Only set monitoring_role_arn if monitoring_interval > 0

[rbreslow]

Overview

• Update main.tf
• Add note about enhanced monitoring support to README.md

Fixes #31

Connects hashicorp/terraform-provider-aws#5559
Connects hashicorp/terraform-provider-aws#2188
Connects hashicorp/terraform-provider-aws#315

See: hashicorp/terraform-provider-aws#315 (comment)

Testing Instructions

I setup a local Terraform project and pointed the AWS backend to our R&D account.

Next, I created an instance of this module with a monitoring interval of 0:

module "database" {
  source = "github.com/azavea/terraform-aws-postgresql-rds?ref=d1706c3"

  vpc_id                     = "${module.vpc.id}"
  allocated_storage          = "${var.rds_allocated_storage}"
  engine_version             = "${var.rds_engine_version}"
  instance_type              = "${var.rds_instance_type}"
  storage_type               = "${var.rds_storage_type}"
  database_identifier        = "${var.rds_database_identifier}"
  database_name              = "${var.rds_database_name}"
  database_username          = "${var.rds_database_username}"
  database_password          = "${var.rds_database_password}"
  backup_retention_period    = "${var.rds_backup_retention_period}"
  backup_window              = "${var.rds_backup_window}"
  maintenance_window         = "${var.rds_maintenance_window}"
  auto_minor_version_upgrade = "${var.rds_auto_minor_version_upgrade}"
  final_snapshot_identifier  = "${var.rds_final_snapshot_identifier}"
  skip_final_snapshot        = "${var.rds_skip_final_snapshot}"
  copy_tags_to_snapshot      = "${var.rds_copy_tags_to_snapshot}"
  multi_availability_zone    = "${var.rds_multi_az}"
  storage_encrypted          = "${var.rds_storage_encrypted}"
  subnet_group               = "${aws_db_subnet_group.default.name}"
  parameter_group            = "${aws_db_parameter_group.default.name}"
  monitoring_interval        = "0"

  alarm_cpu_threshold                = "${var.rds_cpu_threshold_percent}"
  alarm_disk_queue_threshold         = "${var.rds_disk_queue_threshold}"
  alarm_free_disk_threshold          = "${var.rds_free_disk_threshold_bytes}"
  alarm_free_memory_threshold        = "${var.rds_free_memory_threshold_bytes}"
  alarm_cpu_credit_balance_threshold = "${var.rds_cpu_credit_balance_threshold}"
  alarm_actions                      = ["${aws_sns_topic.global.arn}"]
  ok_actions                         = ["${aws_sns_topic.global.arn}"]
  insufficient_data_actions          = ["${aws_sns_topic.global.arn}"]

  project     = "${var.project}"
  environment = "${var.environment}"
}

I confirmed in the AWS Console that the RDS instance came online with support for enhanced monitoring disabled.

I changed this value to 60, and cycled Terraform again:

...
An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
  ~ update in-place

Terraform will perform the following actions:

  ~ module.database.aws_db_instance.postgresql
      monitoring_interval: "0" => "60"
      monitoring_role_arn: "" => "arn:aws:iam::279682201306:role/rdsStagingEnhancedMonitoringRole"


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

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

module.database.aws_db_instance.postgresql: Modifying... (ID: rockytesting)
  monitoring_interval: "0" => "60"
  monitoring_role_arn: "" => "arn:aws:iam::279682201306:role/rdsStagingEnhancedMonitoringRole"
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 10s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 20s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 30s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 40s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 50s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 1m0s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 1m10s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 1m20s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 1m30s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 1m40s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 1m50s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 2m0s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 2m10s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 2m20s elapsed)
module.database.aws_db_instance.postgresql: Still modifying... (ID: rockytesting, 2m30s elapsed)
module.database.aws_db_instance.postgresql: Modifications complete after 2m33s (ID: rockytesting)

Apply complete! Resources: 0 added, 1 changed, 0 destroyed.

I confirmed in the AWS Console that the RDS instance came online with support for enhanced monitoring enabled.

[hectcastro]

Nice concise fix. 👍