MySQL 8.2 Finally Supports Read/Write Splitting

MySQL InnoDB ReplicaSet

The article starts by describing a minimal InnoDB ReplicaSet architecture, which consists of a single source instance and one or more asynchronous replicas. Screenshots show the ReplicaSet object status in MySQL Shell.

Starting MySQL Router 8.2

Next, the author configures and launches MySQL Router 8.2. Images illustrate the Router configuration steps and the Router view inside the MySQL Shell ReplicaSet object.

Demonstrating Read/Write Routing

Connecting to the Router on port 6450, the author shows that read operations are automatically directed to a replica, while a transaction start forces routing to the source (primary) without changing the port. A separate screenshot demonstrates the behavior of read‑only transactions.

Router Configuration for Split Routing

The generated Router configuration file contains a bootstrap_rw_split section that enables read/write splitting:

[routing:bootstrap_rw_split]
bind_address=0.0.0.0
bind_port=6450
destinations=metadata-cache://myreplica/?role=PRIMARY_AND_SECONDARY
routing_strategy=round-robin
protocol=classic
connection_sharing=1
client_ssl_mode=PREFERRED
server_ssl_mode=PREFERRED
access_mode=auto

The article also notes that the ROUTER SET access_mode= command can be used in a session to explicitly choose the instance type to access.

Conclusion

MySQL Router 8.2’s read/write splitting is a valuable feature that optimizes database performance and scalability while eliminating the need for application‑level routing logic. All read traffic is directed to read‑only replicas, and all write traffic goes to the primary source, simplifying deployment and management.