NestedStack parent resource reference generates Circular Dependency

[xoadrian]

I have the following stack structure:

Root(Stack) => AppSync(NestedStack) => Resolvers(NestedStack)

In AppSync(NestedStack) I am creating API, schema and instantiating nested stack for Resolvers, main reason for this this that there are many resolvers and to not hit 200 Resrouce limit I will be manually splitting resources between multiple Resolvers nested stack. Currently I don't know an automated way for splitting resources, if there is please, please share :).

I also tried changing the structure to have nested stacks as siblings, which get's rid of Circular dependency but then it just fails on deploy:

Root(Stack) => AppSync(NestedStack) => ApiStack(NestedStack)
                                    => Resolvers(NestedStack)

creating CloudFormation changeset...
 0/3 | 2:07:56 PM | CREATE_IN_PROGRESS   | AWS::CDK::Metadata         | CDKMetadata
 0/3 | 2:07:56 PM | CREATE_IN_PROGRESS   | AWS::CloudFormation::Stack | appsync-bizon.NestedStack/appsync-bizon.NestedStackResource (appsyncbizonNestedStackappsyncbizonNestedStackResource814A53CF)
 0/3 | 2:07:57 PM | CREATE_IN_PROGRESS   | AWS::CloudFormation::Stack | appsync-bizon.NestedStack/appsync-bizon.NestedStackResource (appsyncbizonNestedStackappsyncbizonNestedStackResource814A53CF) Resource creation Initiated
 0/3 | 2:07:58 PM | CREATE_IN_PROGRESS   | AWS::CDK::Metadata         | CDKMetadata Resource creation Initiated
 1/3 | 2:07:58 PM | CREATE_COMPLETE      | AWS::CDK::Metadata         | CDKMetadata
 2/3 | 2:08:19 PM | CREATE_FAILED        | AWS::CloudFormation::Stack | appsync-bizon.NestedStack/appsync-bizon.NestedStackResource (appsyncbizonNestedStackappsyncbizonNestedStackResource814A53CF) Embedded stack arn:aws:cloudformation:eu-west-2:452364846299:stack/ProductName-bizon-appsyncbizonNestedStackappsyncbizonNestedStackResource814A53CF-4NAE12ZLOQGT/a92a4b40-3c46-11ea-9fec-06452e71541c was not successfully created: The following resource(s) failed to create: [dynamodbstackbizonNestedStackdynamodbstackbizonNestedStackResource0AACEAF0, productnameresolversNestedStackproductnameresolversNestedStackResource42DF9B6A].

Reproduction Steps

cdk.ts:

new RootStack(app, getResourceName(PRODUCT_NAME), {
  tags: TAGS
});

root-stack.ts:

new AppSyncStack(this, getResourceName('appsync'));

appsync-stack.ts

  export class AppSyncStack extends cfn.NestedStack {
  public readonly api: CfnGraphQLApi;
  public readonly schema: CfnGraphQLSchema;

  constructor(scope: cdk.Construct, id: string, props?: cfn.NestedStackProps) {
    super(scope, id, props);

    this.api = this.create();
    this.schema = this.createSchema();
    this.createTable();
    this.createResolvers();
  }

  private create(): CfnGraphQLApi {
    const name = getResourceName(`${getProductName()}-appsync`);
    return new CfnGraphQLApi(this, name, {
      name,
      authenticationType: 'AMAZON_COGNITO_USER_POOLS',
      additionalAuthenticationProviders: [{
        authenticationType: 'API_KEY'
      }]
    });
  }

  private createSchema(): CfnGraphQLSchema {
    return new CfnGraphQLSchema(this, getResourceName(`${getProductName()}-schema`), {
      apiId: this.api.attrApiId,
      definition: fs.readFileSync(SCHEMA_FILE_PATH).toString()
    });
  }

  private createTable(): void {
    // tslint:disable-next-line:no-unused-expression
    new DynamoDbStack(this, getResourceName('dynamodb-stack'));
  }

  private createResolvers(): void {
    // tslint:disable-next-line:no-unused-expression
    new ResolversStack(this, getResourceName(`${getProductName()}-resolvers`),{
      parameters: {
        apiId: this.api.attrApiId
      }
    });
  }
}

resolvers-stack:

new CfnResolver(this, name, {
  typeName,
  fieldName,
  requestMappingTemplate,
  responseMappingTemplate,
  apiId: this.props?.parameters?.apiId || '',
});

Error Log

creating CloudFormation changeset...

 ❌  ProducName-bizon failed: ValidationError: Circular dependency between resources: [appsyncbizonNestedStackappsyncbizonNestedStackResource814A53CF]
Circular dependency between resources: [appsyncbizonNestedStackappsyncbizonNestedStackResource814A53CF]

CFN template generates reference to itself(root-stack.template):

"appsyncbizonNestedStackappsyncbizonNestedStackResource814A53CF": {
      "Type": "AWS::CloudFormation::Stack",
      "Properties": {
        ...
        },
        "Parameters": {
          "referencetoProductNamebizonappsyncbizonproductnameappsyncbizon6498FF74ApiId": {
            "Fn::GetAtt": [
              "appsyncbizonNestedStackappsyncbizonNestedStackResource814A53CF",
              "Outputs.ProuctNamebizonappsyncbizonproductnameappsyncbizon6498FF74ApiId"
            ]
          },

appsync-stack.template:

"productnameresolversbizonNestedStackproductnameresolversbizonNestedStackResource7E007811": {
      "Type": "AWS::CloudFormation::Stack",
      "Properties": {
        ...
        },
        "Parameters": {
          "apiId": {
            "Fn::GetAtt": [
              "productnameappsyncbizon",
              "ApiId"
            ]
          }
        }
      .....
      "Outputs": {
    "ProductNamebizonappsyncbizonprodcutnameappsyncbizon6498FF74ApiId": {
      "Value": {
        "Fn::GetAtt": [
          "productnameappsyncbizon",
          "ApiId"
        ]
      }
    }
  }

resolvers-stack.template:

{
  "Resources": {
    "AreaprimaryContact": {
      "Type": "AWS::AppSync::Resolver",
      "Properties": {
        "ApiId": {
          "Ref": "referencetoProductNamebizonappsyncbizonproductnameappsyncbizon6498FF74ApiId"
        },
        "FieldName": "primaryContact",
        "TypeName": "Area",
        "RequestMappingTemplate": "\n\n#set( $customerId = $context.identity.claims.get(\"custom:customer\") )\n#if( $util.isNullOrEmpty($customerId) )\n  #set( $customerId = \"mydev\" )\n#end\n    \n#set( $pk = \"Person#$customerId\" )\n#set( $sk = \"Person#$customerId#$ctx.source.ownerId\" )\n{\n    \"version\": \"2017-02-28\",\n    \"operation\": \"GetItem\",\n    \"key\": {\n        \"pk\": $util.dynamodb.toDynamoDBJson($pk),\n        \"sk\": $util.dynamodb.toDynamoDBJson($sk)\n    }\n}\n    ",
        "ResponseMappingTemplate": "\n$util.toJson($ctx.result)\n    "
      },
      "Metadata": {
        "aws:cdk:path": "ProductName-bizon/appsync-bizon/productname-resolvers-bizon/Area.primaryContact"
      }
    }
  }
}

Environment

• CLI Version: 1.21.0
• Framework Version:
• OS: Windows
• Language: Typescript

Other

---

This is 🐛 Bug Report

[xoadrian]

@eladb Based on the history you are most related to NestedStack, maybe you can have a quick look over it? I have debugged it:

const factory = this.determineCrossReferenceFactory(targetStack);
// if one side is a nested stack (has "parentStack"), we let it create the reference
// since it has more knowledge about the world.
const consumedValue = factory.prepareCrossReference(this, reference);

In the above stack structure factory is same with target, so in the context of the above issue AppSyncStack is invoking prepareCrossReference and the target is also AppSyncStack

and it falls under the 1st condition from inside. Even if stacks are siblings it still doesn't work even though there is no Circular Dependency validation error in that case. The deploy just fails.

[shivlaks]

@xoadrian - thanks for reporting. I'll take a look later today and run through your reproduction steps