[Bug] aws_cloudwatch_metric_alarm metric period differs from AWS API spec

[pureiboi]

Terraform and AWS Provider Version

`Terraform v1.11.4`
`hashicorp/aws v5.94.1`

Affected Resource(s) or Data Source(s)

• aws_cloudwatch_metric_alarm

Expected Behavior

Period = 20 is supported, and able to apply without error

Actual Behavior

Error flagged on unsupported value

Relevant Error/Panic Output

Example 1
aws_cloudwatch_metric_alarm

│ Error: expected period to be one of [10 30], got 20
│ 
│   with aws_cloudwatch_metric_alarm.example1,
│   on main.tf line 88, in resource "aws_cloudwatch_metric_alarm" "example1":
│   88:   period = local.period
│ 
╵
╷
│ Error: expected period to be divisible by 60, got: 20
│ 
│   with aws_cloudwatch_metric_alarm.example1,
│   on main.tf line 88, in resource "aws_cloudwatch_metric_alarm" "example1":
│   88:   period = local.period
│ 
╵

Example 2
aws_cloudwatch_metric_alarm -> metric_query

│ Error: expected metric_query.0.period to be one of [1 5 10 30], got 20
│ 
│   with aws_cloudwatch_metric_alarm.example2,
│   on main.tf line 98, in resource "aws_cloudwatch_metric_alarm" "example2":
│   98: resource "aws_cloudwatch_metric_alarm" "example2" {
│ 
╵
╷
│ Error: expected metric_query.0.period to be divisible by 60, got: 20
│ 
│   with aws_cloudwatch_metric_alarm.example2,
│   on main.tf line 98, in resource "aws_cloudwatch_metric_alarm" "example2":
│   98: resource "aws_cloudwatch_metric_alarm" "example2" {
│ 
╵

Example 3
aws_cloudwatch_metric_alarm -> metric_query -> metric

Planning failed. OpenTofu encountered an error while generating this plan.

╷
│ Error: expected metric_query.0.metric.0.period to be one of [1 5 10 30], got 20
│ 
│   with aws_cloudwatch_metric_alarm.example3["ui-jobseekersupport"],
│   on main.tf line 117, in resource "aws_cloudwatch_metric_alarm" "example3":
│  117: resource "aws_cloudwatch_metric_alarm" "example3" {
│ 
╵
╷
│ Error: expected metric_query.0.metric.0.period to be divisible by 60, got: 20
│ 
│   with aws_cloudwatch_metric_alarm.example3["ui-jobseekersupport"],
│   on main.tf line 117, in resource "aws_cloudwatch_metric_alarm" "example3":
│  117: resource "aws_cloudwatch_metric_alarm" "example3" {
│ 
╵

Sample Terraform Configuration

Click to expand configuration

locals {
  period = 20
}


resource "aws_cloudwatch_metric_alarm" "example1" {
  for_each                  = var.endpoint_health_checks 
  alarm_description         = "alarm for ${each.key} on healthcheck ID ${aws_route53_health_check.endpoint[each.key].id}"
  alarm_name                = "route53_alarm_${each.key}"
  comparison_operator       = "LessThanOrEqualToThreshold"
  datapoints_to_alarm       = 1
  evaluation_periods        = 2
  metric_name               = "HealthCheckPercentageHealthy"
  namespace                 = "AWS/Route53"
  period = local.period
  statistic                 = "Average"
  dimensions = {
    HealthCheckId = aws_route53_health_check.endpoint[each.key].id
  }
  provider = aws.us-east-1
}



resource "aws_cloudwatch_metric_alarm" "example2" {
  for_each                  = var.endpoint_health_checks 
  alarm_description         = "alarm for ${each.key} on healthcheck ID ${aws_route53_health_check.endpoint[each.key].id}"
  alarm_name                = "route53_alarm_${each.key}"
  evaluation_periods = 2
  datapoints_to_alarm = 1
  comparison_operator       = "LessThanOrEqualToThreshold"
  provider = aws.us-east-1
  metric_query {
    id          = "e1"
    period = local.period
    return_data = "false"
  }
}


resource "aws_cloudwatch_metric_alarm" "example3" {
  for_each                  = var.endpoint_health_checks 
  alarm_description         = "alarm for ${each.key} on healthcheck ID ${aws_route53_health_check.endpoint[each.key].id}"
  alarm_name                = "route53_alarm_${each.key}"
  comparison_operator       = "LessThanOrEqualToThreshold"
  evaluation_periods = 2
  datapoints_to_alarm = 1
  provider = aws.us-east-1

  metric_query {
    id          = "e1"
    metric {
      period = local.period
      stat = "Average"
      metric_name = "HealthCheckPercentageHealthy"
      namespace = "AWS/Route53"
      dimensions = {
        HealthCheckId = aws_route53_health_check.endpoint[each.key].id
      }
    }
    return_data = "false"
  }
}

Steps to Reproduce

1. apply configuration with period = 20

Debug Logging

GenAI / LLM Assisted Development

n/a

Important Facts and References

As per AWS API doc for PutMetricAlarm https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_PutMetricAlarm.html

API PutMetricAlarm, Period can support 10, 20, 30, and any multiple of 60.

As per AWS API doc MetricDataQuery https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_MetricDataQuery.html

API MetricDataQuery, Period can support 1, 5, 10, 20, 30, 60, or any multiple of 60

Would you like to implement a fix?

Yes

[github-actions]

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[github-actions]

This functionality has been released in v5.98.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

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