The mailing list for listmasters using Sympa

[Steve Shipway <address@concealed>]

> I'm still struggling to find an SMTP through other channels.  But for this 
> group,
> I wonder if anybody has a good approach in clustering Sympa for failover?

We've decided on using VMware site recovery manager and replicated SAN 
volumes, as this is the easiest solution for us (we already use it for many 
other systems).

Given that Sympa does not need a very fast mean time to recovery -- email 
just 
queues up and can be delivered later -- we can live with a slower DR rather 
than HA.

However, if you need HA, here's a way to do it, though it is ugly.

First, set up a replicated MySQL cluster for the database.  You may not be 
able to use an NDB backend, since it limits certain SQL commands, foreign 
keys 
and so on.  We've not tested the Sympa database against the NDB limitations, 
but if it is compatible, then an NDB cluster would work.  Multiple frontends 
and backends, and hide multiple frontends behind a failover load balancer. 
So, now you have an HA database.

Then you can set up two identical Sympa systems, which will be in 
active/passive mode.  If you have an HA fileserver, you could set the list 
archive and the list_data path on a shared NFS filesystem; else you can set 
up 
a periodic copy from prod to standby, but then you'd lose archives written 
while in failover, and you would probably have to make the configuration 
read-only while in failover.

The two web interfaces (if you're running a web interface on the standby 
server) can sit behind a load balancer in active/standby.

The SMTP should be set up the either MX records giving the primary higher 
priority, or else with port 25 behind a load balancer in active/standby  so 
that mails only go to the second in a failover situation.  If you have the 
archive on a shared filesystem, or do not use archives, then you could have 
them running active/active.

I think this should work, but we have not tested it.  In particular, there 
might be locking issues between separate servers handling the same 
distribution table in the database.  If this is a problem, you could always 
make failover manual, and just start up your standby Sympa (and associated 
postfix and httpd) when necessary.  Unless you have a big need for the web 
interface to be HA this should be enough for email distribution?

Steve

Steve Shipway
address@concealed

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