Lambda$3/1858015030.run(Unknown
> Source)
> at java.lang.Thread.run(Thread.java:745)
> {quote}
> AFAIK we should be using {{sendRR}} for this instead of {{sendOneWay}}.
> Please let me know if my understanding is correct or not.
> I am working on a fix to make it {{sendRR}}.
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