Subject: Pg jdbc DNS failover

From: Nikolay Prokofiev <[email-masked]>
Date: Tue, 21 Nov 2023 12:07:30 +0300

Hi. According to pgjdbc documantation
<https://jdbc.postgresql.org/documentation/use/#connection-fail-over>, the
driver supports failover when ip addresses and ports of host are comma
separated, like this:
jdbc:postgresql://my-db-host-slave-1:5432,my-db-host-master-1:5432/database?targetServerType=primary
.

But it's not convenient, because we use k8s for pg, and there may be more
slaves added and master ip may be changed.

I want to store all my hosts in DNS and to specify one hostname like this:
jdbc:postgresql://my-db-host.local:5432/database?targetServerType=primary

I have a dns record with 2 ip addresses:

$ nslookup my-db-host.local
Server: 192.168.1.1
Address: 192.168.1.1#53

Non-authoritative answer:
Name: my-db-host-slave-1
Address: 192.168.10.21
Name: my-db-host-master-1
Address: 192.168.11.25

and I tried to specify it like this:
jdbc:postgresql://my-db-host.local:5432/database?targetServerType=primary.

But this way it only picks the first ip - slave and fails with
org.postgresql.util.PSQLException:
Could not find a server with specified targetServerType: primary

Is there any workaround for using dns failover? May be some options in
connection pools if driver does not support that?

---

From: Dave Cramer <[email-masked]>
Date: Tue, 21 Nov 2023 08:07:46 -0500

On Tue, 21 Nov 2023 at 04:07, Nikolay Prokofiev <[email-masked]>
wrote:

> <https://jdbc.postgresql.org/documentation/use/#connection-fail-over>,
> the driver supports failover when ip addresses and ports of host are comma
> separated, like this:
> But this way it only picks the first ip - slave and fails with org.postgresql.util.PSQLException:

Currently no.  It would be a useful addition however.

Dave