Horton

Re: [Proposal] Adding Log File Capability to pg_createsubscriber

Gyan Sreejith <gyan.sreejith@gmail.com>

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From: Gyan Sreejith <gyan.sreejith@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Euler Taveira <euler@eulerto.com>, vignesh C <vignesh21@gmail.com>, "kuroda.hayato@fujitsu.com" <kuroda.hayato@fujitsu.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, Peter Smith <smithpb2250@gmail.com>
Date: 2025-12-23T23:22:11Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. pg_createsubscriber: Don't use MAXPGPATH

  2. pg_createsubscriber: Remove separate logfile_open() function

  3. pg_createsubscriber: Use logging.c log file callback

  4. Add log file support to logging.c

  5. pg_createsubscriber: Add -l/--logdir option to redirect output to files.

  6. pg_createsubscriber: Introduce module-specific logging functions.

Attachments

Thank you for the feedback everybody. As I read through this email chain, I
found differing opinions on how logging should be implemented. This
ambiguity leaves me unsure as to which solution(s) to pursue. As of right
now, I have attached the git-format patch like Hayato Kuroda recommended
(but it does not have any new changes). I am willing to implement whatever
solution when we reach a consensus.

Thank you for all of the help,
Gyan Sreejith

On Thu, Dec 18, 2025 at 1:49 AM Amit Kapila <amit.kapila16@gmail.com> wrote:

> On Thu, Dec 18, 2025 at 6:59 AM Euler Taveira <euler@eulerto.com> wrote:
> >
> > On Wed, Dec 17, 2025, at 7:07 AM, vignesh C wrote:
> > >
> > > By providing this as an option, users can store the log files outside
> > > the data directory, eliminating the need for any additional handling
> > > during backups.
> > >
> >
> > Do we really need an option to capture the stdout / stderr output to a
> file? I
> > doubt it. There is already various ways to capture. psql and pg_upgrade
> are the
> > only tools that have this option.
> >
>
> pg_ctl also has the -l option. I think any place where long
> text/errors can be outputted, a log file is preferred because one
> could later parse it to know the exact details. Also, splitting the
> log as proposed here or in pg_upgrade helps to navigate the LOG like
> is the problem in start/stop of the server or a pub-sub setup?
> Similarly the log can be splitted for pub/sub specific information.
> There appears to be some useful information like:
>
> pg_createsubscriber: warning: two_phase option will not be enabled for
> replication slots
> pg_createsubscriber: detail: Subscriptions will be created with the
> two_phase option disabled. Prepared transactions will be replicated at
> COMMIT PREPARED.
> pg_createsubscriber: hint: You can use the command-line option
> --enable-two-phase to enable two_phase.
>
> I think it will be useful to LOG this separately from the main LOG [1]
> (which can contain server specific info as follows) so that users can
> consider running pg_createsubscriber with additional options or
> changing the subscriber configuration once setup is complete.
>
> [1]:
> [startup] LOG:  database system was interrupted; last known up at
> 2025-12-17 14:46:07 IST
> [startup] LOG:  starting backup recovery with redo LSN 0/06000028,
> checkpoint LSN 0/06000080, on timeline ID 1
> [startup] LOG:  entering standby mode
> [startup] LOG:  redo starts at 0/06000028
> [startup] LOG:  completed backup recovery with redo LSN 0/06000028 and
> end LSN 0/06000120
> [startup] LOG:  consistent recovery state reached at 0/06000120
>
> --
> With Regards,
> Amit Kapila.
>