CloudWatch: Math expression in alarm doesn't respect period

[hakenmt]

Describe the bug

I'm defining an alarm as follows:

let latencyImpactAlarm: Alarm = new Alarm(
        this,
        val + "LatencyImpact",
        {
          alarmName: val + "-node-high-latency-impact",
          actionsEnabled: false,
          datapointsToAlarm: 3,
          evaluationPeriods: 5,
          metric: new MathExpression({
            period: Duration.seconds(60),
            expression: 'TIME_SERIES(0) + ((INSIGHT_RULE_METRIC("' +
              latencyRule.ruleName +
              '", "MaxContributorValue") / m1) * 100)',
            usingMetrics: {
              "m1": new Metric({
                namespace: "AWS/ApplicationELB",
                metricName: "RequestCount",
                dimensionsMap: {
                  "LoadBalancer": value
                },
                statistic: "Sum",
                period: Duration.seconds(60)
              })
            }
          }),
          threshold: .1,
          comparisonOperator:
            ComparisonOperator.GREATER_THAN_OR_EQUAL_TO_THRESHOLD,
        },
      );

This produces CFN as follows:

"Metrics": [
     {
      "Expression": "TIME_SERIES(0) + ((INSIGHT_RULE_METRIC(\"HighLatencyRequestsPerNode-app-multi--ALBAE-7sFFT5bABDxM-2fa0f6aeb46f1279\", \"MaxContributorValue\") / m1) * 100)",
      "Id": "expr_1"
     },
     {
      "Id": "m1",
      "MetricStat": {
       "Metric": {
        "Dimensions": [
         {
          "Name": "LoadBalancer",
          "Value": "app/multi--ALBAE-7sFFT5bABDxM/2fa0f6aeb46f1279"
         }
        ],
        "MetricName": "RequestCount",
        "Namespace": "AWS/ApplicationELB"
       },
       "Period": 60,
       "Stat": "Sum"
      },
      "ReturnData": false
     }
    ],

When deployed, this causes an error: Resource handler returned message: "Error in expression 'expr_1': Parameter Query Period is invalid. Please specify a Period.

Even though the period is set, it is not included in the synth'd CFN template. If you add in the period manually, the resource successfully deploys.

{
      "Expression": "TIME_SERIES(0) + ((INSIGHT_RULE_METRIC(\"HighLatencyRequestsPerNode-app-multi--ALBAE-7sFFT5bABDxM-2fa0f6aeb46f1279\", \"MaxContributorValue\") / m1) * 100)",
      "Id": "expr_1",
      "Period": 60
     },

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Version

No response

Expected Behavior

I expect the period field to be included in the resulting CFN.

Current Behavior

It does not.

Reproduction Steps

Provided above.

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.138.0

Framework Version

No response

Node.js Version

20

OS

darwin

Language

TypeScript

Language Version

No response

Other information

No response

[ashishdhingra]

Reproducible using below customer provided code:

import * as cdk from 'aws-cdk-lib';
import * as cloudwatch from 'aws-cdk-lib/aws-cloudwatch';

export class CdktestStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const alarm = new cloudwatch.Alarm(this, 'MyAlarm', {
      alarmName: 'TestAlarm',
      actionsEnabled: false,
      datapointsToAlarm: 3,
      evaluationPeriods: 5,
      metric: new cloudwatch.MathExpression({
        period: cdk.Duration.seconds(60),
        expression: 'TIME_SERIES(0) + ((INSIGHT_RULE_METRIC("' +
              'testrulename' +
              '", "MaxContributorValue") / m1) * 100)',
        usingMetrics: {
          "m1": new cloudwatch.Metric({
            namespace: "AWS/ApplicationELB",
                metricName: "RequestCount",
                dimensionsMap: {
                  "LoadBalancer": "test"
                },
                statistic: "Sum",
                period: cdk.Duration.seconds(60)
          })
        }
      }),
      threshold: 1,
      comparisonOperator: cloudwatch.ComparisonOperator.GREATER_THAN_OR_EQUAL_TO_THRESHOLD
    });
  }
}

Running cdk synth works fine and generates the below CloudFormation template:

Resources:
  MyAlarm696658B6:
    Type: AWS::CloudWatch::Alarm
    Properties:
      ActionsEnabled: false
      AlarmName: TestAlarm
      ComparisonOperator: GreaterThanOrEqualToThreshold
      DatapointsToAlarm: 3
      EvaluationPeriods: 5
      Metrics:
        - Expression: TIME_SERIES(0) + ((INSIGHT_RULE_METRIC("testrulename", "MaxContributorValue") / m1) * 100)
          Id: expr_1
        - Id: m1
          MetricStat:
            Metric:
              Dimensions:
                - Name: LoadBalancer
                  Value: test
              MetricName: RequestCount
              Namespace: AWS/ApplicationELB
            Period: 60
            Stat: Sum
          ReturnData: false
      Threshold: 1
    Metadata:
      aws:cdk:path: CdktestStack/MyAlarm/Resource
  CDKMetadata:
    Type: AWS::CDK::Metadata
    Properties:
      Analytics: v2:deflate64:H4sIAAAAAAAA/yXGQQ6DIBAAwLd4h60a03Bt+gP7ALNdaEQREhbKwfB3o55meuieCtoGC0vSq3T2C/snIa0CC0/kQtYFE82wvxzGTbx//ko9NxoOOZKpwgdtYOHHv1PQtzA0C1srY/bJbgbG2wMtdOBxbQAAAA==
    Metadata:
      aws:cdk:path: CdktestStack/CDKMetadata/Default
Parameters:
  BootstrapVersion:
    Type: AWS::SSM::Parameter::Value<String>
    Default: /cdk-bootstrap/hnb659fds/version
    Description: Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]

Running cdk deploy gives the below error:

✨  Synthesis time: 3.88s

CdktestStack: start: Building 8a0193553528ae2ff8bc78613dd9272f1ab325842a9536f50ae03bd70f3da6bf:<<ACCOUNT_ID>>-us-east-2
CdktestStack: success: Built 8a0193553528ae2ff8bc78613dd9272f1ab325842a9536f50ae03bd70f3da6bf:<<ACCOUNT_ID>>-us-east-2
CdktestStack: start: Publishing 8a0193553528ae2ff8bc78613dd9272f1ab325842a9536f50ae03bd70f3da6bf:<<ACCOUNT_ID>>-us-east-2
CdktestStack: success: Published 8a0193553528ae2ff8bc78613dd9272f1ab325842a9536f50ae03bd70f3da6bf:<<ACCOUNT_ID>>-us-east-2
CdktestStack: deploying... [1/1]
CdktestStack: creating CloudFormation changeset...
2:08:33 PM | CREATE_FAILED        | AWS::CloudWatch::Alarm | MyAlarm696658B6
Resource handler returned message: "Error in expression 'expr_1': Parameter Query Period is invalid. Please specify a Period. (Service: AmazonCloudWatch; Status Code: 400; Error Code: ValidationException; Request ID: 33fa0563-08e4-4c71-946a-6f18e0
fe19a9; Proxy: null) (Service: CloudWatch, Status Code: 400, Request ID: 33fa0563-08e4-4c71-946a-6f18e0fe19a9)" (RequestToken: d12a4313-3f5d-335d-bad7-d44554d3ccdc, HandlerErrorCode: GeneralServiceException)

❌  CdktestStack failed: Error: The stack named CdktestStack failed creation, it may need to be manually deleted from the AWS console: ROLLBACK_COMPLETE: Resource handler returned message: "Error in expression 'expr_1': Parameter Query Period is invalid. Please specify a Period. (Service: AmazonCloudWatch; Status Code: 400; Error Code: ValidationException; Request ID: 33fa0563-08e4-4c71-946a-6f18e0fe19a9; Proxy: null) (Service: CloudWatch, Status Code: 400, Request ID: 33fa0563-08e4-4c71-946a-6f18e0fe19a9)" (RequestToken: d12a4313-3f5d-335d-bad7-d44554d3ccdc, HandlerErrorCode: GeneralServiceException)

Looks like in PR #7644, it allowed to set Period when using MathExpression without submetrics. So below CDK code:

export class CdktestStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    new cloudwatch.Alarm(this, 'Alarm', {
      alarmName: 'TestAlarm',
      actionsEnabled: false,
      datapointsToAlarm: 3,
      evaluationPeriods: 5,
      metric: new cloudwatch.MathExpression({
        expression: 'INSIGHT_RULE_METRIC("SomeId", UniqueContributors)',
        usingMetrics: {},
        period: cdk.Duration.seconds(60)
      }),
      threshold: 1,
    });
  }
}

synthesizes to below CloudFormation template:

Resources:
  Alarm7103F465:
    Type: AWS::CloudWatch::Alarm
    Properties:
      ActionsEnabled: false
      AlarmName: TestAlarm
      ComparisonOperator: GreaterThanOrEqualToThreshold
      DatapointsToAlarm: 3
      EvaluationPeriods: 5
      Metrics:
        - Expression: INSIGHT_RULE_METRIC("SomeId", UniqueContributors)
          Id: expr_1
          Period: 60
      Threshold: 1
    Metadata:
      aws:cdk:path: CdktestStack/Alarm/Resource
  CDKMetadata:
    Type: AWS::CDK::Metadata
    Properties:
      Analytics: v2:deflate64:H4sIAAAAAAAA/yXGQQ6DIBAAwLd4h60a03Bt+gP7ALNdaEQREhbKwfB3o55meuieCtoGC0vSq3T2C/snIa0CC0/kQtYFE82wvxzGTbx//ko9NxoOOZKpwgdtYOHHv1PQtzA0C1srY/bJbgbG2wMtdOBxbQAAAA==
    Metadata:
      aws:cdk:path: CdktestStack/CDKMetadata/Default
Parameters:
  BootstrapVersion:
    Type: AWS::SSM::Parameter::Value<String>
    Default: /cdk-bootstrap/hnb659fds/version
    Description: Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]

@hakenmt You could try to use raw property override as a workaround (demonstrated below):

import * as cdk from 'aws-cdk-lib';
import * as cloudwatch from 'aws-cdk-lib/aws-cloudwatch';

export class CdktestStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const alarm = new cloudwatch.Alarm(this, 'MyAlarm', {
      alarmName: 'TestAlarm',
      actionsEnabled: false,
      datapointsToAlarm: 3,
      evaluationPeriods: 5,
      metric: new cloudwatch.MathExpression({
        period: cdk.Duration.seconds(60),
        expression: 'TIME_SERIES(0) + ((INSIGHT_RULE_METRIC("' +
              'testrulename' +
              '", "MaxContributorValue") / m1) * 100)',
        usingMetrics: {
          "m1": new cloudwatch.Metric({
            namespace: "AWS/ApplicationELB",
                metricName: "RequestCount",
                dimensionsMap: {
                  "LoadBalancer": "test"
                },
                statistic: "Sum",
                period: cdk.Duration.seconds(60)
          })
        }
      }),
      threshold: 1,
      comparisonOperator: cloudwatch.ComparisonOperator.GREATER_THAN_OR_EQUAL_TO_THRESHOLD
    });

    const cfnAlarm = alarm.node.defaultChild as cloudwatch.CfnAlarm;
    cfnAlarm.addPropertyOverride('Metrics.0.Period', 60);
  }
}

[hakenmt]

Thanks, yes, ended up with that workaround after submitting this bug report.