| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: The way to know whether the standby has caught up with the master |
| Date: | 2011-05-25 11:34:59 |
| Message-ID: | BANLkTimopsxjt-OPr7Z62D7q7c_-E4Ao=g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, May 25, 2011 at 6:16 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>> To achieve that, I'm thinking to change walsender so that, when the
>> standby
>> has caught up with the master, it sends back the message indicating that
>> to
>> the standby. And I'm thinking to add new function (or view like
>> pg_stat_replication)
>> available on the standby, which shows that info.
>
> By the time the standby has received that message, it might not be caught-up
> anymore because new WAL might've been generated in the master already.
AFAICS, this is an exact case of the Byzantine General's problem.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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