serverless.yml

service: s3-to-gcs 

custom:
  pythonRequirements:
    dockerizePip: non-linux

provider:
  name: aws
  runtime: python3.6
  region: eu-central-1

# you can add statements to the Lambda function's IAM Role here
  iamRoleStatements:
    - Effect: "Allow"
      Action:
        - "s3:ListBucket"
      Resource: { "Fn::Join" : ["", ["arn:aws:s3:::", { "Ref" : "ServerlessDeploymentBucket" } ] ]  }
    - Effect: "Allow"
      Action:
        - "s3:PutObject"
      Resource:
        Fn::Join:
          - ""
          - - "arn:aws:s3:::"
            - "Ref" : "ServerlessDeploymentBucket"
            - "/*"
    - Effect: "Allow"
      Action:
        - "s3:GetObject"
      Resource: "arn:aws:s3:::${opt:aws_bucket}/*"
    - Effect: "Allow"
      Action:
        - "s3:PutBucketNotification"
      Resource:
        Fn::Join:
          - ""
          - - "arn:aws:s3:::${opt:aws_bucket}"

functions:
  s3_to_gcs:
    handler: handler.lambda_handler
    events:
      - existingS3:
          bucket: ${opt:aws_bucket}
          events: 
            - s3:ObjectCreated:*
    environment:
      GOOGLE_APPLICATION_CREDENTIALS: service-account.json
      GCS_BUCKET_NAME: ${opt:gcs_bucket}

plugins:
  - serverless-python-requirements
  - serverless-plugin-existing-s3