AWS CDK look up ARNs from lambda - amazon-web-services

Question

I am quite new to AWS and have a maybe easy to answer question.
(I am using localstack to develope locally, if this makes any difference)
In a lambda, I got the following code, which should publish a message to an aws-sns.
def handler(event, context):
logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)
logger.info("confirmed user!")
notification = "A test"
client = boto3.client('sns')
response = client.publish(
TargetArn="arn:aws:sns:us-east-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
Message=json.dumps({'default': notification}),
MessageStructure='json'
)
return {
'statusCode': 200,
'body': json.dumps(response)
}
For now I "hardcode" the ARN of the sns topic which is output to console when deploying (with cdklocal deploy).
I am wondering, if there is any convenient way, to lookup the ARN of a AWS ressource?
I have seen, there is the
cdk.Fn.getAtt(logicalId, 'Arn').toString();
function, but I don't know the logicalID of the sns before deployment. So, how can I lookup ARNs during runtime? What is best practice?
(It's a quite annoying task keeping track of all the ARNs if I just hardcode them as strings, and definitly seems wrong to me)

Answer 1

You can use the !GetAtt function in your CloudFormation template to retrieve and pass your SNS topic ARN to to your Lambda.
Resources:
MyTopic:
Type: AWS::SNS::Topic
Properties:
{...}
MyLambda:
Type: AWS::Lambda::Function
Properties:
Environment:
Variables:
SNS_TOPIC_ARN: !GetAtt MyTopic.Arn