per https://doc.dovecot.org/configuration_manual/authentication/sql/, you can add more than one "host=" parameter in the "connect" directive, and leave dovecot to do round-robin load balancing. there will probably be a delay in processing while a failed database connection attempt times out.

or you can use a load balanced database footprint, using something like haproxy.  its not as simple as putting multiple databases behind haproxy and calling it done.  i use mariadb, which via galera, can do multi-primary HA, where all 3 primary instances can take write or read events.  you need to configure each mariadb instance with galara replication and then setup haproxy to properly attach to the databases and perform a service check.

postgresql or other databases may require different mechanisms to achieve fault tolerant HA.

On 8/30/22 4:18 AM, Sami Ketola wrote:

...

On 30. Aug 2022, at 5.13, Jack Snodgrass <jack@mylinuxguy.net> wrote:

I am using this file:

dovecot-sql.conf.ext

and in there  I have a

connect = "host=<dbserver> dbname=<dbname> user=<dbuser> password=<dbpass>"

My <dbserver> was down and I lost mail access for a few days before I realized that there was an issue.  How can I specify a backup server so that if my primary sql server goes down, a backup sql server will be queried?

Use haproxy.

Sami

presumably, you would have the same database parameters on different hosts, so only adding an additional "host=" parameter should suffice.  i would only add the additional parameters that are unique or different, and that should work.

connect = "host=<dbserver1> host=<dbserver2> dbname=<dbname> user=<dbuser> password=<dbpass>"

sorry to hear your going to test this in Prod. :(

On 8/30/22 6:10 PM, Jack Snodgrass wrote:

I prefer to use a 2 db approach where I specify 2 different Database servers as opposed to HAproxy.

I see on: https://doc.dovecot.org/configuration_manual/authentication/sql where it says:

*You can add multiple host parameters to the SQL connect string. Dovecot will do round robin load balancing between them. If one of them goes down, the others will handle the traffic.*

it would be really nice if that was expanded opon in the docs.... I am not sure WHO to ask that that be clarified.

I currently have:

connect = "host=<dbserver> dbname=<dbname> user=<dbuser> password=<dbpass>"

... would I use:

connect = "host=<dbserver> dbname=<dbname> user=<dbuser> password=<dbpass> host=<dbserver2> dbname=<dbname2> user=<dbuser2> password=<dbpass2>"

and the system would just see host/host, dbname/dbname user/user password/password and automatically map the correct dbname/user/password to the correct host or it is assumed that the 2nd host is the only thing that changes and the dbname/user/password are the same? or do I use:

connect = "host=<dbserver> dbname=<dbname> user=<dbuser> password=<dbpass> host2=<dbserver> dbname2=<dbname> user2=<dbuser> password2=<dbpass>"

to specify the host and host2 info?

"You can add multiple host parameters to the SQL connect string." is a bit lacking in info when you think about the possibility of having a different user/pass or dbname for the 2nd host instance.

I am going to play around with this on my production box... but having a bit more info in the docs would be preferred.

• jack

On 8/30/22 07:57 AM, Brendan Kearney wrote:

...

per https://doc.dovecot.org/configuration_manual/authentication/sql/, you can add more than one "host=" parameter in the "connect" directive, and leave dovecot to do round-robin load balancing.  there will probably be a delay in processing while a failed database connection attempt times out.

or you can use a load balanced database footprint, using something like haproxy.  its not as simple as putting multiple databases behind haproxy and calling it done.  i use mariadb, which via galera, can do multi-primary HA, where all 3 primary instances can take write or read events.  you need to configure each mariadb instance with galara replication and then setup haproxy to properly attach to the databases and perform a service check.

postgresql or other databases may require different mechanisms to achieve fault tolerant HA.

On 8/30/22 4:18 AM, Sami Ketola wrote:

...

...

On 30. Aug 2022, at 5.13, Jack Snodgrass <jack@mylinuxguy.net> wrote:

I am using this file:

dovecot-sql.conf.ext

and in there  I have a

connect = "host=<dbserver> dbname=<dbname> user=<dbuser> password=<dbpass>"

My <dbserver> was down and I lost mail access for a few days before I realized that there was an issue.  How can I specify a backup server so that if my primary sql server goes down, a backup sql server will be queried?

Use haproxy.

Sami

-- jack - Southlake Texas - mylinuxguy.net <http://url7179.mylinuxguy.net/ls/click?upn=qw3mUGlvypxOIEjnzoVznaPhh1QZR9rdwcvCQ0qavLA-3DUiiX_5qhfSnrBXIaXI7rIewPfzICYfubUoDIKRg6-2F2vb7-2BoHPlQu-2FfbGVKyxQX-2F2MK4nxxMgskp-2B7lkCgnLNSC-2BkHg-2BIZivmGnYzgw6K5Dw5Rkff8q-2FIoZHz2vWzOlfXpUNTznP1U4-2FAL3aStk0Rg0h6GpRg4at3NFRAD3w1S5-2B-2BXy4ne0c-2FXuQOKNksIOpgzzBd5FuBUlJpA0KfWocho2TNHnA-3D-3D>