Обсуждение: Initiate backup from routine?

Hello,

I would like to allow a co-worker to perform a backup of a database, such that the backup is saved to the database server itself. One use case is that (s)he would like an extra backup of a database, just before an application update is deployed. The co-worker doesn't have shell access on the DB server (so no sudo option), and we would like to allow this to happen without having to involve a DBA.

Is it possible to call pg_dump (or equivalent action) through a procedure/function?

--
Regards,
Troels Arvin

Is it possible to call pg_dump (or equivalent action) through a procedure/function?

  Are you able to install an untrusted language handler into the database?

Yes, if need be.

--
Regards,
Troels Arvin

On Wednesday, January 17, 2024, Troels Arvin <troels@arvin.dk> wrote:
> Is it possible to call pg_dump (or equivalent action) through a 
> procedure/function?

You could create a new schema and table that holds a flag column or a 
simple queue.
Then setup a script/app on a 5 minute cron that checks the status of the 
flag or queue to see if it needs to start a backup.
The script/app could update the table to show the user that the backup 
has started and when its finished.
The user account on the DB server that runs the code would have their 
shell set to /bin/false so they cannot login. The DB account used by the 
code would have the minimum privileges to perform the backup.

Or if it needs to be more real-time, the app could use LISTEN/NOTIFY to 
trigger the backup process. Then use cron on some interval to make sure 
the app is always running.

Then you just need the procedure to update the flag/queue or send a 
NOTIFY message.

Greetings,

* Ron Johnson (ronljohnsonjr@gmail.com) wrote:
> On Wed, Jan 17, 2024 at 9:41 AM Troels Arvin <troels@arvin.dk> wrote:
> > I would like to allow a co-worker to perform a backup of a database, such
> > that the backup is saved to the database server itself. One use case is
> > that (s)he would like an extra backup of a database, just before an
> > application update is deployed. The co-worker doesn't have shell access on
> > the DB server (so no sudo option), and we would like to allow this to
> > happen without having to involve a DBA.
> >
> > Is it possible to call pg_dump (or equivalent action) through a
> > procedure/function?
>
> An alternative is continuous (aka PITR) backups using something like
> PgBackRest.  Weekly full backups, incremental backups on the other six
> days, and WAL files that keep you up to date.

Strongly encourage this, of course.

> CHECKPOINT; and SELECT pg_switch_wal(); are all that's needed before she
> deploys the update.

Why force a checkpoint here?  It's not necessary and it's expensive.

I would suggest making use of pg_create_restore_point() so that you can
restore to exactly the point you want to.  Documentation for that is
here: https://www.postgresql.org/docs/current/functions-admin.html

Using pg_switch_wal() will make the WAL get pushed to the repo faster
than it would otherwise though that's not strictly necessary either
unless you're just outright killing the PG instance; a normal shutdown
should push that WAL out anyway.

Thanks,

Stephen