AWS lambda SAM deploy error - Template format error: Unresolved resource dependencies

Question

I have am trying to deploy an aws lambda function using the SAM cli. I have some layers defined in the sam template. Testing locally using sam local start-api works quite well. The but deploying using the sam deploy --guided command throws the following error Error: Failed to create changeset for the stack: sam-app, ex: Waiter ChangeSetCreateComplete failed: Waiter encountered a terminal failure state: For expression "Status" we matched expected path: "FAILED" Status: FAILED. Reason: Template format error: Unresolved resource dependencies [arn:aws:lambda:us-west-1:338231645678:layer:ffmpeg:1] in the Resources block of the template Error: Failed to create changeset for the stack: sam-app, ex: Waiter ChangeSetCreateComplete failed: Waiter encountered a terminal failure state: For expression "Status" we matched expected path: "FAILED" Status: FAILED. Reason: Template format error: Unresolved resource dependencies [arn:aws:lambda:us-west-1:338231645678:layer:ffmpeg:1] in the Resources block of the template

The SAM template is as follows

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  video-processor-functions

  Functions to generate gif and thumbnail from uploaded videos
  
# More info about Globals: https://github.com/awslabs/serverless-application-model/blob/master/docs/globals.rst
Globals:
  Function:
    Timeout: 3
    Tracing: Active

Resources:
  VideoProcessorFunctions:
    Type: AWS::Serverless::Function # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction
    Properties:
      CodeUri: src/
      Handler: app.lambdaHandler
      Runtime: nodejs14.x
      # timeout in seconds - 2 minutes
      Timeout: 120
      Layers:
        - !Ref VideoProcessorDepLayer
        - !Ref arn:aws:lambda:us-west-1:338231645678:layer:ffmpeg:1
      Architectures:
        - x86_64
      Events:
        HelloWorld:
          Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
          Properties:
            Path: /hello
            Method: get

  VideoProcessorDepLayer:
    Type: AWS::Serverless::LayerVersion
    Properties:
      LayerName: mh-video-processor-dependencies
      Description: Dependencies for sam app [video-processor-functions]
      ContentUri: dependencies/
      CompatibleRuntimes:
        - nodejs14.17
      LicenseInfo: 'MIT'
      RetentionPolicy: Retain

Outputs:
  # ServerlessRestApi is an implicit API created out of Events key under Serverless::Function
  # Find out more about other implicit resources you can reference within SAM
  # https://github.com/awslabs/serverless-application-model/blob/master/docs/internals/generated_resources.rst#api
  HelloWorldApi:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/hello/"
  VideoProcessorFunctions:
    Description: "Generate GIF and Thumnail from Video"
    Value: !GetAtt VideoProcessorFunctions.Arn
  VideoProcessorFunctionsIamRole:
    Description: "Implicit IAM Role created for MH Video Processor function"
    Value: !GetAtt VideoProcessorFunctionsRole.Arn

Any ideas what i'm doing wrong?

Answer 1

You are trying to reference a logical id that doesn't exist.

Just put the layer's ARN of 'ffmpeg':

Layers:
    - !Ref VideoProcessorDepLayer
    - arn:aws:lambda:us-west-1:338231645678:layer:ffmpeg:1