Re: pg_receivewal - couple of improvements

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Cc: Julien Rouhaud <rjuju123(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: pg_receivewal - couple of improvements
Date: 2022-02-07 02:53:41
Message-ID: YgCJtRFUAw4ke25m@paquier.xyz
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On Sun, Feb 06, 2022 at 01:01:41PM +0530, Bharath Rupireddy wrote:
> With the start position as an option, users can just provide the LSN
> from which they want to stream the WAL, in the above case, it can be
> from primary's latest checkpoint LSN.

This still strikes me as a dangerous thing to have, prone to errors
with a bunch of base backups wasted if one does a mistake as it would
be very easy to cause holes in the WAL stored, until one has to
redeploy from a base backup in urgency. This kind of control is
provided by replication slots for new locations, and the current
archive location if anything is stored, so I would leave it at that.

On top of that, this kind of control is prone to more race conditions
with the backend, as a concurrent checkpoint could make the LSN you
are looking for irrelevant.
--
Michael

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