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From: Koen De Groote <[email protected]>
To: Adrian Klaver <[email protected]>
Cc: PostgreSQL General <[email protected]>
Subject: Re: Postgres restore sometimes restores to a point 2 days in the past
Date: Fri, 31 Jan 2025 22:52:39 +0100
Message-ID: <CAGbX52H5r2ObhTszzX5L+wKL9XYWvEeCT4xfvU+D6zgvOrPHTg@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAGbX52HkW6926c4tY781+iH01x_0qw6Sfo=kT+LHjo_mENqOfQ@mail.gmail.com>
	<[email protected]>
	<CAGbX52E5_7fPZVW0YSjoTmj5qN-aORXpPqFF+bKCiicM+h3EZQ@mail.gmail.com>
	<[email protected]>

> I should have asked earlier what is the archive command

The example from the documentation, but with GZIP. So from the
documentation:
https://www.postgresql.org/docs/16/continuous-archiving.html#BACKUP-ARCHIVING-WAL

Which becomes this: archive_command = 'test ! -f
/mnt/server/archivedir/%f.gz && gzip -c %p /mnt/server/archivedir/%f.gz'


> Are you setting standby.signal or recovery.signal or both

Sorry, I keep confusing them. I checked my deployment code, it's
recovery.signal and only that.

Regards,
Koen De Groote


On Fri, Jan 31, 2025 at 10:26 PM Adrian Klaver <[email protected]>
wrote:

> On 1/31/25 12:10, Koen De Groote wrote:
> >  > What is the complete pg_basebackup command?
>
> > 2/ All my WAL files are archived and uploaded to the cloud. So, I can
> > just have them downloaded.
>
> I should have asked earlier what is the archive command?
>
> Are
> >  > What is determining that a particular WAL file should be asked for?
> >
> > The postgres server itself does this. Here's the documentation:
> >
> https://www.postgresql.org/docs/16/runtime-config-wal.html#GUC-RESTORE-COMMAND
> <
> https://www.postgresql.org/docs/16/runtime-config-wal.html#GUC-RESTORE-COMMAND
> >
> >
> > And here: https://www.postgresql.org/docs/current/warm-standby.html
> > <https://www.postgresql.org/docs/current/warm-standby.html;
> >
> > In practice, Postgres will see the "standby.signal" file and start
>
> In your OP you say:
>
> "It downloads the basebackup, unpacks it, sets a recovery.signal, ..."
>
> Are you setting standby.signal or recovery.signal or both?
>
>
> > asking for WAL files. It will read the database it has and determine
> > what the next WAL filename should be. And then it asks for it. And it
> > will keep asking for these hexadecimal filenames, 1 at a time, for as
> > long as the command or set of commands provided to "restore_command"
> > returns exit code 0. If the process receives any other exit code, it
> > stops recovery, switches timeline, and considers the database to be up
> > and running at the state its in.
> >
> > It's constantly asking "I want this file now" and the script I have as
> > the restore command will attempt to download it from the cloud. Then it
> > will attempt to unzip it and move it into place. If any of these steps
> > fails, I return exit code 1.
> >
>
> > Regards,
> > Koen De Groote
> >
> >
>
>
> --
> Adrian Klaver
> [email protected]
>
>

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