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.r...@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 _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : openstack@lists.launchpad.net Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
