Re: Missed check for too-many-children in bgworker spawning

Robert Haas <robertmhaas@gmail.com> writes:
> On Mon, Oct 7, 2019 at 4:03 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> ... Moreover, we have to --- and already do, I trust --- deal with
>> other resource-exhaustion errors in exactly the same code path, notably
>> fork(2) failure which we simply can't predict or prevent.  Doesn't the
>> parallel query logic already deal sanely with failure to obtain as many
>> workers as it wanted?

> If we fail to obtain workers because there are not adequate workers
> slots available, parallel query deals with that smoothly.  But, once
> we have a slot, any further failure will trigger the parallel query to
> ERROR out.

Well, that means we have a not-very-stable system then.

We could improve on matters so far as the postmaster's child-process
arrays are concerned, by defining separate slot "pools" for the different
types of child processes.  But I don't see much point if the code is
not prepared to recover from a fork() failure --- and if it is, that
would a fortiori deal with out-of-child-slots as well.

            regards, tom lane