how to refer sns arn from terraform code in a lambda python py file? - aws-lambda

Question

my lambda python uses SNS topic arn. But this sns arn id is generated from terraform code. Is there way to refer it somehow in python lambda code?
def lambda_handler(event, context):
try:
#some code
publish_vote(vote, voter)
except:
#some code
return {'statusCode': 200, 'body': '{"status": "success"}'}
def publish_vote(vote, voter):
sns = boto3.client('sns', region_name='us-east-1')
sns.publish(
TopicArn='arn:aws:sns:us-east-1:025416187662:erjan',
Message='""',
MessageAttributes={
"vote": {
"DataType": "String",
"StringValue": vote,
},
"voter": {
"DataType": "String",
"StringValue": voter,
}
}
)
SNS terraform code:
resource "aws_sns_topic" "vote_sns" {
name = "erjan-sns"
}
resource "aws_sns_topic_policy" "vote_sns_access_policy" {
arn = aws_sns_topic.vote_sns.arn
policy = data.aws_iam_policy_document.vote_sns_access_policy.json
}
data "aws_iam_policy_document" "vote_sns_access_policy" {
policy_id = "__default_policy_ID"
statement {
#some stuff code
}
}
output "sns_arn_erjan" {
value = aws_sns_topic.vote_sns.arn
description = "aws full sns topic"
}

Answer 1

For your information:
I see you have already solved this problem, but I have one suggestion.
The lambda function can refer to the topic ARN by putting the ARN as a parameter into Parameter Store with Terraform.
resource "aws_ssm_parameter" "vote_sns" {
name = "sns_arn_erjan"
type = "String"
value = aws_sns_topic.vote_sns.arn
}
aws_ssm_parameter | Resources | hashicorp/aws | Terraform Registry
The lambda function can refer to the parameter stored in Parameter Store using boto3.
get_parameter - SSM — Boto3 Docs 1.26.54 documentation

Answer 2

Your terraform code does not have code for creating the lambda function itself. Are you creating it manually? If yes, then first create that as well using terraform. A basic example is mentioned here
Within the definition, there is an argument for environment. Use that to define your env variables as:
environment {
variables = {
SNS_ARN = aws_sns_topic.vote_sns.arn # Arn from the defined sns resource.
}
}
Then refer the same in your python code as:
import os
SNS_ARN = os.environ.get("SNS_ARN")
...
Alternatively, you could also consider using AWS SAM