fix: default to AWS provided option and parameter groups when not creating nor providing

[bryantbiggs]

Description

• default to AWS provided option and parameter groups when not creating nor providing

Motivation and Context

• with fix: update option group to fix name vs. name_prefix and conditional creation for postgresql #302 and fix: update parameter group to fix name vs. name_prefix #304 changes to fix naming conventions used, it introduced an error where users were relying on the default behavior provided by the Terraform AWS provider and/or AWS where a default option/parameter group would be used if one is not provided. this is intended to correct that while preserving the changes to the naming schemes

Closes #303
Closes #305
Cloess #307

Breaking Changes

• No

How Has This Been Tested?

• I have tested and validated these changes using one or more of the provided examples/* projects
• Validated using examples/complete-mysql and examples/complete-postgresql + added 2nd set of configs to both to prove this case here where a default group will be used by AWS when none is provided

[codezninja]

I did a plan with my local project and confirmed that it works as I expected before this latest release.

[bryantbiggs]

thanks @bondezbond !

[apjneeraj]

@bryantbiggs: It looks like similar change is required for db_subnet_group_name as function coalesce fails with same error due to 'module.db_subnet_group.this_db_subnet_group_id' parameter which does not has a value yet in case I try to create db_subnet_group.

[bryantbiggs]

good point, the subnet changes were coming down the pipe as well till this little snafu (master...bryantbiggs:fix/subnet-group) - I can put this back to the original though for the time being in this PR

[bryantbiggs]

updated in c66fc9c

[sayertindall]

I just cloned your fork and attempted to run the complete_postgresql example and it's still throwing the same error:
super new to Terraform, so this could totally be an error on my end.

  on ../../modules/db_parameter_group/main.tf line 12, in resource "aws_db_parameter_group" "this":
  12:   name_prefix = local.name_prefix```

[bryantbiggs]

ya I'm not sure @sayerrrr what the error might be, I spun up both the complete-mysql and complete-postgresql as they are defined in this PR and no issue

[sayertindall]

@bryantbiggs interesting, let me see what i can come up with - appreciate your time!

[siozosdr]

Will this fix also include the use-case of using the module to setup an RDS replica?

The error I'm currently getting is related to the mentioned issues #303 #305 #307:

Error: Error in function call

  on .terraform/modules/dis_replica/main.tf line 3, in locals:
   3:   db_subnet_group_name   = coalesce(var.db_subnet_group_name, module.db_subnet_group.this_db_subnet_group_id)
    |----------------
    | module.db_subnet_group.this_db_subnet_group_id is ""
    | var.db_subnet_group_name is ""

Call to function "coalesce" failed: no non-null, non-empty-string arguments.


Error: Error in function call

  on .terraform/modules/dis_replica/main.tf line 5, in locals:
   5:   parameter_group_name_id = coalesce(var.parameter_group_name, module.db_parameter_group.this_db_parameter_group_id)
    |----------------
    | module.db_parameter_group.this_db_parameter_group_id is ""
    | var.parameter_group_name is ""

Call to function "coalesce" failed: no non-null, non-empty-string arguments.


Error: first character of parameter group "name_prefix" must be a letter

  on .terraform/modules/dis_primary/modules/db_parameter_group/main.tf line 12, in resource "aws_db_parameter_group" "this":
  12:   name_prefix = local.name_prefix

I'm setting up a replica using the following options in my module:

module "dis_replica" {
  source  = "terraform-aws-modules/rds/aws"
  version = "2.25.0"

  identifier = "${local.dis_master_db_identifier}-replica1"

  apply_immediately = true

  auto_minor_version_upgrade = false

  # Source database. For cross-region use this_db_instance_arn
  replicate_source_db = module.dis_primary.this_db_instance_id

  engine                = local.dis_engine
  engine_version        = local.dis_engine_version
  instance_class        = local.dis_instance_class
  allocated_storage     = local.dis_allocated_storage
  max_allocated_storage = local.dis_max_allocated_storage
  storage_type          = local.dis_storage_type
  storage_encrypted     = local.dis_storage_encrypted
  port                  = local.dis_port

  # Username and password must not be set for replicas
  username = ""
  password = ""

  vpc_security_group_ids = [module.vpc.default_security_group_id, aws_security_group.dis_rds.id]

  maintenance_window = local.dis_maintenance_window
  backup_window      = local.dis_backup_window

  performance_insights_enabled          = local.dis_performance_insights_enabled
  performance_insights_retention_period = local.dis_performance_insights_retention_period

  deletion_protection = true
  # disable backups to create DB faster
  backup_retention_period = 0

  # Not allowed to specify a subnet group for replicas in the same region
  create_db_subnet_group = false

  create_db_option_group    = false
  create_db_parameter_group = false
}

[bryantbiggs]

@siozosdr yes

[antonbabenko]

@bryantbiggs Please let me know when you think it is ready to be merged.

[bryantbiggs]

we should be all set @antonbabenko - did one last check using complete-mysql and everything still looks good

[antonbabenko]

Let's see! 🤞

v2.26.0 has been just released.

[github-actions]

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