EOI - Linux Developer required

David Lloyd lloy0076 at adam.com.au
Wed Jan 10 10:35:20 CST 2007


Q: What issues should I be aware of when setting up two-way replication?

A: MySQL replication currently does not support any locking protocol 
between master and slave to guarantee the atomicity of a distributed 
(cross-server) update. In other words, it is possible for client A to 
make an update to co-master 1, and in the meantime, before it propagates 
to co-master 2, client B could make an update to co-master 2 that makes 
the update of client A work differently than it did on co-master 1. 
Thus, when the update of client A makes it to co-master 2, it produces 
tables that are different from what you have on co-master 1, even after 
all the updates from co-master 2 have also propagated. This means that 
you should not chain two servers together in a two-way replication 
relationship unless you are sure that your updates can safely happen in 
any order, or unless you take care of mis-ordered updates somehow in the 
client code.


...it's possible, but it makes the A in ACID more complex than it need be.


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