Re: [Sqlgrey-users] Load balancing question, part 2

[Gary S. <gar...@ho...>]

> Ive not tried LVS'ing sqlgrey but i do use LVS (ipvsadm) alot.
> I run sqlgrey on the MTA, and then LVS to the MTA's. The MTA's then
> communicate with sqlgrey on localhost. Sqlgrey reads from MySQL on
> localhost and writes to a master for replication.
> 
> 
> When you say ESTABLISHED, i assume you mean from looking at the output
> from netstat or something like it. If so, i cant imagine that it can be
> an application level problem. If postfix deliberately closes the
> connection (eg due to a timeout), it should/would transmit either a TCP
> RST or FIN. The receiving party (your cluster node) will handle RST and
> FIN in the kernel's ip-stack, not in the application.
> Upon receiving FIN, "ESTABLISHED" should have changed to "CLOSE-WAIT" in
> netstat.
> Which suggests that your cluster node does not actually receive a FIN.
> Which again suggest that the connection drop before your cluster node,
> ie. the loadbalancer.
> 
> Of course, not knowing you LVS setup and config, i can only guess. But a
> typical misconfigure would be using "Direct Routing" (the "gatewaying"
> option in ipvsadm. which is default), without taking precautions against
> the cluster nodes ARP'ing the virutal ip. If this is the case, all
> cluster nodes would "battle" for the virtual ip, making the ip "hop"
> around the nodes.
> That would, i imagine, leave ESTABLISHED connections behind.

Dan, 

I'll look into this.  The arp problem makes sense.  We have been doing some work with the arp configurations on these.  This is a new cluster environment.  As for the routing, we are currently using NAT (-m) for all nodes.

I'm pretty sure that's it's the load balancer that has introduced the problems.  We do have other IVPS nodes running (which have been running for years) and this is the first set that I have run into the lingering connection problems.

Thanks for the pointers.  
 
> Regards
> - Dan Faerch
> 
> 
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