Terraform: ConcurrentUpdateException: You already have a pending update to an Auto Scaling resource

Question

I'm trying to configure Application Auto Scaling to manage provisioned concurrency in a lambda function via Terraform. Sometimes I get the following exception when running apply :

Error creating application autoscaling target: ConcurrentUpdateException: You already have a pending update to an Auto Scaling resource.
    status code: 400, request id: dd93d5d3-314c-11ea-aeb2-d9246c0fa0b9

  on autoscaling.tf line 1, in resource "aws_appautoscaling_target" "autoscaling-lambda-target":
   1: resource "aws_appautoscaling_target" "autoscaling-lambda-target" {

I know this error occurs if you request an update to an Application Auto Scaling resource that already has a pending update . As I said it happens sometimes . How could I avoid this 100%?

my autoscaling.tf (since there are many lambdas, it runs for each one)

resource "aws_appautoscaling_target" "lambda-target" {

  depends_on = [
    aws_lambda_alias.alias-qa
  ]
  for_each = aws_lambda_function.lambda-function

  max_capacity = local.lambda_functions[each.key].max 
  min_capacity = local.lambda_functions[each.key].min 
  resource_id = "function:${each.value.function_name}:${var.stage}"
  scalable_dimension = "lambda:function:ProvisionedConcurrency"
  service_namespace = "lambda"
}

Answer 1

You could try setting -parallelism=1 so it does not try to do multiple operations at the same time, this will slow down the overall deployment though.