Horton

RE: Libpq support to connect to standby server as priority

Tsunakawa, Takayuki <tsunakawa.takay@jp.fujitsu.com>

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From: "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>
To: 'Haribabu Kommi' <kommi.haribabu@gmail.com>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>, Tom Lane <tgl@sss.pgh.pa.us>, Dave Cramer <pg@fastcrypt.com>, Robert Haas <robertmhaas@gmail.com>, "Jing Wang" <jingwangian@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-01-21T06:48:14Z
Lists: pgsql-hackers 
From: Haribabu Kommi [mailto:kommi.haribabu@gmail.com]
> Thanks for finding out the problem, how about the following way of checking
> for prefer-read/prefer-standby.
> 
> 1. (default_transaction_read_only = true and recovery = true)
> 
> 2. If none of the host satisfies the above scenario, then recovery = true
> 3. Last check is for default_transaction_read_only = true

That would be fine.  But as I mentioned in another mail, I think "get read-only session" and "connect to standby" differ.  So I find it better to separate parameters for those request; target_session_attr and target_server_type.


Regards
Takayuki Tsunakawa

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.