Re: [exim] ratelimit-ACL across multiple hosts

On Tue, Aug 28, 2007 at 06:08:30AM -0700, Marc Perkel wrote:
> Mark de Vries wrote:
> > On Mon, 27 Aug 2007, exim-users-ml@??? wrote:
> >> we have several servers which handle incoming smtp-connections as a
> >> loadbalancing-setup, which also make use of the ratelimit-database.
> >>
> >> one main disadvantage is, that you had to multiply the rate by the
> >> number of hosts in the setup.
> >>
> >> is it possible to share the ratelimit-hints-database across several
> >> hosts - e.g. by NFS? are there some pitfalls, especially when the
> >> nodes are on high load/traffic?
> >
> > I have wondered about this myself. Althoug I would be more interrested in
> > sharing the callout cache between several servers....
> >
> > If anyone tried and would like to share there findings that would be
> > great.
>
> I'd love to have it too - but I had assumed that it wasn't possible. In
> my case in particular because I have hosts in multiple locations and if
> the central host fails the other hosts would need to switch to
> independent rate limiting. But I'd love it if it magicall worked.

If you are using a hardware or software load balancer, check to see if
your balancer has the ability to do IP-persistent load balancing.
That would allow you to ensure that all IP addresses (perhaps within a
specific time frame) would always go to the same server.

It's not ideal, but if you tend to only care about short-term
ratelimits (such as how many messages per hour, etc), then this works
wonderfully and is how we eventually dealt with the issue.

SQL storage for rate-limits isn't ideal without some sort of intervening
proxy daemon given the (re)connection load on the SQL server on high
traffic mail servers.

--
Dean Brooks
dean@???