Re: HAproxy SMTP check

From: David Rorex <>
Date: Thu, 8 Jan 2009 14:14:52 -0800

It should be possible, I believe there's an option to have health checks go to a different port than the main connections go to. Then you'd just need a daemon on that same machine, listening on a different port, which can check the server's status and return a success or failure.

On Thu, Jan 8, 2009 at 2:01 PM, Eric Schwab <> wrote:

> We are using haproxy to load balance inbound SMTP traffic across several
> servers. At present the load-balancing is done via the 'leastconn'
> algorithm within haproxy.
> We are trying to add some intelligence to give us control over how inbound
> SMTP traffic is routed in the event that one or more of those SMTP servers
> are in a sub-optimal state, and that state cannot be determined from a
> simple connection (or lack thereof) to port 25.
> (As a simple example, one of the servers may have a very high queue, which
> would not impact its ability to receive new messages via port 25, but we
> would want to reduce traffic to that particular server.) Without going into
> too much more detail, the load-balancing algorithms within haproxy will not
> have sufficient information to reroute traffic the way we would like to.
> The ideal scenario for us would be for haproxy to issue an HTTP check (even
> though the incoming connections are for an smtp service) to a destination
> server in the pool, and upon receiving a 4xx or 5xx level response, haproxy
> would pull that server out of the pool, thus not allowing new SMTP
> connections -- however not terminating existing connections.
> Is this possible?
> --
> Eric Schwab
> Internet Integration, Inc.
> Tel: 310-571-3200
> Fax: 310-571-3434
Received on 2009/01/08 23:14

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