Mastodon on GCP via Terraform

This Terraform project manages the Google Cloud Platform infrastructure necessary for operating the Interledger Foundation's Mastodon instance. This repository is intended to be reusable by other people who want to operate a Mastodon instance using GCP.

Mastodon requires:

• a domain name (Cloud DNS)
• a PostgreSQL database (Cloud SQL)
• a Redis database (Memorystore)
• an S3-compatible object storage (Cloud Storage)
• a Kubernetes cluster (Kubernetes Engine in Autopilot mode)

Additional GCP-specific functionality:

• Global external Application Load Balancer for ingress
• Google-managed TLS certificates
• Ingress rule to redirect http traffic to https

This project was tested on 2024-09-30 with:

• GKE 1.30.3-gke.1969001
• helm 3.16.1
• Mastodon chart 5.4.0 (* see below)
• Mastodon app 4.2.12

How to use

Prerequisites

This project assumes you have gcloud and helm installed locally.

This project assumes the use of automated deployments, so a service account is used to apply the Terraform. Grant the service account (terraform-sa) the roles of Compute Network Admin, Editor, and Security Admin. Download the JSON credentials and set the credentials_file_path in terraform.tfvars. Alternatively, you can run this Terraform code locally with your Google account and authenticate using the gcloud CLI.

This project sets the DNS records for the Mastodon instance. The domain name must be pointed to Google Cloud DNS name servers and the service account (or Google account running the Terraform) must be an owner for the domain name in the Google Search Console.

Create a Cloud Storage bucket dedicated to storing the Terraform state. This must be provisioned manually or independently of these modules, as it is a dependency for running this Terraform.

Elastic Cloud’s Elasticsearch Service (ESS) is used because GCP does not offer managed Elasticsearch. Generate an API key to use. Blocked by Mastodon chart issue

Project structure

Terraform best practices dictate Kubernetes clusters and Kubernetes resources not co-exist. The dependencies module must be applied before and separately from the mastodon module.

The dependencies Terraform module provisions GCP-managed resources and Google Kubernetes Engine in autopilot mode.

The mastodon Terraform module deploys the official Mastodon Helm chart with GCP-specific amendments.

Run terraform init in both module directories.

Create the infrastructure

1. Create a terraform.tfvars file in ./dependencies/ with the necessary variables. See the dependencies/terraform.tfvars.example file for guidance.

2. cd ./dependencies && terraform apply

Deploy Mastodon and GKE resources

1. Clone the Mastodon Helm chart into ./charts because it is not published anywhere yet. cd ./charts && git clone https://github.com/mastodon/chart.git --single-branch --branch=main --depth=1 && cd chart && helm dep update

2. Create a terraform.tfvars file in ./mastodon/ with the necessary variables. See the mastodon/terraform.tfvars.example file for guidance.

3. cd ./mastodon && terraform apply

Known limitations

• As of 2023-06, Google Cloud's IPv6 support is a work in progress. IPv6 support will be added once GCP resolves several outstanding issues with its Terraform provider.

• WEB_DOMAIN is not supported, but could be. Contribution welcomed.

Troubleshooting

HTTPS

If you get HTTPS-related errors, but everything else seems ok, check the status of the certificate with kubectl get ManagedCertificate mastodon-cert -n mastodon. Provisioning a Google-managed certificate can take up to an hour.

Upgrading to Mastodon 4.3

You must generate encryption secrets environment variables before upgrading.

1. kubectl -n mastodon get pods to list the pods. Look for something with "mastodon-web".
2. kubectl -n mastodon exec --stdin --tty mastodon-web-99z999z9z9-99zz9 -- /bin/bash to connect to the container.
3. bin/rails db:encryption:init to generate the new encryption secrets environment variables.
4. Add the credentials to your terraform.tfvars file as active_record_encryption_primary_key, active_record_encryption_deterministic_key, and active_record_encryption_key_derivation_salt.

License

This is configuration code. This work is marked with CC0 1.0 Universal. It is dedicated to the public domain. See LICENSE file.

Contributions welcomed.