Open Stack

The patch has been merged finally, after a couple dozen rounds of codereview :)

Enjoy your H/A queues, fellow openstackers!

https://github.com/openstack/nova/commit/32b674b0abb338c82850fc24d39f9632c71503e6

On Thu, Aug 2, 2012 at 8:06 AM, Daniel He <csdhe.geek at gmail.com> wrote:
> Thanks a lot.
>
> Dan
>
>
> On 2 August 2012 16:02, Eugene Kirpichov <ekirpichov at gmail.com> wrote:
>>
>> The review is going on at https://review.openstack.org/#/c/10305/
>>
>> On Thu, Aug 2, 2012 at 12:31 AM, Daniel He <csdhe.geek at gmail.com> wrote:
>> > Hi Eugene,
>> >
>> > By the way, where is these patches I can download/checkout thanks
>> >
>> > Dan
>> >
>> > On 1 August 2012 23:01, Eugene Kirpichov <ekirpichov at gmail.com> wrote:
>> >>
>> >> Hi Andrea,
>> >>
>> >> I think you're right that it's necessary to react to cancel
>> >> notifications.
>> >> I'll address this in my patch.
>> >>
>> >> On Fri, Jul 27, 2012 at 7:05 AM, Rosa, Andrea (HP Cloud Services)
>> >> <andrea.rosa at hp.com> wrote:
>> >> > Hi
>> >> >
>> >> >>As for consumer cancellation notifications - I need to remember when
>> >> >>exactly they happen in an HA setup. Maybe you're right.
>> >> >
>> >> > With the HA active/active configuration clients always consume from
>> >> > the
>> >> > Master node so we can have a scenario where the queue is declared on
>> >> > a Slave
>> >> > node but the clients are consuming from the Master node.
>> >> > In this situation if the master node goes down the client doesn't get
>> >> > any error/exception from the connection and the consumer is abruptly
>> >> > disconnected, so the client needs to re-consume the queue (register a
>> >> > new
>> >> > consumer) to be able to get messages from the queue.
>> >> > The consumer cancellation notifications is a way for a client to get
>> >> > a
>> >> > notification (via a basic.cancel message) when the consumer has been
>> >> > disconnected.
>> >> >
>> >> > With the HA configuration we should care about of two things:
>> >> > 1 connection dying : this is already addressed by the existing code
>> >> > 2 basic.cancel notification received by the clients: in my opinion
>> >> > this
>> >> > is not yet addressed
>> >> >
>> >> >>As for duplicated messages - the situation here is no different
>> >> >>whether you have 1 or many rabbits; reconnection logic was already in
>> >> >>place. Perhaps something should be done here, but it seems that the
>> >> >>lack of this logic didn't hurt anyone so far. Maybe it is because
>> >> >> IIRC
>> >> >>messages are ack'd immediately and the failure window is very small.
>> >> >
>> >> > Yes you are absolutely right, but with the HA configuration is more
>> >> > likely to have retransmissions.
>> >> > If I have a single rabbit and NOT durable queue, all messages (also
>> >> > messages not yet ack'ed) in the queues are lost if the node goes
>> >> > down, that
>> >> > means that when the server restarts there are no messages left and so
>> >> > no
>> >> > retransmissions.
>> >> > With multiple rabbits, messages not yet ack'ed are mirrored in the
>> >> > other
>> >> > queues and in the event of failure of the master those messages will
>> >> > be
>> >> > retransmitted.
>> >> >
>> >> >
>> >> >>> Is there some plan to have a blueprint for this change?
>> >> >>I don't have such a plan. Should I?
>> >> >
>> >> > I need to deeply investigate and tests the HA Active/Active
>> >> > configuration, but If I can recreate some "complex" configuration to
>> >> > prove
>> >> > that we need to deal with the basic.cancel messages maybe it's worth
>> >> > to have
>> >> > one.
>> >> >
>> >> > Regards
>> >> > --
>> >> > Andrea Rosa
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> Eugene Kirpichov
>> >> http://www.linkedin.com/in/eugenekirpichov
>> >>
>> >> _______________________________________________
>> >> OpenStack-dev mailing list
>> >> OpenStack-dev at lists.openstack.org
>> >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>> >
>> >
>> >
>> >
>> > --
>> > Dan He
>> > -----------------------
>> >
>> >
>> >
>> > _______________________________________________
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>> > OpenStack-dev at lists.openstack.org
>> > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>> >
>>
>>
>>
>> --
>> Eugene Kirpichov
>> http://www.linkedin.com/in/eugenekirpichov
>>
>> _______________________________________________
>> OpenStack-dev mailing list
>> OpenStack-dev at lists.openstack.org
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>
>
>
>
> --
> Dan He
> -----------------------
>
>
>
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>



-- 
Eugene Kirpichov
http://www.linkedin.com/in/eugenekirpichov
We're hiring! http://tinyurl.com/mirantis-openstack-engineer