[ClusterLabs] mail server (postfix)

[Vladislav Bogdanov]

05.06.2016 22:22, Dimitri Maziuk wrote:
> On 06/04/2016 01:02 PM, Vladislav Bogdanov wrote:
>
>> I'd modify RA to support master/slave concept.
>
> I'm assuming you use a shared mail store on your imapd cluster? I want

No, I use cyrus internal replication.

> to host the storage on the same cluster with mail daemons. I want to a)
> stop accepting mail, b) fail-over drbd maildirs, then c) restart postfix
> in send-only "slave" configuration. On the other node I could simply
> restart the "master" postfix after b), but on the node going passive the
> b) has to be between a) and c).

Do you have reasons for b) to be strictly between a) and c) ?

I'd propose something as the following:
0a) service is a master on one node (nodeA) - it listens on socket and 
stores mail to DRBD-backd maildirs.
0b) service is a slave on second node (nodeB) - send-only config
1) stop VIP on nodeA
2) demote service on nodeA (replace config and restart/reload it 
internally in the RA) - that would combine your a) and c)
3) demote DRBD on nodeA (first part of your b) )
4) promote DRBD on nodeB (second part of b) )
5) promote service on nodeB - replace config and internally reload/restart
6) start VIP on nodeB

1-2 and 5-6 pairs may need to be reversed if you bind service to a 
specific VIP (instead of listening on INADDR_ANY).

For 2 and 5 to work correctly you need to colocate service in *master* 
role with DRBD in *master* role. That way "slave" service instance does 
not require DRBD at all.

Hope this helps,
Vladislav