Re: Dealing with a server going down

Wow.. I don't know how I missed that in the docs. I think I must've gotten mixed up between that kind of health checking and the health-checking "mode". I gave that a try and it worked perfectly. Thanks Willy for the response and the great product!

-Martin

On 11/19/07, Willy Tarreau <w#1wt.eu> wrote:
>
> On Sun, Nov 18, 2007 at 11:33:22PM -0500, Martin Goldman wrote:
> > Hi folks,
> >
> > I'm new to haproxy, and I'm working on a simple SMTP cluster with 2
> servers
> > to learn how it works. I've got a quick question:
> >
> > When both SMTP servers are up and running, when I telnet to the cluster
> on
> > port 25, I'm immediately connected and receive the SMTP server's
> greeting
> > banner, sometimes indicating I'm connected to one server and sometimes
> to
> > the other (demonstrating that load balancing is working). If I stop the
> SMTP
> > service on one server and retry my connection to the cluster, I still
> get
> > immediately connected and receive the SMTP greeting banner, now always
> > indicating that I'm connected to the other server. But if I take one
> server
> > off the network entirely and connect to the cluster once again, there's
> very
> > often a delay before the SMTP greeting banner appears (the duration of
> which
> > depends upon the value of contimeout). I suppose this means that haproxy
> is
> > trying to send some of my requests to the server that's down, then it's
> > waiting for the connections to time out before trying the other server.
> >
> > Now, I could be wrong, but it seems to me that this arrangement doesn't
> > provide the highest quality of service when one of the nodes in your
> cluster
> > goes down -- although all requests are completed eventually, some are
> sent
> > to the bad node and have to time out before they can be serviced by
> another
> > node. It seems like it should be possible to determine when a node goes
> > down, and to have haproxy stop sending requests to that node until it
> comes
> > back up.
> >
> > So I guess my question is: is there a way to do this? Or am I completely
>
> > misunderstanding something?
>
> I think that you have not enabled health checks on your servers. You
> should
> use the "check inter XXX" arguments on each server line. Also, keep in
> mind
> that there is an "smtpchk" option to perform SMTP checks instead of pure
> TCP
> checks.
>
> Regards,
> Willy
>
>
Received on 2007/11/19 13:57