Source Code

Our goal is to provide the best possible Mastodon experience for our members. One way to deliver on that is by delivering the most up-to-date Mastodon code. We "run off main", which means using the latest commits to the main branch of the Mastodon codebase found on the project's official GitHub repository.

We take a clean copy of the latest Mastodon code and then apply a limited set of modification with a custom script. We then build the modified code inside a Docker container, publish it to GitHub and Docker Hub, for consumption by our Kubernetes cluster.

Mastodon instance specific customizations include:

Container specific build settings include:

  • Using Docker 12 "Bookworm" with the latest package updates as our container base operating system
  • Enabling YJIT for better Ruby performance
  • Performance optimizations for Jemalloc.

We intend to upstream these changes with the adoption of PR mastodon/mastodon #26850 to the Mastodon project, or a similar concept.

Container Availability

Our customized container image is available from both Docker and GitHub container registries.

Streaming Container

Our default container removes Node.js and is not able to run the Mastodon Streaming API, but we have a customized container image specific to this task which is stripped down and based on Debian, available from both Docker and GitHub container registries.

Redis TLS Changes

Digital Ocean requires encrypted/TLS connections to their managed Redis instances, however the Mastodon codebase uses a Redis driver (hiredis) which does not have a native TLS capability. To accommodate this, we have in the past used HAProxy or Stunnel to take the un-encrypted connection requests and encrypt those connections between the Mastodon components and Redis.

We have chosen to remove the hiredis driver from our installation and use redis-rb instead. Using the native redis-rb driver provides support for TLS connections. This is done by patching a stock Mastodon installation with the following commands, downloading updated bundles and node components, and recompiling:

sed -i '/gem '\''hiredis'\'', '\''~> 0.6'\''/d' ./Gemfile
sed -i '/hiredis/d' ./Gemfile.lock
sed -i '/hiredis/d' ./lib/mastodon/redis_config.rb
sed -i '/hiredis/d' ./lib/tasks/mastodon.rake
sed -i 's/, driver: :hiredis//g' ./app/lib/redis_configuration.rb
sed -i 's/, require: \['\''redis'\'', '\''redis\/connection\/hiredis'\''\]//' ./Gemfile

Compared to running with hiredis through HAProxy or Stunnel, we have not seen any negative impact in performance by using redis-rb.

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