GitHub Actions Runner Module (ARM64)

The gh-runner-mig-arm64 module provisions ARM64-based GitHub Actions self-hosted runners on GCP using Managed Instance Groups (MIGs).

Overview

Feature	Value
Architecture	ARM64 (T2A / C4A Axion)
Base Image	Ubuntu 22.04 LTS
Container Runtime	Docker-in-Docker
Authentication	GitHub App or PAT
Scaling	Auto-scaling or fixed size
Ephemeral	Single job execution

Key Benefits

• 18-31% faster than x86 equivalents
• 18% cheaper per vCPU-hour
• Native ARM64 support for multi-arch builds
• Enterprise-grade security (Shielded VMs, optional Confidential VMs)

Supported Regions

ARM64 instances are available in these regions:

Region	Available
us-central1	✅
us-east1	✅
us-west1	✅
europe-west1	✅
europe-west4	✅
asia-southeast1	✅
northamerica-northeast1	❌

warning

The project's primary region (northamerica-northeast1) does NOT support ARM64. Runners are deployed to us-central1.

Usage

Basic Example

module "github_runners" {
  source = "../modules/gh-runner-mig-arm64"

  project_id          = var.project_id
  region              = "us-central1"
  network             = google_compute_network.runners.self_link
  subnet              = google_compute_subnetwork.runners.self_link
  github_app_id       = "1998375"
  github_app_private_key = var.github_private_key
  org_name            = "badal-io"
  runner_group        = "badal-arm64-${var.env_type}"
  labels              = ["arm64", "ubuntu", "docker", "gcp", var.env_type]
}

High-Performance Example

module "github_runners_perf" {
  source = "../modules/gh-runner-mig-arm64"

  project_id          = var.project_id
  region              = "us-central1"
  machine_type_cores  = 8
  enable_nvme         = true
  enable_autoscaling  = true
  min_replicas        = 1
  max_replicas        = 10
  target_cpu_utilization = 0.7

  # ... other config
}

Input Variables

Required

Variable	Type	Description
project_id	string	GCP Project ID
network	string	VPC network self_link
subnet	string	Subnet self_link

GitHub Authentication

Variable	Type	Description
github_app_id	string	GitHub App ID
github_app_private_key	string	GitHub App private key (PEM)
github_token	string	Alternative: Personal Access Token
org_name	string	GitHub organization name

Machine Configuration

Variable	Type	Default	Description
machine_type_cores	number	2	vCPUs (1, 2, 4, 8, 16, 32, 48)
region	string	us-central1	GCP region
preemptible	bool	false	Use preemptible instances
enable_nvme	bool	false	Enable NVMe disk interface

Scaling

Variable	Type	Default	Description
target_size	number	1	Fixed instance count
enable_autoscaling	bool	false	Enable CPU-based autoscaling
min_replicas	number	1	Minimum instances
max_replicas	number	10	Maximum instances
target_cpu_utilization	number	0.6	Target CPU for scaling

Security

Variable	Type	Default	Description
enable_shielded_vm	bool	true	Enable Shielded VM features
enable_confidential_vm	bool	false	Enable Confidential Computing
enable_secure_boot	bool	true	Enable Secure Boot
enable_vtpm	bool	true	Enable vTPM
enable_integrity_monitoring	bool	true	Enable Integrity Monitoring

Outputs

Output	Description
instance_template	Instance template self_link
instance_group_manager	MIG self_link
service_account_email	Runner service account
autoscaler	Autoscaler self_link (if enabled)
health_check	Health check self_link

Architecture

Zone Distribution

The module distributes instances across zones for high availability:

zones = ["us-central1-a", "us-central1-b", "us-central1-f"]

note

us-central1-c is excluded as it doesn't support ARM64 instances.

Ephemeral Mode

Runners are configured in ephemeral mode:

1. Runner starts and registers with GitHub
2. Picks up a single job
3. Executes the job
4. Unregisters and terminates
5. MIG replaces with fresh instance

This ensures:

• Clean environment for each job
• No state leakage between jobs
• Automatic security patching via image updates

Related Documentation

• Infrastructure Overview
• GitHub Workflows
• CI/CD Pipeline