On Mon, Jul 09, 2001 at 05:35:27PM -0400,
Ross West <exim@???> is thought to have said:
> Hi there,
>
> I was wondering if there is a way to get exim under high incoming
> tcp connection load to just refuse the connection instead of answering the
> tcp connections and issuing a "421 too many connections" message.
>
> The reason is we are running a L4 load balancer in front of the
> servers, and it will automatically re-route the incoming session if
> the server doesn't answer the connection - the LB proxies the inbound
> initial TCP setup and re-routes it if necessary. A very nice thing if
> the server dies for some reason.
>
> I've been reading/playing around with the "smtp_accept_max" [and
> associated] parameters but to no avail, maybe I'm just not hitting the
> right combination yet.
>
> I'd hate to just set smtp_accept_max and let the L4 system just go by
> system load with no runaway catches. :-)
Hmm. Well in my case at least, I run 3 servers behind an Alteon 180 and
set it to load balance the number of connections based on round-robin. So
in practice the number of TCP connections to my mail servers is nearly
equal at any given time. I'd think that if you'd see a "too many
connections" message on one, you should see it on all of them if the load
balancer is in fact distributing evenly.
Also while this doesn't answer your question, I'm fairly certain that most
L4 load balancers are smart enough these days to poll the real ips and
look at the response. So you might be able to mark a server as unavailable
if it's throwing a 4xx in the banner.
Tabor
--
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Tabor J. Wells twells@???
Fsck It! Just another victim of the ambient morality
