blog/content/posts/2022-02-13-build-your-own-docker-swarm-cluster.md

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title	date	description	tags	slug	draft
Setup a Docker Swarm cluster for less than $30 / month	2022-02-13	Build an opinionated containerized platform for developer...	docker swarm	build-your-own-homelab-docker-swarm-cluster	true

{{< lead >}} Build your own cheap while powerful self-hosted complete CI/CD solution by following this opinionated guide 🎉 {{< /lead >}}

Why Docker Swarm 🧐 ?

Because Docker Swarm Rocks !

Even if Docker Swarm has lost the enterprise graduate orchestration containers war, you don't have to throw yourself into all Kubernetes fuzzy complicated things for a simple homelab, unless for custom training of course.

If you know how to use docker-compose, you're already ready for Docker Swarm which use almost the same API with addition of specific deploy config.

I'll try to show you step by step how to install your own cheap containerized cluster for less than $30 by using Hetzner, one of the best Cloud provider on European market, with cheap but powerful VPS.

So the prerequisites before continue :

• Have some knowledge on docker-compose setups
• Be comfortable with SSH terminal
• Registered for a Hetzner Cloud account
• A custom domain, I'll use example.org here
• A account to a transactional mail provider as mailgun, sendgrid, sendingblue, etc.

{{< alert >}} You can of course apply this guide on any other cloud provider, but I doubt that you can achieve lower price. {{< /alert >}}

Final goal 🎯

In the end of this multi-steps guide, you will have complete working production grade secured cluster, backup included, with optional monitoring and complete development CI/CD workflow.

1. Cluster initialization 🌍

• Initial VPS setup for docker under Ubuntu 20.04 with proper Hetzner firewall configuration
• Docker Swarm installation, 1 manager and 2 workers
• Traefik, a cloud native reverse proxy with automatic service discovery and SSL configuration
• Portainer as simple GUI for containers management

2. The stateful part 💾

For all data critical part, I choose to use 1 dedicated VPS. We will install :

• GlusterFS as network filesystem, configured for cluster nodes
• Loki with Promtail for centralized logs, fetched from data node and docker containers
• PostgreSQL as main production database
• MySQL as additional secondary database (optional)

Note as I will not set up this for HA (High Availability) here, as it's a complete another topic. So this data node will be our SPF (Single Point of Failure) with only one file system and DB.

{{< alert >}} There are many debates about using databases as docker container, but I personally prefer use managed server for better control, local on-disk performance, central backup management and easier possibility of database clustering.
Note as on the Kubernetes world, run containerized databases becomes reality thanks to powerful operators that provide easy clustering. The is obviously no such things on Docker Swarm 🙈 {{< /alert >}}

Data Backup (optional)

Because backup should be taken care from the beginning, I'll show you how to use Restic for simple backups to external S3 compatible bucket.

3. Testing the cluster ✅

We will use the main portainer GUI in order to install following tools :

• pgAdmin and phpMyAdmin as web database managers (optional)
• Diun (optional), very useful in order to be notified for all used images update inside your Swarm cluster
• Some demo containerized samples that will show you how simple is it to install self-hosted web apps thanks to your shiny new cluster as redmine, n8n

4. Monitoring 📈

This is an optional part, feel free to skip. We'll set up production grade monitoring and tracing with complete dashboards.

• Prometheus as time series DB for monitoring
  • We will configure many metrics exporter for each critical part (Data node, PostgreSQL, MySQL, containers detail thanks to cAdvisor)
  • Basic usage of PromQL
• Jaeger as tracing tools
  • We will use Elasticsearch as main data storage
• Traefik configuration for metrics and trace as perfect sample
• Grafana as GUI dashboard builder with many battery included dashboards
  • Monitoring all the cluster
  • Node, PostgreSQL and MySQL metrics
  • Navigate through log history of all containers and data server node thanks to Loki like ELK, with LogQL

5. CI/CD setup 💻

• Gitea as lightweight centralized control version, in case you want get out of Github / GitLab Cloud
• Private docker registry with minimal UI for all your custom app images that will be built on your development process and be used as based image for your production docker on cluster
• Drone CI as self-hosted CI/CD solution
• SonarQube as self-hosted quality code control

Finally, we'll finish this guide by a simple mini-app development with above CI/CD integration !

Cluster Architecture 🏘️

Note as this cluster will be intended for developer user with complete self-hosted CI/CD solution. So for a good cluster architecture starting point, we can imagine the following nodes :

• manager-01 : The frontal manager node, with proper reverse proxy and some management tools
• worker-01 : A worker for your production/staging apps
• runner-01 : An additional worker dedicated to CI/CD pipelines execution
• data-01 : The critical data node, with attached and resizable volume for better flexibility

{{< mermaid >}} flowchart TD subgraph manager-01 traefik((Traefik))<-- Container Discovery -->docker[Docker API] end subgraph worker-01 my-app-01((My App 01)) my-app-02((My App 02)) end subgraph runner-01 runner((Drone CI runner)) end subgraph data-01 logs[Loki] postgresql[(PostgreSQL)] files[/GlusterFS/] mysql[(MySQL)] end manager-01 == As Worker Node ==> worker-01 manager-01 == As Worker Node ==> runner-01 traefik -. reverse proxy .-> my-app-01 traefik -. reverse proxy .-> my-app-02 my-app-01 -.-> postgresql my-app-02 -.-> mysql my-app-01 -.-> files my-app-02 -.-> files {{< /mermaid >}}

Note as the hostnames correspond to a particular type of server, dedicated for one task specifically. Each type of node can be scale as you wish :

• manager-0x For advanced resilient Swarm quorum
• worker-0x : For better scaling production apps, the easiest to set up
• runner-0x : More power for pipeline execution
• data-0x : The hard part for data HA, with GlusterFS replications, DB clustering for PostgreSQL and MySQL, etc.

{{< alert >}} For a simple production cluster, you can start with only manager-01 and data-01 as absolutely minimal start.
For a development perspective, you can skip worker-01 and use manager-01 for production running.
You have plenty choices here according to your budget ! {{< /alert >}}

Hetzner VPS 🖥️

Here some of the cheapest VPS options we have :

• CPX11 (AMD) = 2C/2G/40Go = €4.79
• CX21 (Intel) = 3C/4G/80Go = €5.88
• CPX21 (AMD) = 3C/4G/80Go = €8.28

My personal choice for a good balance between cheap and well-balanced cluster :

• manager-01 : CX21, I'll privilege RAM
• runner-01 : CPX11, 2 powerful core is better for building
• worker-01 and data-01 : CX21 VS CPX21 (just a power choice matter)

We'll take additional volume of 60 Go for €2.88

We finally arrive to following respectable budget range : €25.31 - $31.31

The only difference being choice between Xeon VS EPIC as CPU power for worker and data nodes, which will our main production application nodes. A quick sysbench will indicates around 70-80% more power for AMD (test date from 2022-02). Choose wisely according to your needs.

If you don't need of worker and runner nodes, with only one simple standalone docker host without Swarm mode, you can even go down to €14,64 with only 2 CX21 in addition to volume.

{{< alert >}} If you intend to have your own self-hosted GitLab for an enterprise grade CI/CD workflow, you should run it on node with 8 GB of RAM.
4 GB is doable if you run just one single GitLab container on it with Prometheus mode disabled and external PostgreSQL. {{< /alert >}}