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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4066) Cassandra cluster stops responding on time change (scheduling not using monotonic time?)
Date Mon, 02 Jul 2012 16:27:22 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13405110#comment-13405110
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Jonathan Ellis commented on CASSANDRA-4066:
-------------------------------------------

To summarize:

The linux kernel bug causes livelock when ntp moves the clock backwards.  This manifests with
nodes showing super high load for no [other] reason and marking each other down as Herman
points out, both on Java systems like C*/Hadoop/ElasticSearch and non-Java systems like mysql.
 It does NOT cause the kind of GossipTask death Brandon talks about in the first part of the
ticket, which you only need to worry about if you're changing time by a lot more than a leap
second.

The former you can fix by upgrading to a fixed linux kernel before the next leap second in
a few years, or by rebooting or applying {{date; date `date +"%m%d%H%M%C%y.%S"`; date}} when
you get bitten.  The latter is not worth addressing since it only applies to VMs that get
hibernated.

                
> Cassandra cluster stops responding on time change (scheduling not using monotonic time?)

> -----------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-4066
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4066
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: Linux; CentOS6 2.6.32-220.4.2.el6.x86_64
>            Reporter: David Daeschler
>            Assignee: Brandon Williams
>            Priority: Minor
>              Labels: gossip
>             Fix For: 1.1.1
>
>
> The server installation I set up did not have ntpd installed in the base installation.
When I noticed that the clocks were skewing I installed ntp and set the date on all the servers
in the cluster. A short time later, I started getting UnavailableExceptions on the clients.

> Also, one sever seemed to be unaffected by the time change. That server happened to have
it's time pushed forward, not backwards like the other 3 in the cluster. This leads me to
believe something is running on a timer/schedule that is not monotonic.
> I'm posting this as a bug, but I suppose it might just be part of the communication protocols
etc for the cluster and part of the design. But I think the devs should be aware of what I
saw.
> Otherwise, thank you for a fantastic product. Even after restarting 75% of the cluster
things seem to have recovered nicely.

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