6.4.3 Deploying MySQL Router

The recommended deployment of MySQL Router is on the same host as the application. When using a sandbox deployment, everything is running on a single host, therefore you deploy MySQL Router to the same host. When using a production deployment, we recommend deploying one MySQL Router instance to each machine used to host one of your client applications. It is also possible to deploy MySQL Router to a common machine through which your application instances connect. For more information, see Installing MySQL Router.

To bootstrap MySQL Router based on an InnoDB Cluster or InnoDB ReplicaSet, you need the URI-like connection string to an online instance. Run the mysqlrouter command and provide the --bootstrap=instance option, where instance is the URI-like connection string to an online instance. MySQL Router connects to the instance and uses the included metadata cache plugin to retrieve the metadata, consisting of a list of server instance addresses and their role. For example:

$> mysqlrouter --bootstrap icadmin@ic-1:3306 --account=mysqlrouter

You are prompted for the instance password and encryption key for MySQL Router to use. This encryption key is used to encrypt the instance password used by MySQL Router to connect to the cluster. The ports you can use for client connections are also displayed. For additional bootstrap related options, see Bootstrapping Options.

Tip

At this point MySQL Router has not been started so that it would route connections. Bootstrapping is a separate process.

The MySQL Router bootstrap process creates a mysqlrouter.conf file, with the settings based on the metadata retrieved from the address passed to the --bootstrap option, in the above example icadmin@ic-1:3306. Based on the metadata retrieved, MySQL Router automatically configures the mysqlrouter.conf file, including a metadata_cache section. If you are using MySQL Router 8.0.14 and later, the --bootstrap option automatically configures MySQL Router to track and store active MySQL metadata server addresses at the path configured by dynamic_state. This ensures that when MySQL Router is restarted it knows which MySQL metadata server addresses are current. For more information, see the dynamic_state documentation.

In earlier MySQL Router versions, metadata server information was defined during MySQL Router's initial bootstrap operation and stored statically as bootstrap_server_addresses in the configuration file, which contained the addresses for all server instances in the cluster. For example:

[metadata_cache:prodCluster]
router_id=1
bootstrap_server_addresses=mysql://icadmin@ic-1:3306,mysql://icadmin@ic-2:3306,mysql://icadmin@ic-3:3306
user=mysql_router1_jy95yozko3k2
metadata_cluster=prodCluster
ttl=300

Tip

If using MySQL Router 8.0.13 or earlier, when you change the topology of a cluster by adding another server instance after you have bootstrapped MySQL Router, you need to update bootstrap_server_addresses based on the updated metadata. Either restart MySQL Router using the --bootstrap option, or manually edit the bootstrap_server_addresses section of the mysqlrouter.conf file and restart MySQL Router.

The generated MySQL Router configuration creates TCP ports which you use to connect to the cluster. By default, ports for communicating with the cluster using both classic MySQL protocol and X Protocol are created. To use X Protocol the server instances must have X Plugin installed and configured, which is the default for MySQL 8.0 and later. The default available TCP ports are:

• 6446 - for classic MySQL protocol read-write sessions, which MySQL Router redirects incoming connections to primary server instances.

• 6447 - for classic MySQL protocol read-only sessions, which MySQL Router redirects incoming connections to one of the secondary server instances.

• 64460 - for X Protocol read-write sessions, which MySQL Router redirects incoming connections to primary server instances.

• 64470 - for X Protocol read-only sessions, which MySQL Router redirects incoming connections to one of the secondary server instances.

Depending on your MySQL Router configuration the port numbers might be different to the above. For example if you use the --conf-base-port option, or the group_replication_single_primary_mode variable. The exact ports are listed when you start MySQL Router.

The way incoming connections are redirected depends on the underlying topology being used. For example, when using a single-primary cluster, by default MySQL Router publishes a X Protocol and a classic MySQL protocol port, which clients connect to for read-write sessions and which are redirected to the cluster's single primary. With a multi-primary cluster read-write sessions are redirected to one of the primary instances in a round-robin fashion. For example, this means that the first connection to port 6446 would be redirected to the ic-1 instance, the second connection to port 6446 would be redirected to the ic-2 instance, and so on. For incoming read-only connections MySQL Router redirects connections to one of the secondary instances, also in a round-robin fashion. To modify this behavior see the routing_strategy option.

Once bootstrapped and configured, start MySQL Router. If you used a system wide install with the --bootstrap option then issue:

$> mysqlrouter &

If you installed MySQL Router to a directory using the --directory option, use the start.sh script found in the directory you installed to. Alternatively set up a service to start MySQL Router automatically when the system boots, see Starting MySQL Router. You can now connect a MySQL client, such as MySQL Shell to one of the incoming MySQL Router ports as described above and see how the client gets transparently connected to one of the server instances.

$> mysqlsh --uri root@localhost:6442

To verify which instance you are actually connected to, simply issue an SQL query against the port status variable.

mysql-js> \sql
Switching to SQL mode... Commands end with ;
mysql-sql> select @@port;
+--------+
| @@port |
+--------+
|   3310 |
+--------+