cdk-infrastructure-monitoring

CloudWatch Alarms

Add alarms for Lambda errors, throttles, duration, and SQS queue depth. Notify via SNS for critical failures.

// cdk/lib/stacks/monitoring-stack.ts

import { Stack, StackProps, Duration } from "aws-cdk-lib";
import { Construct } from "constructs";
import {
  Alarm,
  ComparisonOperator,
  TreatMissingData,
  Metric,
  Stats,
} from "aws-cdk-lib/aws-cloudwatch";
import { SnsAction } from "aws-cdk-lib/aws-cloudwatch-actions";
import { Topic } from "aws-cdk-lib/aws-sns";
import { Function as LambdaFunction } from "aws-cdk-lib/aws-lambda";
import { Queue } from "aws-cdk-lib/aws-sqs";

interface MonitoringStackProps extends StackProps {
  lambdaFunctions: LambdaFunction[];
  queues?: Queue[];
  alarmTopic?: Topic;
}

export class MonitoringStack extends Stack {
  constructor(scope: Construct, id: string, props: MonitoringStackProps) {
    super(scope, id, props);

    const alarmTopic =
      props.alarmTopic ??
      new Topic(this, "AlarmTopic", { displayName: "Real Estate Alarms" });

    for (const fn of props.lambdaFunctions) {
      // Lambda errors
      new Alarm(this, `${fn.node.id}Errors`, {
        alarmName: `${fn.functionName}-errors`,
        metric: fn.metricErrors({ period: Duration.minutes(1) }),
        threshold: 5,
        evaluationPeriods: 1,
        comparisonOperator: ComparisonOperator.GREATER_THAN_THRESHOLD,
        treatMissingData: TreatMissingData.NOT_BREACHING,
        alarmDescription: `Lambda ${fn.functionName} error count`,
      }).addAlarmAction(new SnsAction(alarmTopic));

      // Lambda throttles
      new Alarm(this, `${fn.node.id}Throttles`, {
        alarmName: `${fn.functionName}-throttles`,
        metric: fn.metricThrottles({ period: Duration.minutes(1) }),
        threshold: 1,
        evaluationPeriods: 1,
        comparisonOperator: ComparisonOperator.GREATER_THAN_THRESHOLD,
        treatMissingData: TreatMissingData.NOT_BREACHING,
      }).addAlarmAction(new SnsAction(alarmTopic));

      // Lambda duration (e.g. > 80% of timeout)
      const timeoutMs = fn.timeout?.toMilliseconds() ?? 30000;
      new Alarm(this, `${fn.node.id}Duration`, {
        alarmName: `${fn.functionName}-duration`,
        metric: fn.metricDuration({ period: Duration.minutes(1), statistic: Stats.P99 }),
        threshold: timeoutMs * 0.8,
        evaluationPeriods: 2,
        comparisonOperator: ComparisonOperator.GREATER_THAN_THRESHOLD,
        treatMissingData: TreatMissingData.NOT_BREACHING,
      }).addAlarmAction(new SnsAction(alarmTopic));
    }

    // SQS queue depth (optional)
    for (const queue of props.queues ?? []) {
      new Alarm(this, `QueueDepth-${queue.node.id}`, {
        alarmName: `sqs-${queue.queueName}-depth`,
        metric: new Metric({
          namespace: "AWS/SQS",
          metricName: "ApproximateNumberOfMessagesVisible",
          dimensionsMap: { QueueName: queue.queueName },
          period: Duration.minutes(5),
          statistic: Stats.SUM,
        }),
        threshold: 1000,
        evaluationPeriods: 2,
        comparisonOperator: ComparisonOperator.GREATER_THAN_THRESHOLD,
        treatMissingData: TreatMissingData.NOT_BREACHING,
      }).addAlarmAction(new SnsAction(alarmTopic));
    }
  }
}