feat: add lambda invocation failure alarm

src/alarms/__tests__/lambda-alarms.test.ts

@@ -0,0 +1,26 @@
+import "@aws-cdk/assert/jest"
+import { App, Stack } from "aws-cdk-lib"
+import * as cloudwatchActions from "aws-cdk-lib/aws-cloudwatch-actions"
+import * as sns from "aws-cdk-lib/aws-sns"
+import "jest-cdk-snapshot"
+import { LambdaAlarms } from "../lambda-alarms"
+
+test("create alarms", () => {
+  const app = new App()
+  const supportStack = new Stack(app, "SupportStack")
+  const stack = new Stack(app, "Stack")
+
+  const topic = new sns.Topic(supportStack, "Topic")
+  const action = new cloudwatchActions.SnsAction(topic)
+
+  const alarms = new LambdaAlarms(stack, "LambdaAlarms", {
+    actions: [action],
+    lambdaFunctionName: "lambda-function-name",
+  })
+
+  alarms.addInvocationErrorAlarm({
+    appendToAlarmDescription: "Runbook at https://liflig.no",
+  })
+
+  expect(stack).toMatchCdkSnapshot()
+})

src/alarms/lambda-alarms.ts

@@ -0,0 +1,62 @@
+import * as constructs from "constructs"
+import * as cdk from "aws-cdk-lib"
+import * as cloudwatch from "aws-cdk-lib/aws-cloudwatch"
+
+export interface LambdaAlarmsProps {
+  actions: cloudwatch.IAlarmAction[]
+  lambdaFunctionName: string
+}
+
+export class LambdaAlarms extends constructs.Construct {
+  private readonly actions: cloudwatch.IAlarmAction[]
+  private readonly lambdaFunctionName: string
+
+  constructor(
+    scope: constructs.Construct,
+    id: string,
+    props: LambdaAlarmsProps,
+  ) {
+    super(scope, id)
+
+    this.actions = props.actions
+    this.lambdaFunctionName = props.lambdaFunctionName
+  }
+
+  /**
+   * Sets up a CloudWatch Alarm that triggers if the Lambda fails invocations.
+   * This usually happens from uncaught exceptions in the lambda.
+   */
+  addInvocationErrorAlarm(
+    /**
+     * Configuration for an alarm.
+     */
+    props?: {
+      /**
+       * Add extra information to the alarm description, like Runbook URL or steps to triage.
+       */
+      appendToAlarmDescription?: string
+    },
+  ): void {
+    const alarm = new cloudwatch.Metric({
+      metricName: "Errors",
+      namespace: "AWS/Lambda",
+      statistic: "Sum",
+      period: cdk.Duration.seconds(60), // Standard resolution metric has a minimum of 60s period
+      dimensionsMap: {
+        FunctionName: this.lambdaFunctionName,
+      },
+    }).createAlarm(this, "FailedInvocationAlarm", {
+      alarmDescription: `Invocation for '${this.lambdaFunctionName}' failed. ${props?.appendToAlarmDescription ?? ""}`,
+      comparisonOperator:
+        cloudwatch.ComparisonOperator.GREATER_THAN_OR_EQUAL_TO_THRESHOLD,
+      evaluationPeriods: 1,
+      threshold: 1,
+      treatMissingData: cloudwatch.TreatMissingData.IGNORE,
+    })
+
+    this.actions.forEach((action) => {
+      alarm.addAlarmAction(action)
+      alarm.addOkAction(action)
+    })
+  }
+}