Re: Function to promote standby servers

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
Cc: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Function to promote standby servers
Date: 2018-10-22 06:01:13
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On Sat, Oct 20, 2018 at 01:48:56PM +0900, Michael Paquier wrote:
> On Sat, Oct 20, 2018 at 06:24:28AM +0200, Laurenz Albe wrote:
>> Here is another version, with a fix in pg_proc.dat, an improved comment
>> and "wait_seconds" exercised in the regression test.
> Thanks for the new version. This looks pretty good to me. I'll see if
> I can review it once and then commit.
>> } WaitEventIPC;
> Those are kept in alphabetical order. Individual wait events are also
> documented with a description.

Regarding the documentation, wouldn't it be more adapted to list the new
function under the section "Recovery Control Functions"? Not only does
the new function signal the postmaster, but it also creates the
promotion trigger file.

Anyway, I have been looking in depth at the patch, and I finish with the
attached. Here are some notes:
- pg_ctl returns an error if it cannot create the promote trigger file
and if it doesn't close it. pg_promote should do the same.
- WL_TIMEOUT could have been reached, leading to no further retries
(remove for example the part related to the trigger file creation and
try to trigger the promotion, the wait time is incorrect).
- Documentation has been reworked.
- The new wait event is documented.
- a WARNING is returned if the signal to the postmaster is not sent,
which is something I think makes most sense as we do the same for other
- position including unistd.h was not correct in xlogfuncs.c.
- Timeouts for the tests are made a tad longer. Some buildfarm machines
don't like a promotion wait of 10s.
- a catalog version bump is included, just a personal reminder..
- Indentatio has been run.

Laurenz, what do you think?

Attachment Content-Type Size
promote-func.patch text/x-diff 13.6 KB

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