This topic describes the notes that you must understand before you use the dedicated proxy feature of ApsaraDB RDS for MySQL.
- When you change the specifications of the primary RDS instance or read-only RDS instances, you may experience a transient connection.
- If your application connects to your database system by using a proxy endpoint and the transaction splitting feature is not enabled, all requests that are encapsulated in transactions are routed to the primary RDS instance.
- If a proxy endpoint is used to implement read/write splitting, the read consistency of the requests that are not encapsulated in transactions cannot be ensured. If you want to ensure the read consistency of these requests, you must encapsulate these requests in transactions or add hints. For more information, see Execute hints on an ApsaraDB RDS for MySQL instance.
- If your application connects to your database system by using a proxy endpoint, the
SHOW PROCESSLISTstatement returns a result set for each query. The result set consists of the query results from the primary RDS instance and read-only RDS instances.
- If you run multi-statement queries or stored procedures, the read/write splitting feature is disabled. In this case, all the subsequent requests over the current connection are routed to the primary RDS instance. To enable the read/write splitting feature again, you must close the current connection and establish a new connection. For more information about multi-statement queries, see Multi-Statement.
- The dedicated proxy uses the 1:N connection model. After your application initiates a connection request, the dedicated proxy replicates the established connection to the primary RDS instance and all the read-only RDS instances. The maximum number of connections to the dedicated proxy is not limited. This number varies based on the specifications of the primary RDS instance and read-only RDS instances. If you do not enable the transaction connection pool feature, the dedicated proxy establishes a connection to each of the primary RDS instance and read-only RDS instances after the dedicated proxy receives a request from your application. After you enable the dedicated proxy, we recommend that you specify the same connection specifications for the primary RDS instance and read-only RDS instances. If these instances have different connection specifications, the number of allowed connections is subject to the lowest connection specifications among these instances.
- If you create or restart a read-only RDS instance after you enable the dedicated proxy feature, only the requests over a new connection are routed to the new or restarted read-only RDS instance.
- The max_prepared_stmt_count parameter must be set to the same value for the primary RDS instance and read-only RDS instances
- If you use the MySQL CLI to establish a connection and execute hints, you must add the
-cparameter to these hints. If you do not add this parameter to a hint, the MySQL CLI filters the hint out. For more information about the hint syntax, see Execute hints on an ApsaraDB RDS for MySQL instance.
- If the primary RDS instance is locked, the enabled proxy instances are not released but can process only read requests.
- If the primary RDS instance is released, the enabled proxy instances are automatically released. You are no longer charged for the dedicated proxy feature.