Horton

Re: Libpq support to connect to standby server as priority

Haribabu Kommi <kommi.haribabu@gmail.com>

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From: Haribabu Kommi <kommi.haribabu@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>, Laurenz Albe <laurenz.albe@cybertec.at>, Tom Lane <tgl@sss.pgh.pa.us>, Dave Cramer <pg@fastcrypt.com>, Jing Wang <jingwangian@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-03-21T20:32:43Z
Lists: pgsql-hackers 
On Fri, Mar 22, 2019 at 6:57 AM Robert Haas <robertmhaas@gmail.com> wrote:

> On Thu, Mar 21, 2019 at 2:26 AM Haribabu Kommi <kommi.haribabu@gmail.com>
> wrote:
> > Based on the above new options that can be added to target_session_attrs,
> >
> > primary - it is just an alias to the read-write option.
> > standby, prefer-standby - These options should check whether server is
> running in recovery mode or not
> > instead of checking whether server accepts read-only connections or not?
>
> I think it will be best to have one set of attributes that check
> default_transaction_read_only and a differently-named set that check
> pg_is_in_recovery().  For each, there should be one value that looks
> for a 'true' return and one value that looks for a 'false' return and
> perhaps values that accept either but prefer one or the other.
>
> IOW, there's no reason to make primary an alias for read-write.  If
> you want read-write, you can just say read-write.  But we can make
> 'primary' or 'master' look for a server that's not in recovery and
> 'standby' look for one that is.
>

OK, I agree with opinion. I will produce a patch for those new options.

Regards,
Haribabu Kommi
Fujitsu Australia

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.