Terraform - Optional Nested Variable - amazon-web-services

Question

I'm trying to create a module for Sagemaker endpoints. There's an optional object variable called async_inference_config. If you omit it, the endpoint being deployed is synchronous, but if you include it, the endpoint deployed is asynchronous. To satisfy both of these usecases, the async_inference_config needs to be an optional block.
I am unsure of how to make this block optional though.
Any guidance would be greatly appreciated. See example below of structure of the optional parameter.
Example:
resource "aws_sagemaker_endpoint_configuration" "sagemaker_endpoint_configuration" {
count = var.create ? 1 : 0
name = var.endpoint_configuration_name
production_variants {
instance_type = var.instance_type
initial_instance_count = var.instance_count
model_name = var.model_name
variant_name = var.variant_name
}
async_inference_config {
output_config {
s3_output_path = var.s3_output_path
}
client_config {
max_concurrent_invocations_per_instance = var.max_concurrent_invocations_per_instance
}
}
lifecycle {
create_before_destroy = true
ignore_changes = ["name"]
}
tags = var.tags
depends_on = [aws_sagemaker_model.sagemaker_model]
}
Update: What I tried based on the below suggestion, which seemed to work
dynamic "async_inference_config" {
for_each = var.async_inference_config == null ? [] : [true]
content {
output_config {
s3_output_path = lookup(var.async_inference_config, "s3_output_path", null)
}
client_config {
max_concurrent_invocations_per_instance = lookup(var.async_inference_config, "max_concurrent_invocations_per_instance", null)
}
}
}

Answer 1

You could use a dynamic block [1] in combination with for_each meta-argument [2]. It would look something like:
dynamic "async_inference_config" {
for_each = var.s3_output_path != null && var.max_concurrent_invocations_per_instance != null ? [1] : []
content {
output_config {
s3_output_path = var.s3_output_path
}
client_config {
max_concurrent_invocations_per_instance = var.max_concurrent_invocations_per_instance
}
}
}
Of course, you could come up with a different variable, say enable_async_inference_config (probalby of type bool) and base the for_each on that, e.g.:
dynamic "async_inference_config" {
for_each = var.enable_async_inference_config ? [1] : []
content {
output_config {
s3_output_path = var.s3_output_path
}
client_config {
max_concurrent_invocations_per_instance = var.max_concurrent_invocations_per_instance
}
}
}
[1] https://www.terraform.io/language/expressions/dynamic-blocks
[2] https://www.terraform.io/language/meta-arguments/for_each