aws_rds_cluster_parameter_group shows an unintended diff about time_zone

[chroju]

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Terraform Version

Terraform v0.12.28
+ provider.aws v2.69.0

Affected Resource(s)

• aws_rds_cluster_parameter_group

Terraform Configuration Files

resource "aws_rds_cluster_parameter_group" "sample" {
  name   = "sample"
  family = "aurora-mysql5.7"

  parameter {
    name         = "time_zone"
    value        = "Asia/Tokyo"
    apply_method = "immediate"
  }

}

Debug Output

Nothing.

Panic Output

Nothing.

Expected Behavior

Once we run terraform apply and then run terraform plan, the result should be no changes.

Actual Behavior

The difference is displayed as follows.

      + parameter {
          + apply_method = "immediate"
          + name         = "time_zone"
          + value        = "Asia/Tokyo"
        }
      - parameter {
          - apply_method = "immediate" -> null
          - name         = "time_zone" -> null
          - value        = "asia/tokyo" -> null
        }

Since it's not possible to set time_zone to lowercase, I suspect this is a bug. I think this is due to the ToLower() in the flattenParameters() function.

https://github.com/terraform-providers/terraform-provider-aws/blob/2b183022f881e6ccb0d2a1cb0a750f52daf89d5d/aws/structure.go#L931-L950

Steps to Reproduce

1. terraform apply
2. terraform plan

Important Factoids

Nothing.

References

[acdha]

#15583 appears to be the same underlying issue

[bill-rich]

Hi @chroju! I was trying to reproduce this issue, but was not able to with provided configuration. If you're still seeing this issue, can you post a config that I can use to test a fix?

[chroju]

Hi @bill-rich . I tried to reproduce this problem again.

The config to reproduce the problem is as follows.

resource "aws_rds_cluster_parameter_group" "test1" {
  name   = "test1"
  family = "aurora-mysql5.7"


  parameter {
    name         = "time_zone"
    value        = "UTC"
    apply_method = "immediate"
  }

  parameter {
    name         = "server_audit_logging"
    value        = "0"                       # this is same as the default value
    apply_method = "immediate"
  }
}

resource "aws_rds_cluster_parameter_group" "test2" {
  name   = "test2"
  family = "aurora-mysql5.7"


  parameter {
    name         = "time_zone"
    value        = "UTC"
    apply_method = "immediate"
  }
}

Once you have run apply, run plan. The result is as follows.

  # aws_rds_cluster_parameter_group.test will be updated in-place
  ~ resource "aws_rds_cluster_parameter_group" "test1" {
        id          = "test1"
        name        = "test1"
        tags        = {}
        # (3 unchanged attributes hidden)

      + parameter {
          + apply_method = "immediate"
          + name         = "server_audit_logging"
          + value        = "0"
        }
      + parameter {
          + apply_method = "immediate"
          + name         = "time_zone"
          + value        = "UTC"
        }
      - parameter {
          - apply_method = "immediate" -> null
          - name         = "time_zone" -> null
          - value        = "utc" -> null
        }
    }

Plan: 0 to add, 1 to change, 0 to destroy.

This behavior is probably caused by the difference in server_audit_logging, Because the test2 resource with only time_zone parameter does not show the diff.

Therefore, my initial thought that the diff might be caused by the letter case seems to be wrong. When there is some other diff, the difference in letter case will also be shown as an unintended diff.

This can be reproduced with any parameter other than server_audit_logging . For example, I have confirmed that it can be reproduced by setting aurora_binlog_read_buffer_size to 5242880 (same as the default value).

So, in my case, there are two problems.

• When there is some other diff, the difference in letter case will also be shown as an unintended diff. (This issue)
• When the same value as the default value is set to parameter, the difference is wrong. (Another issue, maybe aws_rds_cluster_parameter_group plan shows changes after applying #5410 )

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[github-actions]

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