Horton

Re: [Patch] pg_rewind: options to use restore_command from recovery.conf or command line

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Alexey Kondratov <a.kondratov@postgrespro.ru>, Andrey Borodin <x4mmm@yandex-team.ru>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, vladimirlesk@yandex-team.ru, Dmitriy Sarafannikov <dsarafan@yandex-team.ru>
Date: 2018-10-29T07:06:00Z
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. Move frontend-side archive APIs from src/common/ to src/fe_utils/

  2. Add -c/--restore-target-wal to pg_rewind

  3. Move routine definitions of xlogarchive.c to a new header file

  4. Move routine building restore_command to src/common/

  5. Integrate recovery.conf into postgresql.conf

On Mon, Oct 22, 2018 at 02:19:07PM -0300, Alvaro Herrera wrote:
> Hmm, I remember we had a project to have a new postmaster option that
> would report the value of some GUC option, so instead of parsing the
> file in the frontend, you'd invoke the backend to do the parsing.  But I
> don't know what became of that ... I don't see it in the postmaster
> --help output.

I did not recall this one.

> Of course, recovery.conf options are not GUCs either ... that's another
> pending patch.

But I do recall this one.  Still isn't it q bit different?  Because in
the case of pg_rewind let's remember that the origin cluster can be
offline or online, and that the target has to be offline.  I am also not
sure that we would want to use the same command restore_command with
pg_rewind and an instance in recovery.

Something that we could think about is directly to provide a command to
pg_rewind via command line.  Another possibility would be to have a
separate tool which scans a data folder and fetches by itself a range of
WAL segments wanted.  I have implemented something like that for an
internal solution, able to handle as well timeline jumps across
segments with a server-side and a client-side implementation (that was
to allow a passive to catch up using a set of WAL segments, if the
active does not have a replication slot, and segments were fetched
through a Postgres instance which has a local archive).
--
Michael