(aws-backup): Resolution error: stack.regionalFact is not a function

What is the problem?

Trying to follow the guide in https://docs.aws.amazon.com/cdk/api/v1/docs/aws-backup-readme.html to setup backups for tables.

Reproduction Steps

Here’s the simple stack file I tried to reproduce from given the backup guide mentioned above:

import * as cdk from "@aws-cdk/core";
import * as dynamodb from "@aws-cdk/aws-dynamodb";
import * as backup from "@aws-cdk/aws-backup";

export class DynamoTestStack extends cdk.Stack {
    constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
        super(scope, id);

        const plan = backup.BackupPlan.dailyWeeklyMonthly5YearRetention(
            this,
            "Plan"
        );

        const myTable = dynamodb.Table.fromTableName(this, 'Table', 'testtable');

        plan.addSelection("Selection", {
            resources: [backup.BackupResource.fromDynamoDbTable(myTable)]
        });
    }
}

What did you expect to happen?

cdk should have synthesized a template that has logic to backup the table.

What actually happened?

It errors out saying stack.regionalFact isn’t a function although going through the source code shows it is here https://github.com/aws/aws-cdk/blob/77144f5a1072feea7409b4222fbc80bd2bc86e71/packages/%40aws-cdk/core/lib/stack.ts#L825 Tracing the issue, it may lie in aws-iam rather than aws-backup.

Stack trace (censored out identifying information from paths):

infra/cdk/node_modules/@aws-cdk/aws-backup/node_modules/@aws-cdk/aws-iam/lib/principals.ts:540
    return stack.regionalFact(
                 ^
TypeError: Resolution error: Resolution error: Resolution error: Resolution error: stack.regionalFact is not a function.
Object creation stack:
  at stack traces disabled.
Object creation stack:
  at stack traces disabled..
    at ServicePrincipalToken.resolve (infra/cdk/node_modules/@aws-cdk/aws-backup/node_modules/@aws-cdk/aws-iam/lib/principals.ts:540:18)
    at RememberingTokenResolver.resolveToken (infra/cdk/node_modules/@aws-cdk/core/lib/resolvable.ts:80:24)
    at RememberingTokenResolver.resolveToken (infra/cdk/node_modules/@aws-cdk/core/lib/private/resolve.ts:286:18)
    at resolve (infra/cdk/node_modules/@aws-cdk/core/lib/private/resolve.ts:212:51)
    at Object.resolve [as mapToken] (infra/cdk/node_modules/@aws-cdk/core/lib/private/resolve.ts:119:77)
    at TokenizedStringFragments.mapTokens (infra/cdk/node_modules/@aws-cdk/core/lib/string-fragments.ts:65:33)
    at RememberingTokenResolver.resolveString (infra/cdk/node_modules/@aws-cdk/core/lib/resolvable.ts:99:22)
    at RememberingTokenResolver.resolveString (infra/cdk/node_modules/@aws-cdk/core/lib/private/resolve.ts:290:23)
    at resolve (infra/cdk/node_modules/@aws-cdk/core/lib/private/resolve.ts:170:48)
    at Object.resolve (infra/cdk/node_modules/@aws-cdk/core/lib/private/resolve.ts:119:77)   

CDK CLI Version

1.134.0 (build dd5e12d)

Framework Version

No response

Node.js Version

v16.13.0

OS

macOS Catalina

Language

Typescript

Language Version

3.9.7

Other information

Something interesting is that I looked around for other examples of this and came across this repository https://github.com/boostercloud/rocket-backup-aws-infrastructure I downgraded all of my aws-cdk packages to 1.67.0 to match their versions and cdk synth worked afterward. However, it’s unideal to be on version 1.67.0 due to other stacks.

Initially, my dependencies were 1.137.0 for aws-backup, aws-dynamodb, and aws-core.

[kaizencc]

I am able to cdk synth the stack you provided successfully both on the latest v1 version (1.137).

It’s likely that the issue is that your dependencies were not aligned. stack.regionalFact was added 20 days ago, and released in v 1.137. I was able to reproduce the error you are describing by forcing my aws-backup dependency to 1.137 while keeping core at 1.136. backup is searching for a function added in 1.137 but it only has 1.136 available.

Please update @aws-cdk/core to 1.137. I’m almost certain that that will solve the issue.

[peterwoodworth]

Something to note - if you use CDK v2, all the libraries are condensed into one package, and you won’t be able to run into these types of errors anymore!