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From "Christian Esken (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-13265) Expiration in OutboundTcpConnection can block the reader Thread
Date Wed, 08 Mar 2017 16:12:38 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-13265?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15901414#comment-15901414
] 

Christian Esken edited comment on CASSANDRA-13265 at 3/8/17 4:12 PM:
---------------------------------------------------------------------

I will update the status while working on the individual topics:
(x)    This needs to be configurable from the YAML and via JMX. 
(/)    It should include drained messages as well.
(/)    Typo, "thus letting"
(/)    Extra line break
(/)    We don't do/allow author tags
(/)    Use TimeUnit
  => Additionally I am now determining the timeout value automatic
(/)    It isn't using the constant.
(/)    Just in case maybe assert the droppable/non-droppable status of the verbs. Or does
it not matter since the tests will fail anyways?
   => It wouldn't matter, but I added a check make it more explicit.



was (Author: cesken):
I will update the status while working on the individual topics:
(x)    This needs to be configurable from the YAML and via JMX. 
(/)    It should include drained messages as well.
(/)    Typo, "thus letting"
(/)    Extra line break
(/)    We don't do/allow author tags
(/)    Use TimeUnit
(/)    It isn't using the constant.
(x)    Just in case maybe assert the droppable/non-droppable status of the verbs. Or does
it not matter since the tests will fail anyways?



> Expiration in OutboundTcpConnection can block the reader Thread
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-13265
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13265
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: Cassandra 3.0.9
> Java HotSpot(TM) 64-Bit Server VM version 25.112-b15 (Java version 1.8.0_112-b15)
> Linux 3.16
>            Reporter: Christian Esken
>            Assignee: Christian Esken
>         Attachments: cassandra.pb-cache4-dus.2017-02-17-19-36-26.chist.xz, cassandra.pb-cache4-dus.2017-02-17-19-36-26.td.xz
>
>
> I observed that sometimes a single node in a Cassandra cluster fails to communicate to
the other nodes. This can happen at any time, during peak load or low load. Restarting that
single node from the cluster fixes the issue.
> Before going in to details, I want to state that I have analyzed the situation and am
already developing a possible fix. Here is the analysis so far:
> - A Threaddump in this situation showed  324 Threads in the OutboundTcpConnection class
that want to lock the backlog queue for doing expiration.
> - A class histogram shows 262508 instances of OutboundTcpConnection$QueuedMessage.
> What is the effect of it? As soon as the Cassandra node has reached a certain amount
of queued messages, it starts thrashing itself to death. Each of the Thread fully locks the
Queue for reading and writing by calling iterator.next(), making the situation worse and worse.
> - Writing: Only after 262508 locking operation it can progress with actually writing
to the Queue.
> - Reading: Is also blocked, as 324 Threads try to do iterator.next(), and fully lock
the Queue
> This means: Writing blocks the Queue for reading, and readers might even be starved which
makes the situation even worse.
> -----
> The setup is:
>  - 3-node cluster
>  - replication factor 2
>  - Consistency LOCAL_ONE
>  - No remote DC's
>  - high write throughput (100000 INSERT statements per second and more during peak times).
>  



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