Aws-cdk: S3 LambdaDestination creates a cyclic reference

Created on 11 Jan 2020 · 7Comments · Source: aws/aws-cdk

Setting S3 Bucket notification to a Lambda function in the other stack creates a cyclic reference.

Reproduction Steps

import * as cdk from "@aws-cdk/core";
import * as lambda from "@aws-cdk/aws-lambda";
import * as s3 from "@aws-cdk/aws-s3";
import * as s3n from "@aws-cdk/aws-s3-notifications";

const app = new cdk.App();
const stack1 = new cdk.Stack(app, "stack1");
const stack2 = new cdk.Stack(app, "stack2");

const lambdaFunction = new lambda.Function(stack1, "lambdaFunction", {
  code: lambda.Code.fromInline("whatever"),
  handler: "index.handler",
  runtime: lambda.Runtime.NODEJS_10_X
});

const bucket = new s3.Bucket(stack2, "bucket");
bucket.addObjectCreatedNotification(new s3n.LambdaDestination(lambdaFunction));

$ cdk synth

Error Log

/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/stack.ts:639
        throw new Error(`'${target.node.path}' depends on '${this.node.path}' (${cycle.join(', ')}). Adding this dependency (${reason}) would create a cyclic reference.`);
              ^
Error: 'stack2' depends on 'stack1' (stack2 -> stack1/lambdaFunction/Resource.Arn, "stack2/bucket/Notifications/Resource" depends on "stack1/lambdaFunction/AllowBucketNotificationsFromstack2bucketA161360C"). Adding this dependency (stack1 -> stack2/bucket/Resource.Arn) would create a cyclic reference.
    at Stack._addAssemblyDependency (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/stack.ts:639:15)
    at Object.addDependency (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/deps.ts:44:20)
    at Stack.addDependency (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/stack.ts:343:5)
    at Stack.prepareCrossReference (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/stack.ts:906:24)
    at Stack.prepare (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/stack.ts:749:37)
    at Function.prepare (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/construct.ts:81:28)
    at Function.synth (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/construct.ts:40:10)
    at App.synth (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/app.ts:141:36)
    at process.<anonymous> (/workspaces/cdk-sample/node_modules/@aws-cdk/core/lib/app.ts:120:45)
    at Object.onceWrapper (events.js:300:26)

Environment

CLI Version : 1.20.0
Framework Version: 1.20.0
OS : All
Language : TypeScript

Other

The resources for the notification seem to have been attached to the stack for Lambda Function and it is causing cyclic reference. Instead, it should be attached to the stack for S3 Bucket.

Passing explicit scope at fn.addPermission() would solve the problem, but I'm not sure it is an appropriate fix or not.