Auto scaling fleet of GitLab CI runners

This repo contains infrastructure definitions and configuration for a fleet of GitLab CI runners. Provided tools allow to scale the number of runner instances up and down (to zero) as demand changes.

I decided not to use GitLab's suggested docker-machine approach because:

docker-machine is mostly abandoned, life support from GitLab is barely enough to keep it alive. GitLab themselves are looking for an alternative solution.
I want to be able to choose from a wider set of cloud providers than docker-machine supports. Coding new bindings for docker-machine seems to be a pointless endeavor.
I wanted a project to learn Terraform/Pulumi. Previous two iterations of this project were created with Pulumi and Pulumi Automation API. Pulumi stopped developing bindings for the cloud I use (Yandex Cloud) and my Python code was not as clean as I would like, hence this (third) rewrite to Terraform & Go.

I intend to deploy the runners only for personal use and I aim to architect my infra to incur (next to) zero costs when no CI jobs are running.

Project status

Ready for deployment. Deployed and used regularly by author.

Rewritten to Terraform after Pulumi Automation API and plain Pulumi.

Infrastructure overview

Persistent resources
- S3 bucket that holds base image for cloud VMs
Scaling down to zero on demand
- 0 to N runner hosts: Debian hosts with GitLab runner daemon + Docker executor
- 0 to 1 gateway: a simple cloud VM which has a public IPv4 and acts as a router, firewall, reverse proxy for HTTP API and as a caching proxy for Docker Hub.
- Other required resources (networks, IP addresses, VM images)

Usage

Prepare S3 bucket with a prebaked VM image: build/README.md
Launch fleet manager container: container/README.md

Underlying technology

It's incredible how much power and how easily can a single individual wield thanks to modern tech! This project is made possible by standing on shoulders of giants:

[Ansible](https://docs.ansible.com/) · [cloud-init](https://cloudinit.readthedocs.io/) · [Debian](https://debian.org) · [Docker](https://docs.docker.com/) · [GitHub Actions](https://docs.github.com/actions) · [GitLab CI](https://docs.gitlab.com/ee/ci/) · [GNU Make](https://www.gnu.org/software/make/) · [Golang](https://go.dev) · [GraphQL](https://graphql.org/) · [nftables](https://netfilter.org/projects/nftables/) · [Python](https://python.org) · [Qemu (qemu-utils)](https://www.qemu.org/) · [systemd](https://systemd.io) · [Terraform](https://www.terraform.io/) · [Yandex Cloud](https://cloud.yandex.com) ·

License and copyright

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

sio / gitlab-runners-fleet