On 10/07/2019 03:11 AM, Cyril Bonté wrote:
Le 06/10/2019 à 09:19, rihad a écrit :
Hi, all. This annoying bug can be experienced in 1.7-2.0 servers
(while 1.9 has added another bug of high CPU utilization - unrelated
to this). In essence, once an external server that we forward
internal requests to stops responding for some time and comes back to
life a bit later, more often than not haproxy can no longer reach it.
Without any other details (logs would be helpul), I tend to think
there's no bug here, but a configuration issue.
By default, haproxy resolves host names once, on start up. As you are
using a host name to delcare the smtp server, which oftenly updates
its IPs :
Configuration is very simple
server amazon email-smtp.us-west-2.amazonaws.com:587 check inter
30s fall 1440 rise 1
That's it. if email-smtp.us-west-2.amazonaws.com:587 fails
intermittently and the downtime lasts more than a few 30 sec checks,
it can then no longer be accessed via 127.0.0.2:2588 even if the
external servers resumes normal operation, and nothing short of a
reload (-sf) fixes the problem.
I guess that when it happens, email-smtp.us-west-2.amazonaws.com has a
new pool of IP addresses and haproxy can't connect to the old resolved
one. You should have a look to the documentation chapter "Server IP
address resolution using DNS" :
Thanks! But according to the manual, shouldn't haproxy re-resolve AWS
server name regardless of its resolver settings?
A few other events can trigger a name resolution at run time:
- when a server's health check ends up in a connection timeout: this may be
because the server has a new IP address. So we need to trigger a name
resolution to know this new IP.