Thread: Better error messages when lacking connection slots for autovacuumworkers and bgworkers
Better error messages when lacking connection slots for autovacuumworkers and bgworkers
From
Michael Paquier
Date:
Hi all, When lacking connection slots, the backend returns a simple "sorry, too many clients", which is something that has been tweaked by recent commit ea92368 for WAL senders. However, the same message would show up for autovacuum workers and bgworkers. Based on the way autovacuum workers are spawned by the launcher, and the way bgworkers are added, it seems that this cannot actually happen. Still, in my opinion, providing more context can be helpful for people trying to work on features related to such code so as they can get more information than what would normally happen for normal backends. I am wondering as well if this could not help for issues like this one, which has popped out today and makes me wonder if we don't have race conditions with the way dynamic bgworkers are spawned: https://www.postgresql.org/message-id/CAONUJSM5X259vAnnwSpqu=VnRECfGSJ-CgRHyS4P5YyRVwkXsQ@mail.gmail.com There are four code paths which report the original "sorry, too many clients", and the one of the patch attached can easily track the type of connection slot used which helps for better context messages when a process is initialized. Would that be helpful for at least debugging purposes? Thanks, -- Michael
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Re: [Suspect SPAM] Better error messages when lacking connectionslots for autovacuum workers and bgworkers
From
Kyotaro HORIGUCHI
Date:
Hello. At Wed, 13 Feb 2019 14:13:09 +0900, Michael Paquier <michael@paquier.xyz> wrote in <20190213051309.GF5746@paquier.xyz> > Hi all, > > When lacking connection slots, the backend returns a simple "sorry, > too many clients", which is something that has been tweaked by recent > commit ea92368 for WAL senders. However, the same message would show > up for autovacuum workers and bgworkers. Based on the way autovacuum > workers are spawned by the launcher, and the way bgworkers are added, > it seems that this cannot actually happen. Still, in my opinion, > providing more context can be helpful for people trying to work on > features related to such code so as they can get more information than > what would normally happen for normal backends. I agree to the distinctive messages, but the autovaccum and bgworker cases are in a kind of internal error, and they are not "connection"s. I feel that elog is more suitable for them. > I am wondering as well if this could not help for issues like this > one, which has popped out today and makes me wonder if we don't have > race conditions with the way dynamic bgworkers are spawned: > https://www.postgresql.org/message-id/CAONUJSM5X259vAnnwSpqu=VnRECfGSJ-CgRHyS4P5YyRVwkXsQ@mail.gmail.com > > There are four code paths which report the original "sorry, too many > clients", and the one of the patch attached can easily track the > type of connection slot used which helps for better context messages > when a process is initialized. > Would that be helpful for at least debugging purposes? I agree that it is helpful. Errors with different causes ought to show distinctive error messages. regards. -- Kyotaro Horiguchi NTT Open Source Software Center
Re: [Suspect SPAM] Better error messages when lacking connectionslots for autovacuum workers and bgworkers
From
Michael Paquier
Date:
On Thu, Feb 14, 2019 at 09:04:37PM +0900, Kyotaro HORIGUCHI wrote: > I agree to the distinctive messages, but the autovaccum and > bgworker cases are in a kind of internal error, and they are not > "connection"s. I feel that elog is more suitable for them. I used ereport() for consistency with the existing code, still you are right that we ought to use elog() as this is the case of a problem which should not happen. -- Michael