From: | Bruce Momjian <bruce(at)momjian(dot)us> |
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To: | Shaun Thomas <sthomas(at)optionshouse(dot)com> |
Cc: | Daniel Farina <daniel(at)heroku(dot)com>, Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Synchronous Standalone Master Redoux |
Date: | 2012-07-12 17:02:23 |
Message-ID: | 20120712170223.GB11063@momjian.us |
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Lists: | pgsql-hackers |
On Thu, Jul 12, 2012 at 08:21:08AM -0500, Shaun Thomas wrote:
> >But, putting that aside, why not write a piece of middleware that
> >does precisely this, or whatever you want? It can live on the same
> >machine as Postgres and ack synchronous commit when nobody is home,
> >and notify (e.g. page) you in the most precise way you want if nobody
> >is home "for a while".
>
> You're right that there are lots of ways to kinda get this ability,
> they're just not mature enough or capable enough to really matter.
> Tailing the log to watch for secondary disconnect is too slow. Monit
> or Nagios style checks are too slow and unreliable. A custom-built
> middle-layer (a master-slave plugin for Pacemaker, for example) is
> too slow. All of these would rely on some kind of check interval.
> Set that too high, and we get 10,000xn missed transactions for n
> seconds. Too low, and we'd increase the likelihood of false
> positives and unnecessary detachments.
Well, the problem also exists if add it as an internal database feature
--- how long do we wait to consider the standby dead, how do we inform
administrators, etc.
I don't think anyone says the feature is useless, but is isn't going to
be a simple boolean either.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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