Amazon RDS two way replication

Question

I have two rds which have the same structure, each db serves one of two apps. Some of tables are using by first app some by other. I want to set up two ways read/write replication between two rds. I can do it with stand alone mysql, set table replication ( https://dev.mysql.com/doc/refman/5.7/en/replication-rules-table-options.html ) but can not find any option to do so for rds

Answer 1

This is is probably what you'd call a Really Bad Idea™.

RDS does allow you to configure an RDS instance as a slave of another machine.

http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/mysql_rds_set_external_master.html

Of course, on the same page...

Warning

Do not use mysql.rds_set_external_master to manage replication between two Amazon RDS DB instances.

...however, that appears to be because that's not how you configure an RDS instance to be a replica of another instance. When you're configuring a read-only replica, you don't use this -- RDS manages all of the replication configuration for you.

mysql.rds_set_external_master() is a stored procedure that allows you to execute CHANGE MASTER TO... since, in RDS, you lack the SUPER privilege and would otherwise be unable to do this.

The feature is designed for hot migrations from a non-RDS MySQL server to RDS, by replicating the events from the external master into RDS during the transition.

...however, if there is a way to do what you are trying to do with RDS, this would be it. Each instance would be set to use the other as its master.

The two would need to have network connectivity, which means they'd need to be in the same region and same VPC, or you'd have to handle the peering or tunnel configuration yourself to establish that network path.

This is almost certainly an unsupported configuration, but again, if there is a way to accomplish it, this would be the way. "Unsupported" doesn't mean it won't work, but only that AWS support will not likely be able to provide assistance if it doesn't.

Did I mention this might not be a good idea?