How can I add a AWS cloudwatch event to a aws_lambda_function which is based on a container image with terraform? - aws-lambda

Question

I want to achieve that my lambda function which is based on a docker image in ecr is triggered by a scheduled cloudwatch event.
The problem is that I can not attach the function_name myFunction from the module "lambda_function_container_image" to the aws_lambda_permission.
It works when I have a normal lambda function like, but not with the lambda function from a image URI:
resource "aws_lambda_function" "myFunction" {
function_name = "myFunction"
role = aws_iam_role.lambda_execution_role.arn
handler = "exports.handler"
runtime = "python3.8"
}
I have the following code:
AWS CloudWatch event:
resource "aws_cloudwatch_event_rule" "every_five_minutes" {
name = "every-five-minutes"
description = "Fires every five minutes"
schedule_expression = "rate(5 minutes)"
}
Lambda function based on container image:
module "lambda_function_container_image" {
source = "terraform-aws-modules/lambda/aws"
function_name = "myFunction"
description = "awesome function"
create_package = false
image_uri = "${data.aws_caller_identity.current.account_id}.dkr.ecr${var.aws_region}.amazonaws.com/container_name"
package_type = "Image"
}
Lambda permission:
resource "aws_lambda_permission" "allow_cloudwatch_to_call_myFunction" {
statement_id = "AllowExecutionFromCloudWatch"
action = "lambda:InvokeFunction"
function_name = aws_lambda_function.myFunction.function_name
principal = "events.amazonaws.com"
source_arn = aws_cloudwatch_event_rule.every_five_minutes.arn
}
I get the following error with the current aws_lambda_permission:
Error message:
Error: Reference to undeclared resource
-> points to function_name in aws_lambda_permission

Answer 1

You need to reference function_name through the module you are using. According to the documentation of terraform-aws-modules/lambda/aws the module has an output called lambda_function_name.
That means, that the following should work for you:
resource "aws_lambda_permission" "allow_cloudwatch_to_call_myFunction" {
[...]
function_name = module.lambda_function_container_image.lambda_function_name
[...]
}