Re: Support for N synchronous standby servers - take 2

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Beena Emerson <memissemerson(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Support for N synchronous standby servers - take 2
Date: 2016-04-08 11:02:55
Message-ID: CAA4eK1KUi=ps5H1UEOJB+40Kcah-whjTOezmzWQ2ZNB5oJyq7A@mail.gmail.com
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On Thu, Apr 7, 2016 at 5:49 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>
> On Thu, Apr 7, 2016 at 7:29 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:
> >
> > So if we go by this each time backend calls pg_stat_get_wal_senders, it
> > needs to do parsing to form SyncRepConfig whether it's changed or not
from
> > previous time. I understand that this is not a performance critical
path,
> > but still if we can do it in some other optimal way which doesn't hurt
any
> > other path, then it will be better.
>
> So, will you write the patch? Either current implementation or
> the approach you're suggesting works to me. If you really want
> to change the current one, I'm happy to review that.
>

Sorry, I don't have time to complete the patch, but I have written an
initial patch to show you what I have in mind and something on this lines
should work. I think with such an approach, you don't need to parse for
s_s_names twice (once in check_* and once in syncupdate* function), you
can refer check_temp_tablespaces() and assign_temp_tablespaces() to see how
to use the work done by check_* function in assign_* function. Also write
now, I have used TopMemoryContext for allocation in
assign_synchronous_standby_names, it is better to use guc_malloc or
something similar for allocation as is done in other check_* and assign_*
functions.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

Attachment Content-Type Size
fix_sync_rep_update_conf_v1.patch application/octet-stream 3.3 KB

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