aws-rds: removing parameter from parameter group does not set it to the default value

[ChrisLane]

Describe the bug

I am unable to set a parameter group parameter to its default value without setting it explicitly in CDK.

Expected Behavior

When I remove a parameter from a CDK created parameter group, I expect that parameter to be handled by the AWS defaults as if I had pressed "Set to default value" for the parameter in the AWS Management Console.

Current Behavior

When a parameter is removed from a parameter group in AWS CDK, it remains as the same value in AWS Management Console.

Reproduction Steps

Deploy a parameter group with the following JavaScript code:

    const mysql8ParameterGroupParameters = {
      character_set_client: "utf8",
      character_set_connection: "utf8",
      character_set_database: "utf8",
      character_set_filesystem: "utf8",
      character_set_results: "utf8",
      character_set_server: "utf8",
      collation_connection: "utf8_unicode_ci",
      collation_server: "utf8_unicode_ci",
      innodb_strict_mode: "1"
    };
      const mysql8DatabaseClusterParameterGroup = new rds.CfnDBClusterParameterGroup(
          this,
          "mysql-8-database-cluster-parameter-group",
          {
            dbClusterParameterGroupName: `myParamGroup`,
            family: "aurora-mysql8.0",
            parameters: mysql8ParameterGroupParameters
          });

Then remove all the collation.. and character_set... parameters and deploy the changes.
Observe that the parameters are still set to utf8 in AWS Management Console rather than the defaults.

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.129.0

Framework Version

No response

Node.js Version

v21.6.2

OS

Mac OS

Language

TypeScript

Language Version

JavaScript

Other information

No response

[pahud]

I created a new parameter group like this without specifying some props(comment off):

    const mysql8ParameterGroupParameters3 = {
      // character_set_client: "utf8",
      // character_set_connection: "utf8",
      // character_set_database: "utf8",
      // // character_set_filesystem: "utf8",
      // character_set_results: "utf8",
      // character_set_server: "utf8",
      collation_connection: "utf8_unicode_ci",
      collation_server: "utf8_unicode_ci",
      innodb_strict_mode: "1"
    };

    const mysql8DatabaseClusterParameterGroup = new rds.CfnDBClusterParameterGroup(
      this,
      "mysql-8-database-cluster-parameter-group",
      {
        dbClusterParameterGroupName: `myParamGroup`,
        family: "aurora-mysql8.0",
        parameters: mysql8ParameterGroupParameters,
        description: 'test',
      });

And I check character_set_client and character_set_connection from the RDS console. Their values are all utf8.

Can you be specific and tell me which attribute should not be utf8 by default so I can investigate it further?

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[ChrisLane]

@pahud By default, the parameters should appear as blank in the management console like in this screenshot.

This is what I would expect to see if CDK had the correct behaviour.

[pahud]

If you do not specify those attributes, CDK would not synthesize for that explicitly and the default values would be determined by CFN, not CDK. I am afraid this is not something CDK can do. What do you think?

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This issue has not received a response in a while. If you want to keep this issue open, please leave a comment below and auto-close will be canceled.