How to refer the environment variable value for s3 bucket name in sam template? - amazon-s3

Question

I am trying to build s3 event application by referring the environment variable defined.
Below the template i am referring
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
CreateThumbnail:
Type: AWS::Serverless::Function
Properties:
Handler: handler
Runtime: runtime
Timeout: 60
Policies: AWSLambdaExecute
Environment:
Variables:
BUCKET_NAME: !Sub "${S3}"
Events:
CreateThumbnailEvent:
Type: S3
Properties:
Bucket: ""How can refer the s3 bucket form the environment here"
Events: s3:ObjectCreated:*
i actually need to refer the 'BUCKET NAME' from the 'Environment variable' and also need to add event trigger from the same s3.
can anyone help on this?
Thanks

Answer 1

There are two options,
Either you have defined the S3 bucket in the same template, and then you can reference it using the logical CFN ID:
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
S3Bucket:
Type: AWS::S3::Bucket
Properties:
BucketName: my-bucket-name
CreateThumbnail:
Type: AWS::Serverless::Function
Properties:
Handler: handler
Runtime: runtime
Timeout: 60
Policies: AWSLambdaExecute
Environment:
Variables:
BUCKET_NAME: !Ref S3Bucket
Events:
CreateThumbnailEvent:
Type: S3
Properties:
Bucket: !Ref S3Bucket
Events: s3:ObjectCreated:*
Or you do not have it defined in the same template, in which case you have to pass it to the stack as a parameter during deployment like this:
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Parameters:
S3Bucket:
Description: Name of the S3 Bucket
Type: String
Resources:
CreateThumbnail:
Type: AWS::Serverless::Function
Properties:
Handler: handler
Runtime: runtime
Timeout: 60
Policies: AWSLambdaExecute
Environment:
Variables:
BUCKET_NAME: !Ref S3Bucket
Events:
CreateThumbnailEvent:
Type: S3
Properties:
Bucket: !Ref S3Bucket
Events: s3:ObjectCreated:*