Aws-sam-cli: Event Type S3 doesn't support name reference

[solivaf]

Hi all,

I am trying to use Event Source S3 Type with Bucket property value as name and not a reference, but I receive an error from SAM

Failed to create the changeset: Waiter ChangeSetCreateComplete failed: Waiter encountered a terminal failure state Status: FAILED. Reason: Transform AWS::Serverless-2016-10-31 failed with: Invalid Serverless Application Specification document. Number of errors found: 1. Resource with id [FooFunction] is invalid. Event with id [EntryFileCreated] is invalid. S3 events must reference an S3 bucket in the same template.

My template.yaml is below.

AWSTemplateFormatVersion : '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Resources:
  FooFunction:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName: EntryFile
      Policies:
        - AmazonS3FullAccess
        - AmazonDynamoDBFullAccess
      Handler: entry.lambda_handler
      Runtime: python3.6
      Events:
        EntryFileCreated:
          Type: S3
          Properties:
            Bucket: foo-bucket
            Events: s3:ObjectCreated:*
            Filter:
              S3Key:
                Rules:
                  - Name: prefix
                    Value: entry/

BTW, if I use a Reference (as you can see below) , SAM tries to create a new resource instead of use one that already exists.

AWSTemplateFormatVersion : '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Resources:
  FooFunction:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName: EntryFile
      Policies:
        - AmazonS3FullAccess
        - AmazonDynamoDBFullAccess
      Handler: entry.lambda_handler
      Runtime: python3.6
      Events:
        EntryFileCreated:
          Type: S3
          Properties:
            Bucket: !Ref Bucket
            Events: s3:ObjectCreated:*
            Filter:
              S3Key:
                Rules:
                  - Name: prefix
                    Value: entry/
    Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: "foo-bucket"

If I use the model above, I receive the error below from CloudFormation.

The following resource(s) failed to create: [Bucket]. . Rollback requested by user. foo-bucket already exists.

I am not sure if I am mistaken or something but it seems a bug.

[iph]

I think in this case, we got a sucky case of CloudFormation does not support adoption of resources like that.

If foo-bucket already exists (which it does), then you need to create a different name for the bucket in order for it to work. If this bucket is important, you may want to open a feature request with SAM: https://github.com/awslabs/serverless-application-model and ask for s3 bucket referencing outside of the cloudformation template. My guess is it is some sort of intrinsic-y goodness that would hold back that feature, but that's just my guess.

[jfuss]

@iph and @solivaf Unfortunately, we need CloudFormation to allow adoption of existing resources. SAM is pretty helpless in this area since SAM is built on top of CloudFormation. Once CloudFormation allows this adoption, SAM will support it (hopefully at launch). There is some more information here.

There was one workaround suggested in that issue, if creating a new bucket through CloudFormation is not an option (as @iph suggested): "Faced this limitation recently and workaround it with combination of S3->SNS and SAM<-SNS. Works pretty good and completely automated." - @sanyer

[programmieramt]

I have the same problem I want to use our cloudtrail Logging bucket to access with my SAM application.
Are there any news on that issue?

[hardingmatt]

+1

I would also really like this feature. My use case is:

• I have an existing S3 bucket of user-provided images
• I would like to use an application from the AWS Serverless Application Repository to add automatic image re-scaling to this bucket.

Unfortunately, the easiest workaround is:

1. Use the Serverless Application Repository to create a new bucket with image re-scaling
2. Change my API to write to both locations, and migrate all old images
3. Change my API to read from new bucket
4. Delete old bucket

Links:

• Image resizing application: chankh/lambda-s3-thumbnail
• Original request

[sanathkr]

This is a SAM repository feature request and not a SAM CLI one. I would encourage you to add the request to https://github.com/awslabs/serverless-application-model if one is not already available.

Closing this

[kylegordon]

This appears to be already raised as an issue at https://github.com/awslabs/serverless-application-model/issues/124