Re: bug in SignalSomeChildren

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: bug in SignalSomeChildren
Date: 2010-12-17 16:18:35
Message-ID: 696.1292602715@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Is it possible to save the "is walsender" flag in the Backend struct?
> That would make it possible to solve the problem very easily.

Yeah, I was wondering about that too, but the problem is that the
postmaster doesn't know that at the time it forks the child. The
flag in shared memory will get set later, but it's hard to tell
how much later.

Of course, that observation also means that anyplace the postmaster
tries to distinguish walsenders from other children is fundamentally
broken anyhow: a walsender that hasn't set the flag yet will get
treated like a regular backend.

I think what we ought to be looking to do is get rid of the distinction,
so that the postmaster treats walsenders the same as other children.

regards, tom lane

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