Re: Patch: Implement failover on libpq connect level.

From: pgsql-hackers-owner(at)postgresql(dot)org
> [mailto:pgsql-hackers-owner(at)postgresql(dot)org] On Behalf Of Mithun Cy
> Among the remaining things I have worked on failover to new master idea.
> Below patch implement that idea. This is taken from Victors patch but
> rewritten by me to do some cleanup. As in Victor's patch we have a new
> connection parameter "target_server_type", It can take 2 values 1. "any"
> 2. "master" with DEFAULT as "any". If it's has the value "any" we can connect
> to any of the host server (both master(primary) and slave(standby)). If
> the value is "master" then we try to connect to master(primary) only.
> NOTE: Parameter name is inspired and taken from PostgreSql JDBC Driver
> <https://jdbc.postgresql.org/documentation/head/connect.html> .

I'm interested to review this patch (but I haven't read it yet, I'm reading Robert's patch now.) Are you planning a new CommitFest entry?

Why don't you add "standby" and "prefer_standby" as the target_server_type value? Are you thinking that those values are useful with load balancing feature?

> The main difference between Victor's and this new patch is Default value
> of parameter target_server_type. In Victor's patch if number of host in
> connection string is 1 then default value is "any" (This was done to make
> sure old psql connect to standby as it is now). If it is greater than 1
> then default value is set as "master". For me this appeared slightly
> inconsistent having default value as "any" for any number of connection
> appeared more appropriate which is also backward compatible. And, if user
> want failover to master he should ask for it by setting
> target_server_type=master in connection string.

That's sensible, I agree.

Regards
Takayuki Tsunakawa