Changes in MySQL Router 9.4.0 (2025-07-22, Innovation Release)

Note

These release notes were created with the assistance of MySQL HeatWave GenAI.

Important

MySQL Router now features full support for MySQL REST Service in on-premise configurations. See the announcement blog post HeatWave REST Service and the Quick Start Guide for details about MySQL REST Service.

• Deprecation and Removal Notes

• Functionality Added or Changed

• Bugs Fixed

Deprecation and Removal Notes

• As of this version, MySQL Router's HTTP/2 feature is disabled, to allow for future refactoring. (Bug #38055103)

Functionality Added or Changed

• MySQL Router now generates SSL certificates with a validity period of one year, aligning with best practices that recommend a validity period of no more than 397 days. This change affects the auto-generated certificates created during the bootstrap process. Error messages related to certificate validity may be encountered if using previously generated certificates with longer validity periods. (Bug #37936725)

Bugs Fixed

• MySQL Router's logger created a lock on every log call, even if logging was disabled.

  As of this release, the logger now acquires locks only when logging is enabled. (Bug #38044378)

• Fixed an issue related to debug logging. (Bug #38009073)

• Users created with a comment in their definition were unable to connect using MySQL Router. Error messages were returned similar to the following:

  ERROR 1045 (28000): Access denied

  (Bug #37903358)

• Routing Guidelines, introduced in 9.2.0, did not treat bind_address=localhost as a valid target when generated from the MySQL Router configuration. (Bug #37844427)

• It was not possible to build MySQL Router with GCC 15 on Fedora 42 due to missing includes. (Bug #37769606)

• After a DNS failure, the destination was not added to quarantine and could not be checked for availability after the connection was restored. Errors were returned similar to the following:

          resolve(host) failed: Name or service not known

  (Bug #37617712)

• Under certain circumstances, with Connection Sharing enabled, MySQL Router could crash due to a race condition in the connection pool. MySQL Router tried to close a connection while also making that connection available to another thread. Errors were returned similar to the following:

  Process Core Dump (PID XXXXXX/UID 0) 
  Resource limits disable core dumping for process XXXXXX (mysqlrouter)

  (Bug #37303055)