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From "Joshua McKenzie (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3569) Failure detector downs should not break streams
Date Wed, 14 May 2014 17:47:21 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3569?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13997806#comment-13997806
] 

Joshua McKenzie commented on CASSANDRA-3569:
--------------------------------------------

That's correct.  It's a little tricky to time it right since cable-yanking during Merkle-sync
means FD down kills it all, but I've managed to confirm that you can repeatedly block / unplug
the remote side if timed right, wait for FD down, plug it back in after about 20-30 seconds,
and things resume where they left off.

> Failure detector downs should not break streams
> -----------------------------------------------
>
>                 Key: CASSANDRA-3569
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3569
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Peter Schuller
>            Assignee: Joshua McKenzie
>             Fix For: 2.1.1
>
>         Attachments: 3569-2.0.txt, 3569_v1.txt
>
>
> CASSANDRA-2433 introduced this behavior just to get repairs to don't sit there waiting
forever. In my opinion the correct fix to that problem is to use TCP keep alive. Unfortunately
the TCP keep alive period is insanely high by default on a modern Linux, so just doing that
is not entirely good either.
> But using the failure detector seems non-sensicle to me. We have a communication method
which is the TCP transport, that we know is used for long-running processes that you don't
want to incorrectly be killed for no good reason, and we are using a failure detector tuned
to detecting when not to send real-time sensitive request to nodes in order to actively kill
a working connection.
> So, rather than add complexity with protocol based ping/pongs and such, I propose that
we simply just use TCP keep alive for streaming connections and instruct operators of production
clusters to tweak net.ipv4.tcp_keepalive_{probes,intvl} as appropriate (or whatever equivalent
on their OS).
> I can submit the patch. Awaiting opinions.



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