Hi Michael,
On Fri, Apr 17, 2009 at 04:47:38PM +0100, Michael Miller wrote:
Hi,
I am doing some intial testing with HAProxy and have come across a
problem I don't seem to be able to resolve.
A summary of what I am initially trying to achieve follows. I am trying
to use HAProxy to provide a VIP that passes on a tcp (SMTP as it
happens) stream to a backend server. If that server is down, I would
like the connection forwarded to a backup server.
Doing some testing and watching the status page reveals that if both
servers are configured as normal, rather than backup, servers the tcp
connection is rerouted when the initial attempt to connect fails.
However, when one server is configured as backup, the connection never
gets to the backup server.
The config I am using is:
global
log 127.0.0.1 local0
log 127.0.0.1 local1 notice
maxconn 4096
pidfile /var/run/haproxy.pid
##chroot /usr/share/haproxy
user haproxy
group haproxy
daemon
#debug
#quiet
spread-checks 10
defaults default_settings
log global
modehttp
option httplog
option dontlognull
option abortonclose
## option allbackups
option clitcpka
option srvtcpka
option forwardfor
retries 10
option redispatch
maxconn 2000
backlog 256
timeout connect 5000
timeout client 5
timeout server 1
listen www-health
bind 0.0.0.0:8080
mode http
monitor-uri /haproxy
stats enable
stats uri /stats
listen smtp
log global
bind 0.0.0.0:25
mode tcp
#option smtpchk HELO haproxy.local
option tcplog
balance roundrobin
rate-limit sessions 10
timeout connect 1
timeout client 6
timeout server 6
server smtp01 10.1.1.5:25
server smtp02 10.1.1.6:25 backup
Note that I am trying to avoid using active health checks and am hoping
that the tcp connection failure when connecting to the primary will fall
back to the backup server. This works as expected when both servers are
configured as active rather than backup servers. Looking at the
status page when one is down, the 10 retries against the down server
are shown and then the tcp connection succeeds to the second server.
Is this a bug that the tcp connection is not forwarded to the backup
server, or am I missing some obvious configuration settings?
Neither :-)
It is designed to work like this though I agree that it is not
necessarily obvious. As documented, a backup server is only activated
when all other servers are down. Here, since you are not checking the
active server, it is never down. That's as simple as that. May I ask
why you don't want to enable health-checks ? That's a rather strange
choice, as it means you don't care about the server's status but
still hope that a failure will be detected fast enough to hope a
redispatch would work. You might destroy a lot of traffic acting
like this.
Also, there is an smtpchk option which is able to check that your
server responds on port 25. You should really use it. You don't
necessarily need to check every second, for SMTP generally, checking
once a minute may be enough for small setups.
Regards,
Willy
