dovecot director and keepalived

[Eirik Rye]

On 03/15/2021 8:43 PM, Paterakis E. Ioannis wrote:
> It's not keepalived's work to tell the directors which backend is 
> up/down. You can use poolmon for that. keepalived will make sure the 
> floating ip will always be assigned on an alive haproxy. Then it's 
> haproxies' work to check the aliveness of directors. Then It's Directors 
> job to assign the users to the same dovecot backend all the time, and so 
> on....

What is the purpose of HAProxy in this director setup? It seems like an 
unecessary extra layer of proxying in your example.

We run a setup with keepalived directors, and a bunch of dovecot IMAP 
servers, and this works well.

The directors have two IPs each, one static and one floating 
(keepalived). The IPs listed in the "director_servers" setting are the 
static IPs. The floating IPs are listed in DNS.

If you simply configure dovecot to bind to all interfaces, and instead 
use iptables to limit IMAP/POP/director connections to the interfaces 
you want, there is no need to set `net.ipv4.ip_nonlocal_bind=1`.

With all that said, I do agree that there should be a way to explicitly 
set the director's announce/listen address, instead of using the 
net_try_bind() method.

If you need this feature, I doubt it would be very hard to patch by 
adding a new configuration option, and then modifying this code to check 
said option value, and use it (if present) instead of trying to 
determine the IP:

https://github.com/dovecot/core/blob/fb6aa64435e0ffd66b81cd4895127187f28fa20b/src/director/director.c#L86

- Eirik