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Re: [Linux-cluster] Add option SO_LINGER to dlm sctp socket when the other endpoint is down.



(I sent this before, but the mail wasn't going through. Trying again.
Sorry for a possible duplicate.)

On 2013-11-13T12:24:49, David Teigland <teigland redhat com> wrote:

> There are significant subtleties involved in using SO_LINGER with tcp.
> I do not know whether applying it here would be good or bad in the tcp
> case, much less the sctp case.  I assume that the default tcp/sctp
> behavior exists for some good reasons, and I'd like any change to be
> reviewed by experts in the area.

That'd be awesome. I wonder if we can find some? ;-)

The goal here is that we know the other endpoint is down (we received a
node down event and have completed fencing at that stage). Hence,
SO_LINGER to speed up the shutdown of the socket seems appropriate.

See
http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable

And for SCTP it is the same:

http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-01#section-7.1.4

(We may actually only want to set SO_LINGER for the node down event
case, not generally. On receiving node down, set SO_LINGER as described
here. Otherwise, we may hit the corner cases in the first reference; but
we're already exposed to that today.)

> We do not want to risk harming any common situations for the sake of
> this uncommon and avoidable one.

I really would love to know how we can avoid it. We have a few customers
who can reproduce this.


Regards,
    Lars

-- 
Architect Storage/HA
SUSE LINUX Products GmbH, GF: Jeff Hawn, Jennifer Guild, Felix Imend├Ârffer, HRB 21284 (AG N├╝rnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde


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