[Bug]: Cloudwatch Metric Alarm 'metric_query' block does not Support Period in Conjunction With Expression

[jhwbarlow]

Terraform Core Version

1.3.6

AWS Provider Version

4.48.0

Affected Resource(s)

• aws_cloudwatch_metric_alarm

Expected Behavior

When creating a Metric Alarm that uses an expression, it is not possible to set the period. However, this is a valid configuration in CloudWatch and can be successfuly performed via the web console and the API.

Actual Behavior

This leads to the request being rejected by AWS as the 'period' field is missing in the request.

Relevant Error/Panic Output Snippet

Error: Updating metric alarm failed: ValidationError: Period must not be null
│       status code: 400, request id: 95fc8690-15f5-433d-85f1-3a34e6516db8
│ 
│   with module.redshift_cluster.aws_cloudwatch_metric_alarm.wlm_total_average_queue_length[0],
│   on ../../../modules/redshift_cluster/main.tf line 378, in resource "aws_cloudwatch_metric_alarm" "wlm_total_average_queue_length":
│  378: resource "aws_cloudwatch_metric_alarm" "wlm_total_average_queue_length" {

Terraform Configuration Files

resource "aws_cloudwatch_metric_alarm" "wlm_total_average_queue_length" {
  alarm_name          = "redshift-archive-wlm-total-avg-queue-length"
  comparison_operator = "GreaterThanOrEqualToThreshold"
  evaluation_periods  = 1
  datapoints_to_alarm = 1
  threshold           = 5
  alarm_description   = "The WLM queue length across all queues has exceeded 5 on average in the last 15 minutes"
  
  metric_query {   
    id          = "avg_queue_length_all_queues"
    expression  = "SELECT AVG(WLMQueueLength) FROM \"AWS/Redshift\" WHERE ClusterIdentifier = 'archive'" # No QueueName dimension as we want to get the avg of all queue lengths
    label       = "Average queue length across all WLM queues"
    return_data = true
    // period      = 15 * 60 # Unable to set in TF
  }

  alarm_actions = ["arn:aws:sns:eu-west-1:582261275102:NotifyMe"]
}

Steps to Reproduce

• Attempt to create a Cloudwatch Alarm with an expression

Debug Output

No response

Panic Output

No response

Important Factoids

No response

References

An example in Python showing the successful creation of such a metric:

import boto3

def create_alarm(
    sns_topic_arn: str,
    redshift_cluster_identifier: str,
    evaluation_period_minutes: int=15,
    wlm_queue_total_average_max_acceptable_length: int=5
) -> None:
    cloudwatch = boto3.client('cloudwatch')

    alarm_data = {
        "AlarmName": f"redshift-{redshift_cluster_identifier}-wlm-total-avg-queue-length",
        "AlarmDescription": f"The WLM queue length across all queues has exceeded {wlm_queue_total_average_max_acceptable_length} on average in the last {evaluation_period_minutes} minutes",
        "ActionsEnabled": True,
        "AlarmActions": [sns_topic_arn],
        "EvaluationPeriods": 1,
        "DatapointsToAlarm": 1,
        "Threshold": wlm_queue_total_average_max_acceptable_length,
        "ComparisonOperator": "GreaterThanOrEqualToThreshold",
        "TreatMissingData": "missing",
        "Metrics": [
            {
                "Id": "avg_queue_length_all_queues",
                "Expression": f"SELECT AVG(WLMQueueLength) FROM \"AWS/Redshift\" WHERE ClusterIdentifier = '{redshift_cluster_identifier}'",
                "Label": "Average queue length across all WLM queues",
                "ReturnData": True,
                "Period": evaluation_period_minutes * 60
            }
        ]
    }

    cloudwatch.put_metric_alarm(**alarm_data)

REDSHIFT_CLUSTER_IDENTIFIER = "archive"
SNS_TOPIC_ARN = "arn:aws:sns:eu-west-1:582261275102:NotifyMe"

if __name__ == "__main__":
    create_alarm(sns_topic_arn=SNS_TOPIC_ARN, redshift_cluster_identifier=REDSHIFT_CLUSTER_IDENTIFIER)

Would you like to implement a fix?

None

[github-actions]

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[jhwbarlow]

Just seen this PR which looks like it may do the job here.

[github-actions]

This functionality has been released in v4.59.0 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.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.