7.5.10.3 Additional Information

Protocol and Execution Limitations

MySQL REST Service component uses the existing MRS HTTP API and JSON or media response formats. It does not expose the MySQL client/server protocol or accept arbitrary client-supplied SQL.

A REST procedure or function configured with mysqlTask.driver = "router" is not supported in component mode. Invoking such an endpoint returns HTTP 501 Not Implemented.

The component's worker threads are not associated with a THD for their complete lifetime. A server session and THD are used only while SQL executes. The component does not provide explicit Performance Schema instrumentation.

Logging

MySQL REST Service messages are routed to the MySQL Server error log.

SYSTEM messages are written at the server system level. FATAL and ERROR messages map to server errors. WARNING maps to server warnings. INFO, NOTE, and DEBUG map to server information messages.

The logging threshold is initialized from log_error_verbosity when the component starts. The default value of 2 omits INFO, NOTE, and DEBUG messages. Set log_error_verbosity to 3 before component startup to include them. Error-log filters, including the log_filter_dragnet component, may filter messages further.

Replication

MySQL REST Service component configuration, status, and lifecycle operations are instance-local. MySQL Server 26.10 supports one active component-hosted MRS runtime on the writable source or primary.

MySQL REST Service component does not detect replication role changes, coordinate failovers, redirect REST traffic, transfer connections, or provide active-active coordination between component instances. The component does not bypass read_only or super_read_only. If a required metadata write is rejected, startup returns an ERROR and must be retried after the cause is corrected.

Before starting MySQL REST Service on a promoted replica, stop or fence the previous primary, ensure that the replicated internal accounts and metadata are valid, and retry startup directly on the promoted server. Automatic promotion handling and traffic switching are not provided.

MySQL Router

Component-hosted and Router-hosted MySQL REST Service may read the same persistent REST definitions and application data during a controlled transition, but they are not a coordinated active-active deployment. Each runtime must have a distinct listener endpoint and registration identity. HTTP sessions, cookies, JWTs, caches, and in-flight requests are local to the issuing runtime and are not transferred. Clients moved between runtimes must authenticate again.

To migrate from Router-hosted to component-hosted MySQL REST Service, do the following:

1. Verify that the MRS metadata version, provider-role grants, published services, listener port, and registration identity are valid for the component.

2. Stop directing new requests to Router-hosted MRS and stop its MRS endpoint.

3. Install the component and wait for mysql_rest_service.state to become READY.

4. Validate the published services through the component endpoint.

5. Update client URLs, proxy or DNS routing, and TLS trust.

6. Retain MySQL Router if it is still required for MySQL protocol routing, topology discovery, load balancing, or failover.