Re: Automatic Client Failover

From: Markus Wanner <markus(at)bluegap(dot)ch>
To: Dimitri Fontaine <dfontaine(at)hi-media(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, josh(at)agliodbs(dot)com, Simon Riggs <simon(at)2ndquadrant(dot)com>
Subject: Re: Automatic Client Failover
Date: 2008-08-05 10:56:19
Message-ID: 489831D3.3030800@bluegap.ch
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Hi,

Dimitri Fontaine wrote:
> If slave nodes were able to accept connection and redirect them to master, the
> client wouldn't need to care about connecting to master or slave, just to
> connect to a live node.

I've thought about that as well, but think about it this way: to protect
against N failing nodes, you need to forward *every* request through N
living nodes, before actually hitting the node which processes the
query. To me, that sounds like an awful lot of traffic within the
cluster, which can easily be avoided with automatic client failover.

(Why are you stating, that only slaves need to redirect? What is
happening in case of a master failure?)

> So the proposal for Automatic Client Failover becomes much more simpler.

I'm arguing it's the other way around: taking down a node of the cluster
becomes much simpler with ACF, because clients automatically reconnect
to another node themselves. The servers don't need to care.

Regards

Markus Wanner

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