Custom Resource GetAtt not working

[YamiDaisuke]

Guidance Question

Custom Resource GetAtt not working

The Question

Hi!, I'm trying to use a CustomResource to create a MediaTailor channel, so far the scripts go well and the channel gets created but I have two issues:

First problem:

From my lambda function I'm returning the following object:

{
    "Status": "SUCCESS",
    "PhysicalResourceId": "mediaTailorPlaybackConfigName",
    "StackId": "arn:aws:cloudformation:us-east-1:.....",
    "RequestId": "......",
    "LogicalResourceId": "mediaTailorresource7FE79038",
    "Data": {
        "Arn": "arn:aws:mediatailor:us-east-1:XXXXX:playbackConfiguration/mediaTailorPlaybackConfigName",
        "HLS": "https://xxxxxxxxxxxxxxxxxxx.mediatailor.us-east-1.amazonaws.com/v1/master/xxxxxxxxxxx",
        "DASH": "https://xxxxxxxxxxxxxxxxx.mediatailor.us-east-1.amazonaws.com/v1/dash/xxxxxxxxxxxxx"
    }
}

When I try to use resource.getAtt('HLS').toString() I get the following error:

CustomResource attribute error: Vendor response doesn't contain HLS key in object arn:aws:cloudformation:us-east-1:829011433133:stack/xxxxxxxx|mediaTailorResourcexxxxxxxxxxxxxxx in S3 bucket cloudformation-custom-resource-storage-useast1

The second case happens during rollback, even though I'm returning a "PhysicalResourceId" the "DELETE" action receives the same "RequestId" as "PhysicalResourceId" so I don't have a way to find the actual resource and delete it

CDK CLI Version

1.102.0

Example

// For Lambda handler I'm currently using this sample script: 
var response = require('cfn-response');
exports.handler = function (event, context) {
    console.log('REQUEST RECEIVED:\n' + JSON.stringify(event));

    if (event.RequestType === 'Create') {
        console.log('CREATE!');
        response.send(event, context, response.SUCCESS, { 'Message': 'Resource creation successful!', 'HLS': 'hellofromtheotherside.com' });
    } else if (event.RequestType === 'Update') {
        console.log('UDPATE!');
        response.send(event, context, response.SUCCESS, { 'Message': 'Resource update successful!', 'HLS': 'hellofromtheotherside.com' });
    } else if (event.RequestType === 'Delete') {
        console.log('DELETE!');
        response.send(event, context, response.SUCCESS, { 'Message': 'Resource deletion successful!', 'HLS': 'hellofromtheotherside.com' });
    } else {
        console.log('FAILED!');
        response.send(event, context, response.FAILED);
    }
};



// CDK Construct 
class MediaTailorConfig extends cdk.Construct {

    constructor(scope, id, props) {
        super(scope, id, props);

        const onEvent = new lambda.SingletonFunction(this, 'resource', {
            uuid: 'xxxxxxxxxxx',
            code: lambda.Code.fromAsset(path.join(__dirname, 'cfn-mediatailor/index.js.zip'), { encoding: 'utf-8' }),
            handler: 'index.handler',
            timeout: cdk.Duration.seconds(300),
            runtime: lambda.Runtime.NODEJS_14_X,
        });

        const myProvider = new cr.Provider(this, 'MediaTailorProvider', {
            onEventHandler: onEvent,
            logRetention: logs.RetentionDays.TWO_WEEKS, 
        });

        const resource = new cdk.CustomResource(this, 'resource', { serviceToken: myProvider.serviceToken, properties: props });

        this.hls = resource.getAtt('HLS').toString();
    }

}

Example Version

No response

OS

macOS

Language

Typescript

Other information

No response

[bkchy]

We are also having this issue but we are using 2.8.0:

"aws-cdk": "^2.8.0",
"aws-cdk-lib": "^2.8.0",

Is there any update on this or has anyone found a workaround?

[lacteolus]

The same issue with CDK 2.20.0

[mlnrt]

I had the same issue. The way I fixed this is by removing the Provider, and passing the Lambda function ARN directly as the service token.
Essentially doing:

` class MediaTailorConfig extends cdk.Construct {

    constructor(scope, id, props) {
        super(scope, id, props);

        const onEvent = new lambda.SingletonFunction(this, 'resource', {
            uuid: 'xxxxxxxxxxx',
            code: lambda.Code.fromAsset(path.join(__dirname, 'cfn-mediatailor/index.js.zip'), { encoding: 'utf-8' }),
            handler: 'index.handler',
            timeout: cdk.Duration.seconds(300),
            runtime: lambda.Runtime.NODEJS_14_X,
        });

        const resource = new cdk.CustomResource(this, 'resource', { serviceToken: onEvent.functionArn, properties: props });

        this.hls = resource.getAtt('HLS').toString();
    }
}`

[BwL1289]

This was extremely helpful, thank you @mlnrt. Days of debugging and dozens of threads to find this one comment on GH. Docs for AwsCustomResource and Provider are lacking in this area.

[gagipro]

Hello,

same here, the example is extremely confusing and we don't know if it's a bug or a feature...

Thanks @mlnrt

Following this one !

[xiyinzhi]

I ran into the same issue. The way I fix it is removing cfn-response from async lambda handler. I believe the root cause is misusing cfn-response module. While custom resource provider is listening to this lambda, response directly sent by cfn-response will not be received by provider and cause the missing of data in provider response. Instead, we can directly wrap the response and send it back to provider.

Providing an example:

lambda handler:

export const handler = async (event: CdkCustomResourceEvent): Promise<CdkCustomResourceResponse> => {
......
    return {
      Data: {
        AccountId: '000011112222',
      },
    };
};

Alternatively, if you don't want to use CdkCustomResourceResponse you can simply send the data back:

    return {AccountId: '000011112222'};

CDK Construct:

class abcLambda extends Construct {

    constructor(scope, id, props) {
        super(scope, id, props);

        const onEvent = new SingletonFunction(this, 'resource', {
            uuid: 'xxxxxxxxxxx',
            code: Code.fromAsset(path.join(__dirname, '......'), { encoding: 'utf-8' }),
            handler: 'index.handler',
            timeout: Duration.seconds(300),
            runtime: Runtime.NODEJS_14_X,
        });
    
        const provider = new Provider(this, 'Provider', {
          onEventHandler: onEvent,
        });
    
        const cr = new CustomResource(this, `lambda-${name}`, {
          serviceToken: provider.serviceToken,
          properties: {
            name: name,
            date: new Date().toISOString(),
          },
        });
    
        return cr.getAttString('AccountId');
        }

}

ref:
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-lambda-function-code-cfnresponsemodule.html
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources.html