feat: add amazonec2 userdata for docker machines (#608)

Introducing support for amazonec2-userdata flag that is not mentioned on driver readme page, but it is there and useful.

For example, it can be used to introduce swap for the runner instance or any other user command.

Co-authored-by: Alexey Shevchenko <o.shevchenko@relay42.com>
Co-authored-by: kayma <kayma@hlag.com>

examples/runner-default/main.tf

@@ -142,6 +142,13 @@ module "runner" {
   #   command    = ["--registry-mirror", "https://mirror.gcr.io"]
   #   entrypoint = ["dockerd-entrypoint.sh"]
   # }]
+
+
+  # Example how to configure runners, to utilize EC2 user-data feature
+  # example template, creates (configurable) swap file for the runner
+  # runners_userdata = templatefile("${path.module}/../../templates/swap.tpl", {
+  #   swap_size = "512"
+  # })
 }
 
 resource "null_resource" "cancel_spot_requests" {

examples/runner-default/templates/swap.tpl

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+dd if=/dev/zero of=/swapfile bs=1M count=${ coalesce(swap_size, "512") }
+chmod 0600 /swapfile
+mkswap /swapfile
+swapon /swapfile
+
+echo '/swapfile swap swap defaults 0 0' >>/etc/fstab

main.tf

@@ -57,6 +57,7 @@ locals {
       docker_machine_version                       = var.docker_machine_version
       docker_machine_download_url                  = var.docker_machine_download_url
       runners_config                               = local.template_runner_config
+      runners_userdata                             = var.runners_userdata
       runners_executor                             = var.runners_executor
       runners_install_amazon_ecr_credential_helper = var.runners_install_amazon_ecr_credential_helper
       pre_install                                  = var.userdata_pre_install
@@ -98,6 +99,7 @@ locals {
       runners_name                      = var.runners_name
       runners_tags                      = replace(replace(local.runner_tags_string, ",,", ","), "/,$/", "")
       runners_token                     = var.runners_token
+      runners_userdata                  = var.runners_userdata
       runners_executor                  = var.runners_executor
       runners_limit                     = var.runners_limit
       runners_concurrent                = var.runners_concurrent

template/gitlab-runner.tpl

@@ -14,6 +14,10 @@ ${runners_config}
 
 EOF
 
+cat > /etc/gitlab-runner/runners_userdata.sh <<- EOF
+${runners_userdata}
+EOF
+
 sed -i.bak s/__PARENT_TAG__/`echo $PARENT_TAG`/g /etc/gitlab-runner/config.toml
 
 # fetch Runner token from SSM and validate it

template/runner-config.tpl

@@ -65,6 +65,7 @@ listen_address = "${prometheus_listen_address}"
       "amazonec2-iam-instance-profile=%{ if runners_iam_instance_profile_name != "" }${runners_iam_instance_profile_name}%{ else }${runners_instance_profile}%{ endif ~}",
       "amazonec2-root-size=${runners_root_size}",
       "amazonec2-volume-type=${runners_volume_type}",
+      "amazonec2-userdata=%{ if runners_userdata != "" }/etc/gitlab-runner/runners_userdata.sh%{ endif ~}",
       "amazonec2-ami=${runners_ami}"
       ${docker_machine_options}
     ]

variables.tf

@@ -124,6 +124,12 @@ variable "runners_name" {
   type        = string
 }
 
+variable "runners_userdata" {
+  description = "Cloud-init user data that will be passed to the runner ec2 instance. Available only for `docker+machine` driver. Should not be base64 encrypted."
+  type        = string
+  default     = ""
+}
+
 variable "runners_executor" {
   description = "The executor to use. Currently supports `docker+machine` or `docker`."
   type        = string