Constraints on Database Proxy

Unsupported functions

• Proxy instances do not support compression protocols.
• Proxy instances do not support the READ-UNCOMMITTED transaction isolation level.
• Proxy instances only support permission verification at the database level, not at the individual table level.
• Proxy instances do not support SHOW ERRORS or SHOW WARNINGS commands.

HTAP analysis

• Consistency levels and connection pooling are not supported.
• Only the weighted routing policy is supported.
• Only the read/write mode is allowed for proxy instances.
• If a proxy instance is associated with an HTAP instance, the account and password created on the HTAP instance must be the same as those used to connect to the proxy instance. Otherwise, requests cannot be distributed to this HTAP instance through the proxy instance.

Usage constraints

• Read/write splitting can be enabled only when at least one read replica is created.
• After read/write splitting is enabled, the database port of your TaurusDB instance cannot be changed.
• Deleting a TaurusDB instance with read/write splitting enabled will also delete its proxy instance.
• rdsProxy is a built-in database proxy account. To ensure that read/write splitting functions properly, do not create any account with the same name as rdsProxy.
• Read/write splitting does not support the caching_sha2_password identity authentication plugin provided in MySQL 8.0.
• To prevent a proxy instance from consuming too many resources to parse SQL statements, a maximum of 100 SQL statements can be committed and executed in a batch, and the size of a concatenate SQL statement cannot exceed 100 MB.
• When a .NET client is used to connect to database proxies, the client's MySQL.Data driver version must be 8.0.19 or later because earlier driver versions may be incompatible with database proxies.

Syntax Constraints

• The output of show processlist executed through a proxy address differs from that executed directly on a TaurusDB instance. A proxy instance's show processlist displays only the requests routed through its proxy nodes.
• If a proxy node is abnormal, running show processlist or kill on the proxy instance may take an extended period, but your workloads will not be affected.
• If a proxy node is deleted, requests routed through this deleted node may be displayed in the output of show processlist executed on the proxy instance.
• If kill is executed on the proxy instance, error information such as timeout may be displayed occasionally. You can run show processlist again to check whether the services are killed successfully.
• If a proxy node is abnormal, there may be frame freezing for 2 seconds when you run SHOW PROCESSLIST. The results will still be returned.
• With a read/write splitting address used, if stored procedures and functions rely on user variables (@variable), the execution results may be incorrect.
• Enabling session-level connection pooling will cause SELECT LAST_INSERT_ID() to consistently return 0.