aws_cdk.aws_cloudwatch: CfnAlarm drops MetricDataQueryProperty contents if arguments come from a dict

[SC-CTS]

Describe the bug

When instantiatig a CfnAlarm from a Dict as follows:

CfnAlarm(scope=self, id="cfn-alarm", **{
    'alarm_name': 'Descriptive Name', 
    'alarm_description': 'Very descriptive description.', 
    'actions_enabled': True, 
    'ok_actions': ['arn:aws:sns:eu-central-1:666:XXX_CloudWatch_Integration'], 
    'alarm_actions': ['arn:aws:sns:eu-central-1:666:XXX_CloudWatch_Integration'], 
    'insufficient_data_actions': [], 
    'evaluation_periods': 15, 
    'datapoints_to_alarm': 15, 
    'threshold': 1.5, 
    'comparison_operator': 'LessThanThreshold', 
    'treat_missing_data': 'missing', 
    'metrics': [
      {
        'id': 'e1', 
        'label': 'Currently running Alerts', 
        'return_data': True, 
        'expression': 'MAX(METRICS()/3)'
      }, 
      {
        'id': 'm1', 
        'return_data': False, 
        'metric_stat': {
          'metric': {
            'namespace': 'project', 
            'metric_name': 'gauge.project.value', 
            'dimensions': []
          }, 
          'period': 60, 
          'stat': 'Average'
        }
      }
    ]
  })

It will fail with the following error from the Stack: Resource handler returned message: "Period must not be null (Service: CloudWatch, Status Code: 400, Request ID: 123)"

Expected Behavior

The Alarm should be created successfully and the stack should not fail.

Current Behavior

When checking the synth output in cdk.out I see the following was generated:

{
  "abcde": {
    "Type": "AWS::CloudWatch::Alarm",
    "Properties": {
      "ActionsEnabled": true,
      "AlarmActions": [
        "arn:aws:sns:eu-central-1:666:XXX_CloudWatch_Integration"
      ],
      "AlarmDescription": "Very descriptive description.",
      "AlarmName": "Descriptive Name",
      "ComparisonOperator": "LessThanThreshold",
      "DatapointsToAlarm": 15,
      "EvaluationPeriods": 15,
      "InsufficientDataActions": [],
      "Metrics": [
        {
          "Expression": "MAX(METRICS()/3)",
          "Id": "e1",
          "Label": "Currently running Alerts"
        },
        {
          "Id": "m1"
        }
      ],
      "OKActions": [
        "arn:aws:sns:eu-central-1:666:XXX_CloudWatch_Integration"
      ],
      "Threshold": 1.5,
      "TreatMissingData": "missing"
    },
    "DependsOn": [
      "qwer",
      "zxc"
    ],
    "Metadata": {
      "aws:cdk:path": "hjk"
    }
  }
}

The second object in abcde.Properties.Metrics with "id": "m1" is missing all properties.

Reproduction Steps

See provided code.

Possible Solution

Instantiating the MetricDataQueryProperty manually like so:

CfnAlarm(scope=self, id="cfn-alarm", **{
    'alarm_name': 'Descriptive Name', 
    'alarm_description': 'Very descriptive description.', 
    'actions_enabled': True, 
    'ok_actions': ['arn:aws:sns:eu-central-1:666:XXX_CloudWatch_Integration'], 
    'alarm_actions': ['arn:aws:sns:eu-central-1:666:XXX_CloudWatch_Integration'], 
    'insufficient_data_actions': [], 
    'evaluation_periods': 15, 
    'datapoints_to_alarm': 15, 
    'threshold': 1.5, 
    'comparison_operator': 'LessThanThreshold', 
    'treat_missing_data': 'missing', 
    'metrics': [
      CfnAlarm.MetricDataQueryProperty(**{
        'id': 'e1', 
        'label': 'Currently running Alerts', 
        'return_data': True, 
        'expression': 'MAX(METRICS()/3)'
      }), 
      CfnAlarm.MetricDataQueryProperty(**{
        'id': 'm1', 
        'return_data': False, 
        'metric_stat': {
          'metric': {
            'namespace': 'project', 
            'metric_name': 'gauge.project.value', 
            'dimensions': []
          }, 
          'period': 60, 
          'stat': 'Average'
        }
      })
    ]
  })

Will generate the expected, correct CF code in cdk.out. This is not great because we load the CF from a file and would like to not parse it any further if possible.

Additional Information/Context

When checking the CfnAlarmProps spec: https://docs.aws.amazon.com/cdk/api/v2/python/aws_cdk.aws_cloudwatch/CfnAlarmProps.html
I would interpret the type for metrics (Union[IResolvable, Sequence[Union[IResolvable, MetricDataQueryProperty, Dict[str, Any]]], None]) to allow for Dicts. Maybe I just misinterpeted that?

CDK CLI Version

2.99.1 (build b2a895e)

Framework Version

No response

Node.js Version

18.16.0

OS

Ubuntu 20.04.6 LTS (in WSL on Win 11)

Language

Python

Language Version

Python 3.11

Other information

No response

[khushail]

Hi @SC-CTS ,thanks for reaching out.

Going through the available documentation about Metrics, it expects the array objects to be of type CfnAlarm.MetricDataQueryProperty as given in this example.. So when you explicitly added this and corrected the code, it produced the correct CF template.

And you also mentioned about using CF from file, so using Cloudformation Include module might help solve your usecase. Let me know if it does not help.

[github-actions]

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