docs: improve documentation for docker-autoscaler setup

docs/usage.md

@@ -145,54 +145,33 @@ module "runner" {
 
 ### Scenario: Use of Docker autoscaler
 
-As docker machine is no longer maintained by docker, gitlab recently developed docker autoscaler to replace docker machine
-(still in beta). An option is available to test it out.
-
-Tested with amazon-linux-2-x86 as runner manager and ubuntu-server-22-lts-x86 for runner worker. The following commands have been
-added to the original AMI for the runner worker for the docker-autoscaler to work correctly:
-
-```bash
-# Install docker
-# Add Docker's official GPG key:
-apt-get update
-apt-get install -y ca-certificates curl
-install -m 0755 -d /etc/apt/keyrings
-curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
-chmod a+r /etc/apt/keyrings/docker.asc
-
-# Add the repository to Apt sources:
-echo \
-  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
-  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
-  tee /etc/apt/sources.list.d/docker.list > /dev/null
-apt-get update
-
-apt-get install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
-usermod -aG docker ubuntu
-```
+As docker machine is no longer maintained by Docker, GitLab recently developed docker autoscaler to replace docker machine.
+
+Tested with amazon-linux-2-x86 as runner manager and ubuntu-server-22-lts-x86 for runner worker. The main problem is to find an AMI
+which has the Docker engine pre-installed. This means that any "base" Amazon Linux or Ubuntu AMI cannot work.
+
+There is a project in the early alpha phase to support you to build your own AMI: https://github.com/cattle-ops/AWS-Fleeting-Plugin-AMI
 
 #### Docker Autoscaler Configuration
 
 ```hcl
 module "runner" {
-  # https://registry.terraform.io/modules/cattle-ops/gitlab-runner/aws/
-  source  = "cattle-ops/gitlab-runner/aws"
+  source = "cattle-ops/gitlab-runner/aws"
 
-  vpc_id    = module.vpc.vpc_id
+  vpc_id = module.vpc.vpc_id
   subnet_id = element(module.vpc.private_subnets, 0)
 
   runner_gitlab = {
-    tag_list = "runner_worker"
-    type     = "instance"
     url      = "https://gitlab.com"
-
     preregistered_runner_token_ssm_parameter_name = "my-gitlab-runner-token-ssm-parameter-name"
   }
-  
-  runner_manager = {
-    maximum_concurrent_jobs   = 5
+
+  runner_ami_filter = {
+    name = ["amazon-linux-2-x86"]
   }
 
+  runner_ami_owners = ["amazon"]
+
   runner_worker = {
     max_jobs            = 5
     request_concurrency = 5
@@ -202,19 +181,19 @@ module "runner" {
   runner_worker_docker_autoscaler_asg = {
     on_demand_percentage_above_base_capacity = 0
     enable_mixed_instances_policy            = true
-    idle_time                                = 600
-    subnet_ids                               = vpc.private_subnets_ids
-    types                                    = ["t3a.medium", "t3.medium"]
-    volume_type                              = "gp3"
-    private_address_only                     = true
-    ebs_optimized                            = true
-    root_size                                = 40
+    subnet_ids                               = module.vpc.private_subnets
+    types = ["t3a.medium", "t3.medium"]
   }
 
   runner_worker_docker_autoscaler = {
-    connector_config_user = "ubuntu"
+    connector_config_user = "ubuntu" # this user id is used to connect to the instance via SSH
+  }
+
+  runner_worker_docker_autoscaler_ami_filter = {
+    name = ["ubuntu-server-22-lts-x86-*"]
   }
 
+  runner_worker_docker_autoscaler_ami_owners = ["099720109477"] # Canonical
 }
 ```
 

examples/runner-fleeting-plugin/main.tf

@@ -56,13 +56,8 @@ module "runner" {
   subnet_id = element(module.vpc.private_subnets, 0)
 
   runner_instance = {
-    collect_autoscaling_metrics = ["GroupDesiredCapacity", "GroupInServiceCapacity"]
-    name                        = var.runner_name
-    ssm_access                  = true
-  }
-
-  runner_networking = {
-    allow_incoming_ping_security_group_ids = [data.aws_security_group.default.id]
+    name       = var.runner_name
+    ssm_access = true
   }
 
   runner_gitlab = {
@@ -76,23 +71,14 @@ module "runner" {
     max_jobs = 10
   }
 
-  runner_worker_gitlab_pipeline = {
-    pre_build_script  = <<EOT
-        '''
-        echo 'multiline 1'
-        echo 'multiline 2'
-        '''
-        EOT
-    post_build_script = "\"echo 'single line'\""
-  }
-
   runner_worker_docker_autoscaler = {
-    fleeting_plugin_version = "1.0.0"
+    connector_config_user = "ubuntu" # this user id is used to connect to the instance via SSH
   }
 
-  runner_worker_docker_autoscaler_ami_owners = ["591542846629"] # FIXME Change to your AWS account ID
+  # FIXME: this AMI is outdated, but has Docker installed, which is needed. There are no other AMIs available with Docker pre-installed.
+  runner_worker_docker_autoscaler_ami_owners = ["099720109477"] # Canonical
   runner_worker_docker_autoscaler_ami_filter = {
-    name = ["al2023-ami-ecs-hvm-2023.0.20240723-kernel-6.1-x86_64"] # FIXME Change to your AMI name
+    name = ["ubuntu-server-22-lts-x86-*"]
   }
 
   runner_worker_docker_autoscaler_instance = {