public inbox for [email protected]  

help / color / mirror / Atom feed

From: David Steele <[email protected]>
To: Robert Haas <[email protected]>
Cc: Pg Hackers <[email protected]>
Subject: Re: pg_combinebackup does not detect missing files
Date: Thu, 18 Apr 2024 09:09:37 +1000
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+TgmoZmuhkjGx=97kEniMRNC9Qaifjh0zMFZnHne72JGFNdKA@mail.gmail.com>
References: <[email protected]>
	<CA+TgmoaVxr_o3mrDBrBcXm3gowr9Qc4ABW-c73NR_201KkDavw@mail.gmail.com>
	<[email protected]>
	<CA+TgmoZmuhkjGx=97kEniMRNC9Qaifjh0zMFZnHne72JGFNdKA@mail.gmail.com>

On 4/18/24 01:03, Robert Haas wrote:
> On Tue, Apr 16, 2024 at 7:25 PM David Steele <[email protected]> wrote:
> 
> But it will not go out of its way to perform checks that are unrelated
> to its documented purpose. And I don't think it should, especially if
> we have another tool that already does that.
> 
>>> I'm not averse to having some kind of statement in the documentation
>>> along the lines of "Note that pg_combinebackup does not attempt to
>>> verify that the individual backups are intact; for that, use
>>> pg_verifybackup."
>>
>> I think we should do this at a minimum.
> 
> Here is a patch to do that.

I think here:

+   <application>pg_basebackup</application> only attempts to verify

you mean:

+   <application>pg_combinebackup</application> only attempts to verify

Otherwise this looks good to me.

>> Especially given how pg_combinebackup works, backups are going to
>> undergo a lot of user manipulation (pushing to and pull from storage,
>> decompressing, untaring, etc.) and I think that means we should take
>> extra care.
> 
> We are in agreement on that point, if nothing else. I am terrified of
> users having problems with pg_combinebackup and me not being able to
> tell whether those problems are due to user error, Robert error, or
> something else. I put a lot of effort into detecting dumb things that
> I thought a user might do, and a lot of effort into debugging output
> so that when things do go wrong anyway, we have a reasonable chance of
> figuring out exactly where they went wrong. We do seem to have a
> philosophical difference about what the scope of those checks ought to
> be, and I don't really expect what I wrote above to convince you that
> my position is correct, but perhaps it will convince you that I have a
> thoughtful position, as opposed to just having done stuff at random.

Fair enough. I accept that your reasoning is not random, but I'm still 
not very satisfied that the user needs to run a separate and rather 
expensive process to do the verification when pg_combinebackup already 
has the necessary information at hand. My guess is that most users will 
elect to skip verification.

At least now they'll have the information they need to make an informed 
choice.

Regards,
-David

view thread (5+ messages)

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected]
  Subject: Re: pg_combinebackup does not detect missing files
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox