Horton

Re: BUG #17928: Standby fails to decode WAL on termination of primary

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Noah Misch <noah@leadboat.com>, Tom Lane <tgl@sss.pgh.pa.us>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
Date: 2023-08-15T03:00:30Z
Lists: pgsql-bugs

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Correct assertion and comments about XLogRecordMaxSize.

  2. Fix edge-case for xl_tot_len broken by bae868ca.

  3. Don't use Perl pack('Q') in 039_end_of_wal.pl.

  4. Don't trust unvalidated xl_tot_len.

  5. Make recovery report error message when invalid page header is found.

  6. Add more protections in WAL record APIs against overflows

On Tue, Aug 15, 2023 at 02:36:10PM +1200, Thomas Munro wrote:
> Yeah, I think that sounds quite promising, and funnily enough I was
> just now working on some Perl code that appends controlled junk to the
> WAL in a test like that so we can try to hit all the error paths...

I am pretty sure that adding some junk in a controlled manner is the
only cheap and rather-reliable way to get something..

Not sure if that will help, but what I was playing with some stuff in
the lines of:
-- Store the length up to page boundary.
select setting::int - ((pg_current_wal_insert_lsn() - '0/0') %
  setting::int) as boundary from pg_settings where name = 'wal_block_size'
  \gset
-- Generate record up to boundary (56 bytes for base size of the record,
-- stop at 12 bytes before the end of the page.
select pg_logical_emit_message(false, '', repeat('a', :boundary - 56 - 12));

Then by injecting some FF's on the last page written and forcing
replay I am able to force some of the error code paths, so I guess
that's what you were basically doing?
--
Michael