From: Simon J Mudd
Date: October 16 2008 9:52am
Subject: Re: REPLICATION
List-Archive: http://lists.mysql.com/replication/1482
Message-Id: <20081016095228.GA23416@ams03.wl0.org>
MIME-Version: 1.0
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Please don't cc me: I'm subscribed to the list.

On Thu, Oct 16, 2008 at 10:06:20AM +0100, Marcus Bointon wrote:
> On 16 Oct 2008, at 09:46, Simon J Mudd wrote:
> 
> >If they are on 2 instances then they are not on the same slave, so the
> >answer is definitely no.
> 
> Not true. Simply run the two instances on different ports and  
> different config files.

Then you are not replicating from 2 separate masters into the same
instance which is what the questioner was asking.

MySQL allows you to do:

           /--------> slave 1
          /
master  ------------> slave 2
          \
           \--------> slave 3

Whether these slaves are located on the same server or not is irrelevant.

What it doesn't allow you to do is:

master 1 --\ 
            \
master 2 ------> common slave instance
            /
master 3 --/ 

Thus the "common slave instance" acts as a central server containing all
the data from the 3 masters shown in the example. To do this requires
careful configuration to ensure you avoid duplicate rows but can be done,
but not AFAIK in MySQL.

Simon