multiple / backup sql servers for sql server access

[Brendan Kearney]

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 at 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
>
>
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