Re: Replication pointers

[Chis Florinel]

Brian Aker:


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It is safe to connect servers in a circular master/slave relationship with the --log-slave-updates option specified. Note, however, that many statements do not work correctly in this kind of setup unless your client code is written to take care of the potential problems that can occur from updates that occur in different sequence on different servers.

This means that you can create a setup such as this:

A -> B -> C -> A

Server IDs are encoded in the binary log events, so server A knows when an event that it reads was originally created by itself and does not execute the event (unless server A was started with the --replicate-same-server-id option, which is meaningful only in rare setups). Thus, there are no infinite loops. But this circular setup works only if you perform no conflicting updates between the tables. In other words, if you insert data in both A and C, you should never insert a row in A that may have a key that conflicts with a row inserted in C. You should also not update the same rows on two servers if the order in which the updates are applied is significant.

http://dev.mysql.com/doc/mysql/en/replication-features.html