Re: Missing pg_control crashes postmaster - Mailing list pgsql-hackers

From Andres Freund
Subject Re: Missing pg_control crashes postmaster
Date
Msg-id 2A3449E6-D4C9-4A81-BBDB-47E92037EC7A@anarazel.de
Whole thread Raw
In response to Missing pg_control crashes postmaster  (Brian Faherty <anothergenericuser@gmail.com>)
List pgsql-hackers

On July 23, 2018 12:31:13 PM PDT, Brian Faherty <anothergenericuser@gmail.com> wrote:
>Hey Hackers,
>
>If a postmaster is running and the pg_control file is removed postgres
>will PANIC.
>
>Steps to recreate:
>
>1.) start a new cluster
>2.) rm $DATADIR/pg_control
>3.) psql => CHECKPOINT;
>
>PANIC:  could not open control file "global/pg_control": No such file
>or directory
>
>After the PANIC there is no pg_control. Recovery would be difficult
>without a replica or a backup. Instead of crashing we can just write a
>new pg_control file since all the data is in memory at the time.
>
>There does not really seem to be a need for this behavior as all the
>information postgres needs is in memory at this point. I propose with
>a patch to just recreate pg_control on updates if it does not exist.

What's the issue this would solve? Given that there's moments, until the control file is rewritten, where you would be
toasteither way, I don't buy this gives much added safety. Nor have you explained which realistic scenarios lead to the
filemissing, without much broader problems being present. 


Andres
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.


pgsql-hackers by date:

Previous
From: "David G. Johnston"
Date:
Subject: Re: Missing pg_control crashes postmaster
Next
From: Jeff Janes
Date:
Subject: Re: BUG #15182: Canceling authentication due to timeout aka Denial ofService Attack