Bug when passing EC2 instance from module to CloudWatch metric module

[ghost]

This issue was originally opened by @hbashary as hashicorp/terraform#24637. It was migrated here as a result of the provider split. The original body of the issue is below.

---

Terraform Version

Terraform v0.12.13

Terraform Configuration Files

module "seg-01-ec2-instance" {
  source                 = "../../modules/ec2"
  segment                = "test1"
  subnet_tag_name        = "*1a-private*"
  kms_alias              = "alias/sf-shoppers-test-us-east-1-master-kmskey"
  ec2_service_role       = "${var.ec2-instance-config["ec2_service_role"]}"
  ami                    = "${var.ec2-instance-config["ami"]}"
  instance_type          = "${var.ec2-instance-config["instance_type"]}"
  key_name               = "${var.ec2-instance-config["key_name"]}"
  security_groups        = concat("${data.aws_security_groups.shop-data-proxy-sg.ids}",
                                  "${data.aws_security_groups.shop-data-ec2-sg.ids}")
  vpc_security_group_ids = "${data.aws_security_groups.shop-data-base-sg.ids}"
  volume_size            = "${var.root-block-device-config["volume_size"]}"
  volume_type            = "${var.root-block-device-config["volume_type"]}"
  user_data              = "${file("user-data.sh")}"

  tags = {
    Name               = "${var.tags-config["Name"]}"
    owner              = "${var.tags-config["owner"]}"
    contact            = "${var.tags-config["contact"]}"
    cost-center        = "${var.tags-config["cost-center"]}"
    off-hours-shutdown = "${var.tags-config["off-hours-shutdown"]}"
    region             = "${var.tags-config["region"]}"
    ou                 = "${var.tags-config["ou"]}"
    env                = "${var.tags-config["env"]}"
    deployment         = "${var.tags-config["deployment"]}"
  }
}

module "seg-01-ec2-sns-alarms" {
    source              = "../../modules/sns-alarms"
    topic_name          = "${var.ec2-alarm-config["topic_name"]}"
    alarm_cnt           = "${var.ec2-alarm-config["alarm_cnt"]}"
    alarm_name          = "${var.ec2-alarm-config["alarm_name"]}"
    comparison_operator = "${var.ec2-alarm-config["comparison_operator"]}"
    evaluation_periods  = "${var.ec2-alarm-config["evaluation_periods"]}"
    metric_name         = "${var.ec2-alarm-config["metric_name"]}"
    namespace           = "${var.ec2-alarm-config["namespace"]}"
    period              = "${var.ec2-alarm-config["period"]}"
    statistic           = "${var.ec2-alarm-config["statistic"]}"
    unit                = "${var.ec2-alarm-config["unit"]}"
    threshold           = "${var.ec2-alarm-config["threshold"]}"
    alarm_description   = "${var.ec2-alarm-config["alarm_description"]}"

    dimensions          = {
      InstanceId = "${module.seg-01-ec2-instance[0].id}"
    }
}

# ------- EC2 Module 
# -------------------------------------------------------
# Resource      : "aws_instance" "shop-res-instance"
# Description   : Provision EC2 Instance
# -------------------------------------------------------
resource "aws_instance" "shop-res-instance" {
  count = "${length(data.aws_subnet_ids.shop-data-subnets.ids)}"

  ami                    = "${var.ami}"
  instance_type          = "${var.instance_type}"
  subnet_id              = "${element(tolist(data.aws_subnet_ids.shop-data-subnets.ids), count.index)}"
  iam_instance_profile   = "${data.aws_iam_role.shop-ec2-service-role.name}"
  key_name               = "${var.key_name}"
  security_groups        = "${var.security_groups}"
  vpc_security_group_ids = "${var.vpc_security_group_ids}"

  root_block_device {
    delete_on_termination = true
    encrypted             = true
    kms_key_id            = data.aws_kms_alias.shop-data-kms.arn
    volume_size           = "${var.volume_size}"
    volume_type           = "${var.volume_type}"
  }

  user_data              = "${var.user_data}"
  tags                   = "${var.tags}"
}

# Output EC2 instance id
output "id" {
  description = "Output EC2 instance id"
  value       = "${aws_instance.shop-res-instance[*].id}"
}

# Output EC2 private ip
output "private_ip" {
  description = "Output EC2 private ip"
  value       = "${aws_instance.shop-res-instance[*].private_ip}"
}


# -------CloudWatch Module
# Data source to get sns topic arn
data "aws_sns_topic" "shop-data-sns-topic" {
  name = "${var.topic_name}"
}

# ----------------------------------------------------------------------------------
# Resource      : "aws_cloudwatch_metric_alarm" "shop-res-cloudwatch-metric-alarm"
# Description   : Create Cloudwatch metric alarms
# ----------------------------------------------------------------------------------
resource "aws_cloudwatch_metric_alarm" "shop-res-cloudwatch-metric-alarm" {
  count                     = "${var.alarm_cnt}"

  alarm_name                = "${element(var.alarm_name, count.index)}"
  comparison_operator       = "${element(var.comparison_operator, count.index)}"
  evaluation_periods        = "${element(var.evaluation_periods, count.index)}"
  metric_name               = "${element(var.metric_name, count.index)}"
  namespace                 = "${var.namespace}"
  period                    = "${element(var.period, count.index)}"
  statistic                 = "${element(var.statistic, count.index)}"
  unit                      = "${element(var.unit, count.index)}"
  threshold                 = "${element(var.threshold, count.index)}"
  alarm_description         = "${element(var.alarm_description, count.index)}"
  alarm_actions             = [ "${data.aws_sns_topic.shop-data-sns-topic.arn}" ]

  dimensions                = "${var.dimensions}"
}

Debug Output

module.seg-01-ebs-volumes.aws_ebs_volume.shop-res-ebs-volume[0]: Creating...
module.seg-01-ebs-volumes.aws_ebs_volume.shop-res-ebs-volume[1]: Creating...
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Creating...
module.seg-01-ec2-instance.aws_instance.shop-res-instance[0]: Creating...
module.seg-01-ebs-volumes.aws_ebs_volume.shop-res-ebs-volume[0]: Still creating... [10s elapsed]
module.seg-01-ebs-volumes.aws_ebs_volume.shop-res-ebs-volume[1]: Still creating... [10s elapsed]
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [10s elapsed]
module.seg-01-ec2-instance.aws_instance.shop-res-instance[0]: Still creating... [10s elapsed]
module.seg-01-ebs-volumes.aws_ebs_volume.shop-res-ebs-volume[1]: Creation complete after 13s [id=vol-0d94d462564708003]
module.seg-01-ebs-volumes.aws_ebs_volume.shop-res-ebs-volume[0]: Creation complete after 13s [id=vol-080ca25d31a2b2969]
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [20s elapsed]
module.seg-01-ec2-instance.aws_instance.shop-res-instance[0]: Still creating... [20s elapsed]
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [30s elapsed]
module.seg-01-ec2-instance.aws_instance.shop-res-instance[0]: Still creating... [30s elapsed]
module.seg-01-ec2-instance.aws_instance.shop-res-instance[0]: Creation complete after 31s [id=i-04304990a50a35c25]
module.seg-01-ebs-volumes.aws_volume_attachment.shop-res-ebs-attach[1]: Creating...
module.seg-01-ebs-volumes.aws_volume_attachment.shop-res-ebs-attach[0]: Creating...
module.seg-01-ec2-instance-record-set.aws_route53_record.shop-res-route53-record: Creating...
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [40s elapsed]
module.seg-01-ebs-volumes.aws_volume_attachment.shop-res-ebs-attach[1]: Still creating... [10s elapsed]
module.seg-01-ebs-volumes.aws_volume_attachment.shop-res-ebs-attach[0]: Still creating... [10s elapsed]
module.seg-01-ec2-instance-record-set.aws_route53_record.shop-res-route53-record: Still creating... [10s elapsed]
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [50s elapsed]
module.seg-01-ebs-volumes.aws_volume_attachment.shop-res-ebs-attach[1]: Still creating... [20s elapsed]
module.seg-01-ec2-instance-record-set.aws_route53_record.shop-res-route53-record: Still creating... [20s elapsed]
module.seg-01-ebs-volumes.aws_volume_attachment.shop-res-ebs-attach[0]: Still creating... [20s elapsed]
module.seg-01-ebs-volumes.aws_volume_attachment.shop-res-ebs-attach[0]: Creation complete after 24s [id=vai-1117887475]
module.seg-01-ebs-volumes.aws_volume_attachment.shop-res-ebs-attach[1]: Creation complete after 24s [id=vai-313197564]
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [1m0s elapsed]
module.seg-01-ec2-instance-record-set.aws_route53_record.shop-res-route53-record: Still creating... [30s elapsed]
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [1m10s elapsed]
module.seg-01-ec2-instance-record-set.aws_route53_record.shop-res-route53-record: Still creating... [40s elapsed]
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [1m20s elapsed]
module.seg-01-ec2-instance-record-set.aws_route53_record.shop-res-route53-record: Still creating... [50s elapsed]
module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0]: Still creating... [1m30s elapsed]
module.seg-01-ec2-instance-record-set.aws_route53_record.shop-res-route53-record: Still creating... [1m0s elapsed]
module.seg-01-ec2-instance-record-set.aws_route53_record.shop-res-route53-record: Creation complete after 1m8s [id=Z04286331F61LJQQ4X1W4_discovery.shoppers.test.ic1.statefarm._A]

Error: configuration for module.seg-01-ec2-sns-alarms.aws_cloudwatch_metric_alarm.shop-res-cloudwatch-metric-alarm[0] still contains unknown values during apply (this is a bug in Terraform; please report it!)

Crash Output

Expected Behavior

A CloudWatch alert should have been created.

Actual Behavior

EC2 instance gets created but no Cloudwatch alert.

Steps to Reproduce

1. terraform init
2. terraform apply

Additional Context

References

[justinretzolk]

Hey @hbashary 👋 Thank you for taking the time to file this. Given that there's been a number of AWS Provider releases since you initially filed it, can you confirm if you're still experiencing this behavior?