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From "Christian Esken (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-13265) Expiration in OutboundTcpConnection can block the reader Thread
Date Mon, 24 Apr 2017 14:32:04 GMT


Christian Esken commented on CASSANDRA-13265:

First here is the summary: The tests work if I add "DatabaseDescriptor.daemonInitialization();"
to the unit test of the affected branches. Is this a good idea, [~aweisberg]?

Now the long story:

This is the status for branch cassandra-13265-3.0:
- (/) Running unit tests in Eclipse: Works
 - (/)/(?) CircleCI: All normal tests work fine. "Your build ran 4754 tests in junit with
0 failures".  The build fails for me with: Target "stress-test" does not exist in the project
"apache-cassandra". As "ant test" worked, I would guess that the patch is fine. I will reverify
the specific unit test locally

This is the status for branch cassandra-13265-3.11 and cassandra-13265-trunk:
- (/) Running unit tests in Eclipse: Works
- (x) Running unit tests with CircleCI or "ant test" fails, due to non-initialized DatabaseDescriptor.
  When I add the following to the unit test of cassandra-13265-3.11, the unit test works.


    [junit] Null Test:  Caused an ERROR
    [junit] null
    [junit] java.lang.ExceptionInInitializerError
    [junit]     at java.lang.Class.forName0(Native Method)
    [junit]     at java.lang.Class.forName(
    [junit] Caused by: java.lang.NullPointerException
    [junit]     at org.apache.cassandra.config.DatabaseDescriptor.getWriteRpcTimeout(
    [junit]     at$Verb$1.getTimeout(
    [junit]     at<clinit>(

> Expiration in OutboundTcpConnection can block the reader Thread
> ---------------------------------------------------------------
>                 Key: CASSANDRA-13265
>                 URL:
>             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
>             Fix For: 3.0.x
>         Attachments: cassandra.pb-cache4-dus.2017-02-17-19-36-26.chist.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, 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, 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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