From: | "Fujii Masao" <masao(dot)fujii(at)gmail(dot)com> |
---|---|
To: | "Markus Wanner" <markus(at)bluegap(dot)ch> |
Cc: | "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Bruce Momjian" <bruce(at)momjian(dot)us>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Synchronous Log Shipping Replication |
Date: | 2008-09-11 12:45:49 |
Message-ID: | 3f0b79eb0809110545w37c2080yc858a3a1d8658973@mail.gmail.com |
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Lists: | pgsql-hackers |
On Wed, Sep 10, 2008 at 11:13 PM, Markus Wanner <markus(at)bluegap(dot)ch> wrote:
>> Which signal should we use for the notification to the backend from
>> WAL sender? The notable signals are already used.
>
> I'm using SIGUSR1, see src/backend/storage/ipc/imsg.c from Postgres-R, line
> 232. That isn't is use for backends or the postmaster, AFAIK.
Umm... backends have already used SIGUSR1. PostgresMain() sets up a signal
handler for SIGUSR1 as follows.
pqsignal(SIGUSR1, CatchupInterruptHandler);
Which signal should WAL sender send to backends?
>> Or, since a backend don't need to wait on select() unlike WAL sender,
>> ISTM that it's not so inconvenient to use a semaphore for that
>> notification.
>
> They probably could, but not the WAL sender.
Yes, since WAL sender waits on select(), it's convenient to use signal
for the notification *from backends to WAL sender*, I think too.
Best regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
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