feat: support Lambda actions (#597)

Closes #560

---

_By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license_

Author: Eugene Cheung

API.md

@@ -0,0 +1,28 @@
+import { LambdaAction } from "aws-cdk-lib/aws-cloudwatch-actions";
+import { IAlias, IFunction, IVersion } from "aws-cdk-lib/aws-lambda";
+
+import {
+  AlarmActionStrategyProps,
+  IAlarmActionStrategy,
+} from "./IAlarmActionStrategy";
+
+export function triggerLambda(
+  lambdaFunction: IAlias | IVersion | IFunction,
+): IAlarmActionStrategy {
+  return new LambdaAlarmActionStrategy(lambdaFunction);
+}
+
+/**
+ * Alarm action strategy that triggers a Lambda function.
+ */
+export class LambdaAlarmActionStrategy implements IAlarmActionStrategy {
+  protected readonly lambdaFunction: IAlias | IVersion | IFunction;
+
+  constructor(lambdaFunction: IAlias | IVersion | IFunction) {
+    this.lambdaFunction = lambdaFunction;
+  }
+
+  addAlarmActions(props: AlarmActionStrategyProps): void {
+    props.alarm.addAlarmAction(new LambdaAction(this.lambdaFunction));
+  }
+}

lib/common/alarm/action/LambdaAlarmActionStrategy.ts

@@ -1,4 +1,5 @@
 export * from "./IAlarmActionStrategy";
+export * from "./LambdaAlarmActionStrategy";
 export * from "./MultipleAlarmActionStrategy";
 export * from "./NoopAlarmActionStrategy";
 export * from "./OpsItemAlarmActionStrategy";

lib/common/alarm/action/index.ts

@@ -0,0 +1,65 @@
+import { Stack } from "aws-cdk-lib";
+import { Template } from "aws-cdk-lib/assertions";
+import { Alarm, Metric } from "aws-cdk-lib/aws-cloudwatch";
+import { Function, InlineCode, Runtime } from "aws-cdk-lib/aws-lambda";
+
+import { LambdaAlarmActionStrategy } from "../../../../lib";
+
+test("snapshot test: Lambda function", () => {
+  const stack = new Stack();
+  const onAlarmFunction = new Function(stack, "alarmLambda", {
+    functionName: "DummyLambda",
+    runtime: Runtime.NODEJS_18_X,
+    code: InlineCode.fromInline("{}"),
+    handler: "Dummy::handler",
+  });
+  const alarm = new Alarm(stack, "DummyAlarm", {
+    evaluationPeriods: 1,
+    threshold: 0,
+    metric: new Metric({ namespace: "Dummy", metricName: "Dummy" }),
+  });
+  const action = new LambdaAlarmActionStrategy(onAlarmFunction);
+  action.addAlarmActions({ alarm, action });
+
+  expect(Template.fromStack(stack)).toMatchSnapshot();
+});
+
+test("snapshot test: Lambda alias", () => {
+  const stack = new Stack();
+  const onAlarmFunction = new Function(stack, "alarmLambda", {
+    functionName: "DummyLambda",
+    runtime: Runtime.NODEJS_18_X,
+    code: InlineCode.fromInline("{}"),
+    handler: "Dummy::handler",
+  });
+  const alias = onAlarmFunction.addAlias("aliasName");
+  const alarm = new Alarm(stack, "DummyAlarm", {
+    evaluationPeriods: 1,
+    threshold: 0,
+    metric: new Metric({ namespace: "Dummy", metricName: "Dummy" }),
+  });
+  const action = new LambdaAlarmActionStrategy(alias);
+  action.addAlarmActions({ alarm, action });
+
+  expect(Template.fromStack(stack)).toMatchSnapshot();
+});
+
+test("snapshot test: Lambda version", () => {
+  const stack = new Stack();
+  const onAlarmFunction = new Function(stack, "alarmLambda", {
+    functionName: "DummyLambda",
+    runtime: Runtime.NODEJS_18_X,
+    code: InlineCode.fromInline("{}"),
+    handler: "Dummy::handler",
+  });
+  const version = onAlarmFunction.currentVersion;
+  const alarm = new Alarm(stack, "DummyAlarm", {
+    evaluationPeriods: 1,
+    threshold: 0,
+    metric: new Metric({ namespace: "Dummy", metricName: "Dummy" }),
+  });
+  const action = new LambdaAlarmActionStrategy(version);
+  action.addAlarmActions({ alarm, action });
+
+  expect(Template.fromStack(stack)).toMatchSnapshot();
+});