discourse/config/initializers/200-first_middlewares.rb

# frozen_string_literal: true

# we want MessageBus to be close to the front
# this is important cause the vast majority of web requests go to it
# this allows us to avoid full middleware crawls each time
#
# We aren't manipulating the middleware stack directly because of
# https://github.com/rails/rails/pull/27936

Rails.configuration.middleware.unshift(MessageBus::Rack::Middleware)

# no reason to track this in development, that is 300+ redis calls saved per
# page view (we serve all assets out of thin in development)
if Rails.env != "development" || ENV["TRACK_REQUESTS"]
  require "middleware/request_tracker"
  Rails.configuration.middleware.unshift Middleware::RequestTracker

  MethodProfiler.ensure_discourse_instrumentation! if GlobalSetting.enable_performance_http_headers
end

if Rails.env.test?
  # In test mode we can't insert/remove middlewares
  # Therefore we insert a small helper which effectively switches the multisite
  # middleware on/off based on the Rails.configuration.multisite value
  class TestMultisiteMiddleware < RailsMultisite::Middleware
    def call(env)
      return @app.call(env) if !Rails.configuration.multisite
      super(env)
    end
  end

  Rails.configuration.middleware.unshift TestMultisiteMiddleware,
                                         RailsMultisite::DiscoursePatches.config

  class BlockRequestsMiddleware
    @@block_requests = false

    def self.block_requests!
      @@block_requests = true
    end

    def self.allow_requests!
      @@block_requests = false
    end

    def initialize(app)
      @app = app
    end

    def call(env)
      if @@block_requests
        [503, { "Content-Type" => "text/plain" }, ["Blocked by BlockRequestsMiddleware"]]
      else
        @app.call(env)
      end
    end
  end

  Rails.configuration.middleware.unshift BlockRequestsMiddleware
elsif Rails.configuration.multisite
  assets_hostnames = GlobalSetting.cdn_hostnames

  if assets_hostnames.empty?
    assets_hostnames = Discourse::Application.config.database_configuration[Rails.env]["host_names"]
  end

  RailsMultisite::ConnectionManagement.asset_hostnames = assets_hostnames

  # Multisite needs to be first, because the request tracker and message bus rely on it
  Rails.configuration.middleware.unshift RailsMultisite::Middleware,
                                         RailsMultisite::DiscoursePatches.config
  Rails.configuration.middleware.delete ActionDispatch::Executor

  if defined?(RailsFailover::ActiveRecord) && Rails.configuration.active_record_rails_failover
    Rails.configuration.middleware.insert_after(
      RailsMultisite::Middleware,
      RailsFailover::ActiveRecord::Middleware,
    )
  end

  if Rails.env.development?
    # Automatically allow development multisite hosts
    RailsMultisite::ConnectionManagement.instance.db_spec_cache.each do |db, specification|
      next if db == "default"
      Rails.configuration.hosts.concat(specification.spec.configuration_hash[:host_names])
    end
  end
elsif defined?(RailsFailover::ActiveRecord) && Rails.configuration.active_record_rails_failover
  Rails.configuration.middleware.insert_before(
    MessageBus::Rack::Middleware,
    RailsFailover::ActiveRecord::Middleware,
  )
end