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Sylvain Lebresne commented on CASSANDRA-3569:
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bq. But given that we are using TCP, it's not adding anything, it seems to me,
except for the fact that the FD is more tweakable (from the app) than the
keep-alive timeouts.
That's not the definition of being orthogonal in my book, but ok. I'll also
note that the FD mostly pretend to adapt to the network condition (whether it
does that well or not is another question). I don't think anybody ever
pretended it was handling the connectivity to other nodes better that TCP.
Besides, the FD is also here to detect node failures even when we're not
actively communicating with them. But yes, this is not the case for streaming
and yes for streaming, the FD don't add much value. And I agree, keep-alive is
probably better for that case. I'm merely disagreeing that for that case the
FD removes so much value that it's 'non-sensicle' (given it's already there
that is).
Anyway, in case that wasn't clear I'm not opposed to your proposition so please
feel free to submit a patch.
> Failure detector downs should not break streams
> -----------------------------------------------
>
> Key: CASSANDRA-3569
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3569
> Project: Cassandra
> Issue Type: Bug
> Reporter: Peter Schuller
> Assignee: Peter Schuller
>
> 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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