[Bug]: aws_rds_cluster major version upgrade throws InvalidParameterCombination in second apply attempt

[riji-ramachandran]

Terraform Core Version

1.0.8, 0.14.11

AWS Provider Version

4.30.0

Affected Resource(s)

aws_rds_cluster
db_instance_parameter_group_name

Expected Behavior

Trying to upgrade RDS Aurora cluster with one instance from Postgres engine version 13.7 to 14.3
apply_immediately set to true at cluster level. Also db_instance_parameter_group_name is passed to the cluster.
Expect cluster and instance to be upgraded.

Actual Behavior

On first plan and apply there are no parameter group related error. However if the first run fails for any given reason on second attempt upgrade fails with error:
Error: updating RDS Cluster: InvalidParameterCombination: The current DB instance parameter group is custom. You must explicitly specify a new DB instance parameter group, either default or custom, for the engine version upgrade
If the db_instance_parameter_group_name is changed then apply works again.

Relevant Error/Panic Output Snippet

Error: updating RDS Cluster: InvalidParameterCombination: The current DB instance parameter group is custom. You must explicitly specify a new DB instance parameter group, either default or custom, for the engine version upgrade

Terraform Configuration Files

resource "aws_rds_cluster" "aurora_postgres" {
  depends_on = [
    aws_rds_cluster_parameter_group.aurora_postgres_db,
    aws_db_parameter_group.aurora_instance_parameter_group
  ]
  cluster_identifier              = "test-aurora-upgrade-cluster"
  engine                          = "aurora-postgresql"
  engine_version                  = 14.3
  port                            = 6160
  database_name                   = "test"
  allow_major_version_upgrade     = true
  db_cluster_parameter_group_name = aws_rds_cluster_parameter_group.aurora_postgres_db.id
  db_instance_parameter_group_name =aws_db_parameter_group.aurora_instance_parameter_group.id
  apply_immediately          = true
}

Steps to Reproduce

• Create an rds aurora postgres cluster with one writer instance - engine version 13.7 and custom cluster and instance parameter groups. Set apply_immediately to true
• Once cluster and instance is created change the engine version to 14.3 also change the parameter groups for cluster and instance to family 14
• Make a deliberate mistake so plan completes but apply fails (i had set apply_immediately to false). Plan succeeds but apply will fail
• Revert apply_immediately to true and run apply again. Will get the below error:
  Error: updating RDS Cluster: InvalidParameterCombination: The current DB instance parameter group is custom. You must explicitly specify a new DB instance parameter group, either default or custom, for the engine version upgrade

Debug Output

No response

Panic Output

No response

Important Factoids

No response

References

No response

Would you like to implement a fix?

No

[github-actions]

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[github-actions]

This functionality has been released in v4.62.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
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