Is it possible to create a multi source read replica in RDS

Question

We use RDS MySQL with a micro service architecture. Each service has its own database and we have been slowly moving them into their own instances for load management and whatnot.

We have a replica still attached to the primary instance (where most of the databases still reside) but it is missing the databases that are on their own instances. We would like to have a single read replica that sources from all of the instances so that we can run sanity checks on the data without needing to move data between instances.

Does RDS support a multi source read replica? Or will we need to manage our own MySQL install in order to accomplish this?

Answer 1

As far as I know, you will have to operate MySQL yourself on EC2 to get the multi-source replication feature. You may like to contact your AWS support representative to confirm this.

AWS RDS does not support multi-source replication. Configuring replication from an external master is limited because you have to configure it using a stored procedure provided by AWS. It does not have any support for configuring multiple replication channels. Each replica has exactly one master.

AWS Aurora 2.x (API-compatible with MySQL 5.7) also does not support multi-source replication. As of Aurora 2.07.x, they list multi-source replication among features of MySQL 5.7 they do not support. See https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraMySQL.Updates.2070.html

AWS Aurora 1.x (API-compatible with MySQL 5.6) has something they call multi-master cluster, where all the nodes in a cluster can be writers. I have not used this, and I don't know how reliable it is. See https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-multi-master.html for details.

It's weird that they seem to have lost functionality between Aurora 1.x and 2.x. My understanding is that they sort of "started over" with Aurora 2.x, and some features haven't been implemented in the new version yet.

This is my understanding as of December 2019. Of course future versions may add such features.