terraform-provider-aws: ClientException: Too many concurrent attempts to create a new revision of the specified family.

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Terraform Version

Terraform v0.12.5

Affected Resource(s)

• aws_ecs_task_definition

Terraform Configuration Files

data "template_file" "task_definition__backend" {
  template = file("${path.module}/task_definitions/backend.json")

  vars = {
    image_url = "1111111111111111.dkr.ecr.us-east-1.amazonaws.com/my-repo-here/backend:${var.version_tag}"
    container_name = "backend"

    log_group_region = data.aws_region.current.name
    log_group_name = aws_cloudwatch_log_group.app.name
  }
}

data "template_file" "task_definition__frontend" {
  template = file("${path.module}/task_definitions/frontend.json")

  vars = {
    image_url = "1111111111111111.dkr.ecr.us-east-1.amazonaws.com/my-repo-here/frontend:${var.version_tag}"
    container_name = "frontend"

    log_group_region = data.aws_region.current.name
    log_group_name = aws_cloudwatch_log_group.app.name
  }
}

resource "aws_ecs_task_definition" "backend" {
  family = local.ecs_cluster_name
  container_definitions = data.template_file.task_definition__backend.rendered
  network_mode = "awsvpc"
}
resource "aws_ecs_task_definition" "frontend" {
  family = local.ecs_cluster_name
  container_definitions = data.template_file.task_definition__frontend.rendered
  network_mode = "awsvpc"
}

resource "aws_ecs_service" "backend" {
  name = "${local.ecs_cluster_name}_backend"
  cluster = aws_ecs_cluster.ecs_cluster.id
  task_definition = aws_ecs_task_definition.backend.arn
  desired_count = "1"
  deployment_minimum_healthy_percent = 100
  deployment_maximum_percent = 300
  network_configuration {
    subnets = aws_subnet.private_subnet.*.id
    security_groups = [
      aws_security_group.sg_for_ec2_instances.id]
  }

  load_balancer {
    # Register the ECS service within the ALB target group
    # This makes the service participate in health checks
    # and receive traffic when healthy
    target_group_arn = aws_alb_target_group.target_group_backend.arn
    container_name = "backend"
    container_port = "80"
  }

  service_registries {
    registry_arn = aws_service_discovery_service.service_discovery.arn
    container_name = "backend"
    container_port = 80
  }

  depends_on = [
    aws_alb_listener.http_traffic,
  ]
}
resource "aws_ecs_service" "frontend" {
  name = "${local.ecs_cluster_name}_frontend"
  cluster = aws_ecs_cluster.ecs_cluster.id
  task_definition = aws_ecs_task_definition.frontend.arn
  desired_count = "2"
  deployment_minimum_healthy_percent = 100
  deployment_maximum_percent = 300
  network_configuration {
    subnets = aws_subnet.private_subnet.*.id
    security_groups = [
      aws_security_group.sg_for_ec2_instances.id]
  }

  load_balancer {
    target_group_arn = aws_alb_target_group.target_group_frontend.arn
    container_name = "frontend"
    container_port = "80"
  }

  service_registries {
    registry_arn = aws_service_discovery_service.service_discovery.arn
    container_name = "frontend"
    container_port = 80
  }

  depends_on = [
    aws_alb_listener.http_traffic,
    aws_ecs_service.backend,
  ]
}

Expected Behavior

Running terraform apply again and again should not cause any errors. I expect that AWS task definitions get updated properly.

Actual Behavior

AWS task definitions don’t get updated and an error is thrown approximately 1 out of 5 attempts. If I rerun terraform apply another time, it usually works.

Error: ClientException: Too many concurrent attempts to create a new revision of the specified family.
        status code: 400, request id: efce29cc-a021-4d6b-b603-d84c8b7a91fa

Steps to Reproduce

1. terraform apply

Important Factoids

Nothing special. Just two ECS services and the corresponding task definitions for them. It’s worth noting that they are both within the same “family”. Maybe this has some impact?