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From "Jeff Jirsa (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-13095) Timeouts between nodes
Date Thu, 22 Jun 2017 02:07:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-13095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16058605#comment-16058605
] 

Jeff Jirsa commented on CASSANDRA-13095:
----------------------------------------

Believe this is a dupe of CASSANDRA-13159 - you reported it first, but I somehow saw that
patch first.
 [~d.smirnov] agree? 

> Timeouts between nodes
> ----------------------
>
>                 Key: CASSANDRA-13095
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13095
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Danil Smirnov
>            Assignee: Danil Smirnov
>            Priority: Minor
>         Attachments: 13095-2.1.patch
>
>
> Recently I've run into a problem with heavily loaded cluster when sometimes messages
between certain nodes become blocked with no reason.
> It looks like the same situation that described here https://issues.apache.org/jira/browse/CASSANDRA-12676?focusedCommentId=15736166&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15736166
> Thread dump showed infinite loop here: https://github.com/apache/cassandra/blob/a8a43dd32eb92406d7d8b105e08c68b3d5c7df49/src/java/org/apache/cassandra/utils/CoalescingStrategies.java#L109
> Apparently the problem is in the initial value of epoch filed in TimeHorizonMovingAverageCoalescingStrategy
class. When it's value is not evenly divisible by BUCKET_INTERVAL, ix(epoch-1) does not point
to the correct bucket. As a result, sum gradually increases and, upon reaching MEASURED_INTERVAL,
averageGap becomes 0 and thread blocks.
> It's hard to reproduce because it takes a long time for sum to grow and when no messages
are send for some time, sum becomes 0 https://github.com/apache/cassandra/blob/a8a43dd32eb92406d7d8b105e08c68b3d5c7df49/src/java/org/apache/cassandra/utils/CoalescingStrategies.java#L301
and bug is no longer reproducible (until connection between nodes is re-created).
> I've added a patch which should fix the problem. Don't know if it would be of any help
since CASSANDRA-12676 will apparently disable this behaviour. One note about performance regressions
though. There is a small chance it being result of the bug described here, so it might be
worth testing performance after fixes and/or tuning the algorithm.



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