custom implementation of async response logic

Author: Jakeii

ab-testing/cdk/lib/__snapshots__/abTestingStack.test.ts.snap

@@ -239,7 +239,7 @@ exports[`The ID5 Baton Lambda stack > matches the CODE snapshot 1`] = `
                     {
                       "Ref": "AWS::AccountId"
                     },
-                    ":parameter/ab-testing-deploy/CODE/fastly-ab-testing-config"
+                    ":parameter/ab-testing-deploy/CODE/fastly-config"
                   ]
                 ]
               }
@@ -574,7 +574,7 @@ exports[`The ID5 Baton Lambda stack > matches the PROD snapshot 1`] = `
                     {
                       "Ref": "AWS::AccountId"
                     },
-                    ":parameter/ab-testing-deploy/PROD/fastly-ab-testing-config"
+                    ":parameter/ab-testing-deploy/PROD/fastly-config"
                   ]
                 ]
               }

ab-testing/cdk/lib/abTestingStack.ts

@@ -3,7 +3,7 @@ import { GuStack } from "@guardian/cdk/lib/constructs/core/stack.js";
 import { GuLambdaFunction } from "@guardian/cdk/lib/constructs/lambda/index.js";
 import { GuS3Bucket } from "@guardian/cdk/lib/constructs/s3/index.js";
 import type { App } from "aws-cdk-lib";
-import { CustomResource } from "aws-cdk-lib";
+import { CustomResource, Duration } from "aws-cdk-lib";
 import { Runtime } from "aws-cdk-lib/aws-lambda";
 import { StringParameter } from "aws-cdk-lib/aws-ssm";
 
@@ -40,7 +40,7 @@ export class AbTestingStack extends GuStack {
 				this,
 				"FastlyAbTestingConfigParameter",
 				{
-					parameterName: `/${app}/${this.stage}/fastly-ab-testing-config`,
+					parameterName: `/${app}/${this.stage}/fastly-config`,
 				},
 			);
 
@@ -64,6 +64,7 @@ export class AbTestingStack extends GuStack {
 		// Trigger the Lambda to run upon deployment
 		new CustomResource(this, "InvokeDictionaryDeployLambda", {
 			serviceToken: lambda.functionArn,
+			serviceTimeout: Duration.minutes(5),
 		});
 	}
 }

ab-testing/dictionary-deploy-lambda/src/custom-resource-response.ts

@@ -0,0 +1,56 @@
+import type { CloudFormationCustomResourceEvent, Context } from "aws-lambda";
+
+const SUCCESS = "SUCCESS";
+const FAILED = "FAILED";
+
+type Status = typeof SUCCESS | typeof FAILED;
+
+const maskCredentialsAndSignature = (message: string) => {
+	return message
+		.replace(/X-Amz-Credential=[^&\s]+/i, "X-Amz-Credential=*****")
+		.replace(/X-Amz-Signature=[^&\s]+/i, "X-Amz-Signature=*****");
+};
+
+// Modernised implementation of cfn-response's send function using fetch
+// https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-lambda-function-code-cfnresponsemodule.html
+const send = async (
+	event: CloudFormationCustomResourceEvent,
+	context: Context,
+	responseStatus: Status,
+	responseData?: unknown,
+	physicalResourceId?: string,
+) => {
+	const responseBody = JSON.stringify({
+		Status: responseStatus,
+		Reason:
+			"See the details in CloudWatch Log Stream: " +
+			context.logStreamName,
+		PhysicalResourceId: physicalResourceId ?? context.logStreamName,
+		StackId: event.StackId,
+		RequestId: event.RequestId,
+		LogicalResourceId: event.LogicalResourceId,
+		Data: responseData,
+	});
+
+	console.log("Response body:\n", responseBody);
+	console.log("Sending response to:", event.ResponseURL);
+
+	try {
+		await fetch(event.ResponseURL, {
+			method: "PUT",
+			headers: {
+				"content-type": "",
+			},
+			body: responseBody,
+		});
+	} catch (error) {
+		console.log(
+			"send(..) failed executing fetch: " +
+				maskCredentialsAndSignature(String(error)),
+		);
+		throw error;
+	}
+};
+
+export { send, SUCCESS, FAILED };
+export type { Status };

ab-testing/dictionary-deploy-lambda/src/index.ts

@@ -1,10 +1,10 @@
 import { GetParameterCommand, SSMClient } from "@aws-sdk/client-ssm";
 import type { Handler } from "aws-cdk-lib/aws-lambda";
 import type { CloudFormationCustomResourceEvent, Context } from "aws-lambda";
-import { send } from "cfn-response";
 import { assert } from "superstruct";
 import { configStruct } from "../../lib/config.ts";
 import { FastlyClient } from "../../lib/fastly/client.ts";
+import { send } from "./custom-resource-response.ts";
 import { fetchAndDeployArtifacts } from "./deploy.ts";
 
 const getSecureString = async (name: string) => {
@@ -73,13 +73,15 @@ export const handler: Handler = async (
 				},
 			]);
 
-			send(event, context, "SUCCESS");
+			await send(event, context, "SUCCESS");
 		} else {
 			// For Delete requests, simply respond with SUCCESS
-			send(event, context, "SUCCESS");
+			await send(event, context, "SUCCESS");
 		}
 	} catch (error) {
 		console.error("Error deploying dictionaries:", error);
-		send(event, context, "FAILED", { error: (error as Error).message });
+		await send(event, context, "FAILED", {
+			error: (error as Error).message,
+		});
 	}
 };