Horton

Re: Libpq support to connect to standby server as priority

Dave Cramer <pg@fastcrypt.com>

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From: Dave Cramer <pg@fastcrypt.com>
To: Haribabu Kommi <kommi.haribabu@gmail.com>
Cc: "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>, Laurenz Albe <laurenz.albe@cybertec.at>, Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, Jing Wang <jingwangian@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-02-28T12:32:22Z
Lists: pgsql-hackers 
> Now I will add the another parameter target_server_type to choose the
> primary, standby or prefer-standby
> as discussed in the upthreads with a new GUC variable.
>


So just to further confuse things here is a use case for "preferPrimary"

This is from the pgjdbc list.

"if the master instance fails, we would like the driver to communicate with
the secondary instance for read-only operations before the failover process
is commenced. The second use-case is when the master instance is
deliberately shut down for maintenance reasons and we do not want to fail
over to the secondary instance, but instead allow it to process user
queries throughout the maintenance."


see this for the thread.
https://www.postgresql.org/message-id/VI1PR05MB5295AE43EF9525EACC9E57ECBC750%40VI1PR05MB5295.eurprd05.prod.outlook.com

Dave Cramer

davec@postgresintl.com
www.postgresintl.com

Commits

  1. Make test_target_session_attrs more robust against connection failure.

  2. Extend the abilities of libpq's target_session_attrs parameter.

  3. Mark default_transaction_read_only as GUC_REPORT.

  4. Introduce a new GUC_REPORT setting "in_hot_standby".

  5. Avoid spamming the client with multiple ParameterStatus messages.

  6. Avoid harmless Valgrind no-buffer-pin errors.

  7. Restructure libpq code to remove some duplicity

  8. libpq: Add target_session_attrs parameter.