[cloudwatch] Support alarm warm-up for single-series alarms #38743

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1. github-actions

   added

   needs-triageThis issue or PR still needs to be triaged.This issue or PR still needs to be triaged.

   @aws-cdk/aws-cloudwatchRelated to Amazon CloudWatchRelated to Amazon CloudWatch

   on Sep 2, 2026
2. topra-aws commented on Sep 2, 2026

   

   topra-aws

   on Sep 2, 2026

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   ^Note the entire attached PR is written via AI as I'm not very familiar with typescript. It looked correct as it is just a property on metric and log alarms (no support for composite). I will also update it to remove the promQL support as for promQL we expect to use the pending period to keep it in line with normal prometheus alerts. Also once log alarms construct is written, support should be extended to it as well
3. topra-aws

   changed the title [-][cloudwatch] Support alarm warm-up configuration in L2 alarms[/-] [+][cloudwatch] Support alarm warm-up configuration for single metrics[/+] on Sep 2, 2026
4. topra-aws

   changed the title [-][cloudwatch] Support alarm warm-up configuration for single metrics[/-] [+][cloudwatch] Support alarm warm-up for single-series alarms[/+] on Sep 2, 2026
5. pahud commented on Sep 4, 2026

   

   pahud

   on Sep 4, 2026

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   Thanks for the well-scoped request — and for already opening #38744. This is a valid feature request; I confirmed CfnAlarm.warmUpConfiguration (with WarmUpConfigurationProperty) is present in the shipped aws-cdk-lib 2.268.0 generated L1, so the L2 gap is real.

   Until the PR lands, you (and anyone else finding this issue) can set the property today without raw escape hatches using the CfnAlarmPropsMixin from @aws-cdk/cfn-property-mixins:

   import { CfnAlarmPropsMixin } from '@aws-cdk/cfn-property-mixins/lib/services/aws-cloudwatch';
   
   const alarm = metric.createAlarm(this, 'Alarm', { threshold: 1, evaluationPeriods: 3 });
   alarm.with(new CfnAlarmPropsMixin({
     warmUpConfiguration: {
       warmUpPeriodDurationInMinutes: 15,
       onlyStartEvaluatingAfterWarmUpPeriodEnds: true,
     },
   }));

   On the proposal itself: in my opinion the scoping is sound — single-series alarms only, 1–2880 whole-minute validation with unresolved-token passthrough, rejecting top-level GROUP BY Metrics Insights queries, and your follow-up decision to exclude PromQL (pending period being the Prometheus-native equivalent) all make sense. The note about extending to a future log-alarm L2 is a good call too; for what it's worth, the mixin package already ships a CfnLogAlarmPropsMixin with the same property.

   Since #38744 is already in review, the discussion can continue there. Thanks for contributing!
6. pahud

   added

   p2

   feature-requestA feature should be added or improved.A feature should be added or improved.

   effort/mediumMedium work item – several days of effortMedium work item – several days of effort

   and removed

   needs-triageThis issue or PR still needs to be triaged.This issue or PR still needs to be triaged.

   on Sep 4, 2026
7. pahud commented on Sep 21, 2026

   

   pahud

   on Sep 21, 2026

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   Until this lands as a first-class L2 prop, the CDK Mixins mechanism (GA in aws-cdk-lib) gives a clean, reusable way to set WarmUpConfiguration today — the property is already available on the L1 CfnAlarm.

   Verified with aws-cdk-lib@2.270.0 (compiles under strict TS, synthesizes, and the property appears on the AWS::CloudWatch::Alarm resource):

   import { Mixin, Mixins } from 'aws-cdk-lib';
   import { IConstruct } from 'constructs';
   import * as cloudwatch from 'aws-cdk-lib/aws-cloudwatch';
   
   class AlarmWarmUp extends Mixin {
     constructor(private readonly warmUp: cloudwatch.CfnAlarm.WarmUpConfigurationProperty) {
       super();
     }
     supports(construct: IConstruct): boolean {
       return cloudwatch.CfnAlarm.isCfnAlarm(construct);
     }
     applyTo(construct: IConstruct): void {
       if (!this.supports(construct)) return;
       (construct as cloudwatch.CfnAlarm).warmUpConfiguration = this.warmUp;
     }
   }
   
   const alarm = new cloudwatch.Alarm(this, 'Alarm', {
     metric: new cloudwatch.Metric({ namespace: 'MyApp', metricName: 'Errors' }),
     threshold: 1,
     evaluationPeriods: 3,
   });
   
   Mixins.of(alarm).requireAny().apply(new AlarmWarmUp({
     onlyStartEvaluatingAfterWarmUpPeriodEnds: true,
     warmUpPeriodDurationInMinutes: 15,
   }));

   Synthesized output on the alarm:

   "WarmUpConfiguration": {
     "OnlyStartEvaluatingAfterWarmUpPeriodEnds": true,
     "WarmUpPeriodDurationInMinutes": 15
   }

   Because the mixin targets the L1, it also works when applied to a whole scope (e.g. Mixins.of(stack).apply(...) to warm up every alarm in a stack). requireAny() makes synth fail if nothing matched, so you don't silently no-op.

   Let me know if it works.
8. pahud

   added

   response-requestedWaiting on additional info and feedback. Will move to "closing-soon" in 7 days.Waiting on additional info and feedback. Will move to "closing-soon" in 7 days.

   mixins

   on Sep 21, 2026
9. github-actions commented on Sep 23, 2026

   

   github-actionsBot

   on Sep 23, 2026 – with GitHub Actions

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    closing-soonThis issue will automatically close in 4 days unless further comments are made.This issue will automatically close in 4 days unless further comments are made.

    on Sep 23, 2026
11. github-actions

    closed this as completedon Sep 29, 2026