Re: Rename max_parallel_degree?

From: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Julien Rouhaud <julien(dot)rouhaud(at)dalibo(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Josh Berkus <josh(at)agliodbs(dot)com>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Rename max_parallel_degree?
Date: 2016-10-24 20:04:24
Message-ID: ac601d90-0a3f-5307-7132-bdf934712cce@2ndquadrant.com
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On 10/12/16 7:58 PM, Robert Haas wrote:
> I don't think it's wrong that the handling is done there, though. The
> process that is registering the background worker is well-placed to
> check whether there are already too many, and if it does not then the
> slot is consumed at least temporarily even if it busts the cap. On
> the flip side, the postmaster is the only process that is well-placed
> to know when a background worker terminates. The worker process
> itself can't be made responsible for it, as you suggest below, because
> it may never even start up in the first place (e.g. fork() returns
> EAGAIN). And the registering process can't be made responsible,
> because it might die before the worker.

Those are valid technical points. I have not worked out any alternatives.

I'm concerned that all this makes background workers managed by
extensions second-class citizens.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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