Welcome to the Discourse Codebase

Chapter I

Discourse is a Ruby on Rails backend paired with an Ember.js single-page frontend (now living under frontend/discourse in a pnpm workspace). The Rails side exposes a JSON API through controllers, ActiveRecord models, and serializers, while the Ember app consumes that JSON and re-hydrates it into its own client-side models. A first-class plugin system (plugins/*) and a MessageBus-based real-time layer let both official features and third-party plugins extend or react to almost anything in the system.

Discourse Request & Data Flow

Plugin Systemlib/plugin/instance.rb

Rails Controllers…rollers/application_controller.rb

ActiveRecord Modelsapp/models/topic.rb

JSON Serializersapp/serializers/post_serializer.rb

Ember.js Frontendfrontend/discourse/app/app.js

Sidekiq Background Jobsapp/jobs/base.rb

MessageBus Realtime Layerlib/discourse_event.rb

Figure I · Click a node to see what it does, where it lives in the code, and its labeled connections — the annotation opens beside it.