Horton

Re: BackendKeyData is mandatory?

Peter Eisentraut <peter@eisentraut.org>

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From: Peter Eisentraut <peter@eisentraut.org>
To: Tatsuo Ishii <ishii@postgresql.org>, pgsql-hackers@postgresql.org
Date: 2025-06-19T07:06:47Z
Lists: pgsql-hackers 
On 17.06.25 03:10, Tatsuo Ishii wrote:
> My question is, BackendKeyData is mandatory or not. Currently
> Pgpool-II raises a fatal error if BackendKeyData is not sent before
> ReadyForQuery arrives. This is because without the message, frontend
> cannot send a CancelRequest message later on, as there's no secret
> key.

I think that's fine, if the server does not want to support query 
cancellation.  The current protocol description certainly does not 
support the idea that it is a hard error *not* to send BackendKeyData.

It's also worth thinking about the new protocol 3.2 longer key data.  A 
paranoid server might choose to send key data only if protocol >=3.2 is 
chosen and not if a lower, notionally less secure version is chosen.

Commits

  1. Revert unnecessary check for NULL

  2. libpq: Be strict about cancel key lengths

  3. libpq: Handle OOM by disconnecting instead of hanging or skipping msgs

  4. libpq: Complain about missing BackendKeyData later with PGgetCancel()