Post-Start script Fails After Modifying max_binlog_cache_size

Products

• VMware Tanzu for MySQL

Issue/Introduction

When deploying or upgrading a MySQL instance created by VMware Tanzu for MySQL on Cloud Foundry (CF), the deployment halts, and the post-start job fails.

In mysql job post-start.stdout.log, you may see errors indicating that the thermostat health check has failed.

Dedicated MySQL replication replication options [It] bin log max cache size is set to 2G
/var/vcap/data/compile/thermostat/thermostat/thermostat_test.go:317
 
  [FAILED] Expected
<string>: ###########
  to equal
<string>: 2147483648
  In [It] at: /var/vcap/data/compile/thermostat/thermostat/thermostat_test.go:300 @ 05/01/25 11:21:21.404

The Tanzu for MySQL thermostat component validates the runtime MySQL configuration against the expected defaults defined in the my.cnf file.

• By default, my.cnf explicitly defines max-binlog-cache-size = 2G (2147483648 bytes).

• If a database administrator or custom application modifies the max_binlog_cache_size value dynamically (for example, via a stored procedure), a mismatch occurs.

• Because the active runtime value no longer matches the expected 2G threshold, the thermostat health check fails and intentionally blocks the deployment/startup process to prevent configuration drift.

Environment

Tanzu for MySQL on CF 

• 3.x
• 10.0.x

 

 

Resolution

Permanent Fix

Upgrade to VMware Tanzu for MySQL on CF 10.1 or above. Version 10.1 and higher include architectural updates that prevent this specific runtime configuration mismatch from blocking the deployment process.

Workaround (If an immediate upgrade is not possible)

If you cannot upgrade your Tanzu for MySQL tile at this time, use the following steps to temporarily bypass the issue during deployments or updates:

1. Drop the Procedure: Temporarily remove or drop the stored procedure (or automation script) that alters the max_binlog_cache_size variable.

2. Reset the Value: Ensure max_binlog_cache_size is manually reverted to its default value of 2147483648 (2G).

3. Run the Deployment: Complete your Tanzu for MySQL instance upgrade, patch, or CF deployment.

4. Reapply the Procedure: Once the deployment successfully finishes and the post-start jobs pass, recreate the stored procedure to re-apply your custom configuration.

Note: This workaround must be repeated for any subsequent tile upgrades or instance recreations until the platform is upgraded to version 10.1 or higher.