Export the DynamoDB table Stream Arn as an stack's output

Is your feature request related to a problem? Please describe. Currently, there is no easy way to add a stream event, for example, to trigger a Lambda function, because the Stream Arn is not available in any stack. I’ve created a function using amplify function add, now, I want to edit the template to add an AWS::Lambda::EventSourceMapping but it is not possible except if I hardcoded the Stream Arn in the template, but, It will fail if I create a new environment.

Describe the solution you’d like It will be awesome to have the DynamoDB table Stream Arn as an output, and exported using the process described in aws-amplify/amplify-category-api#440 and we will be able to add an AWS::Lambda::EventSourceMapping config to a function’s template. Something like

"EventSourceMapping": {
	"Type": "AWS::Lambda::EventSourceMapping",
	"Properties": {
		"EventSourceArn": {
			"Fn::ImportValue": {
				"Fn::Join": [":",
                    [
                        { "Fn::Sub": "${ParentStackName}" },
                        "GetAtt",
                        "MyDynamoDBTable",
                        "StreamArn"
                    ]
                ]
			}
		},
		"FunctionName": {
			"Fn::GetAtt": ["LambdaFunction", "Arn"]
		},
		"StartingPosition": "TRIM_HORIZON"
	}
}

[matwerber1]

Hi. Thanks for feedback above. If it helps anyone, I summarized the recommendations above in this project:

https://github.com/matwerber1/aws-amplify-subscribe-lambda-to-dynamodb-api-table-stream/

[kstro21]

Hi, @psporysz, I think it is not a workaround, it is the way to do it. Note you can write it like

"Fn::ImportValue": {
	"Fn::Sub":  "${apiresourcenameGraphQLAPIIdOutput}:GetAtt:MyModelTable:StreamArn"
}

It is easy to read