On 14/3/2021 6:52 μ.μ., Steven Varco wrote:
Hi All
I’m trying to establish a dovecot HA setup with two loadbalancers, running
keepalived for sharing a virtual public IP.
On the same machines I’m running a dovecot director which proxies the requests
to two underlying mail servers (on seperate machines).
Now I’m hitting the issue with the way director determines his „Self IP“ by
trying to bind to all configured director_servers IPs, taking the first one
possible.
Each Director has to listen only on the static IP address of each
machine. Then you have to configure the 2 directors in the HAproxies.
The floating ip with keepalived will work along with the 2 HAproxies.
However this approach only works, when the sysctl setting is:
net.ipv4.ip_nonlocal_bind=0
On the other side keepalived needs net.ipv4.ip_nonlocal_bind=1 in order to bind
the VIP.
You don't have to mess with these settings.
Other possible solutions I could think about:
- Configure each director as „independent“ by setting only one IP in
director_servers.
=> With this aporach you would loose the user to mailserver mapping,
although only in a a case of a failover on the loadbalancer, which might can be
neglected (or are there any other fallbacks?)
The two directors have a connection to each other, so both know at the
same time where's a user mapped. You don't have to worry about that. The
user->dovecot mapping will work without any problems even if there is a
failover.
- Putting director on seperated intermediate machines and proxing the requests through
haproxy on the keepalived servers (keepalived -> haproxy -> director -> IMAP
=> Besides the disadvantage of having another bunch of servers in the
chain, also some special configuration on the directory servers might be
neccessary to assure director works neatly with haproxy.
The identical scenario will be to have keepalived along with haproxy on
same machine, and directors on another. But can work with all three on
the same as well. I use the keepalived, haproxy on two machines, with 2
directors underneath each one on different machine/hardware for the high
availability's sake, and below them there are 3 dovecot servers.
So 2021, what is the „correct“ (best practive) way of having a reduntant HA
setup for dovecot?
Cheers :-)
John
