Re: Patch: Implement failover on libpq connect level.

On Tue, Nov 15, 2016 at 11:31 PM, Mithun Cy <mithun.cy@enterprisedb.com> wrote:
>> > So I am tempted to just
>> > hold my nose and hard-code the SQL as JDBC is presumably already
>> doing.
>
> JDBC is sending "show transaction_read_only" to find whether it is master or
> not.
> Victor's patch also started with it, but later it was transformed into
> pg_is_in_recovery
> by him as it appeared more appropriate to identify the master / slave.

Hmm, let's go back to the JDBC method, then.  "show
transaction_read_only" will return true on a standby, but presumably
also on any other non-writable node.  You could even force it to be
true artificially if you wanted to force traffic off of a node, using
ALTER {SYSTEM|USER ...|DATABASE ..} SET default_transaction_read_only
= on

I think that would address Alvaro's concern, and it's nicer anyway if
libpq and JDBC are doing the same thing.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company