Re: Patch: Implement failover on libpq connect level.

On Mon, Nov 14, 2016 at 11:31 AM, Tsunakawa, Takayuki <
tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:
> PGconn->target_server_type is not freed in freePGconn().

Thanks, will fix in new patch.

>Could you add PGTARGETSERVERTYPE environment variable? Like other
variables, it will ease testing, since users can change the behavior
>without altering the connection string here and there.

Okay, will add one.

> I think it would be better to expose the server state via ParameterStatus
protocol message like standard_conforming_strings, instead of running >
>"SELECT pg_is_in_recovery()". We shouldn't want to add one round trip to
check the server type (master, standby). postmaster can return the server
>type based on its state (pmState); PM_RUN is master, and PM_HOT_STANDBY is
standby. In addition, as an impractical concern, DBA can revoke >EXECUTE
privilege on pg_is_in_recovery() from non-superusers.

If you are suggesting me to change in protocol messages, I think that would
not be backward compatible to older version servers. I also think such
level of protocol changes will not be allowed. with connection status
CONNECTION_SETENV used for protocol version 2.0 setup, we sent some query
like
"select pg_catalog.pg_client_encoding()" for same. So I think using "SELECT
pg_is_in_recovery()" should be fine.
-
Thanks and Regards
Mithun C Y
EnterpriseDB: http://www.enterprisedb.com