From: Shawn Green
Date: September 24 2012 6:05pm
Subject: Re: Doubt Regd. Circular Replication In Mysql
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Hello Benjamin,

On 9/24/2012 10:52 AM, Stillman, Benjamin wrote:
> replicate-same-server-id = 0 keeps MySQL from replicating binary log entries from itself. For instance, here's a rough overview:
>
> You write to Server A.
> Server A writes that to its binary log.
> Server B reads Server A's binary log and completes the same thing.
> Because log-slave-updates is enabled, Server B writes it to its own binary log.
> Server C reads Server B's binary log and completes the same thing.
> Again, with log-slave-updates enabled, Server C writes it to its own binary log.
> Server A reads Server C's binary log.
>
> Here's where the issue starts. Without replicate-same-server-id = 0, Server A will complete the insert/update/delete as it reads it from Server C's binary log. However, this query originated from Server A, so it's just going to do it again. Then it's again replicated to Server B, Server C, and so on. This can create a loop and/or break replication. For instance, if you drop a table on A. It replicates across, and back to A. Replication will error out because when it tries to drop the same table again, it already doesn't exist. You need replicate-same-server-id = 0 set so that it knows not to execute any binary log entries with its own server ID.
>

Not true.

Replication, by default, operates with --replicate-same-server-id=0. The 
only time you need to change it to a 1 is for certain recovery 
scenarios. We added this variable specifically to allow for exceptions 
to the rule that every server in a replication chain (or ring) must have 
their own, unique, --server-id value.

It's not required for normal operations. In fact we recommend you do not 
set it at all. Each server will automatically ignore any event that 
originates from a server with the same --server-id setting unless you 
specifically set --replicate-same-server-id=1 .

Regards
-- 
Shawn Green
MySQL Principal Technical Support Engineer
Oracle USA, Inc. - Hardware and Software, Engineered to Work Together.
Office: Blountville, TN