discourse/config/initializers/04-message_bus.rb

MessageBus.site_id_lookup do
  RailsMultisite::ConnectionManagement.current_db
end

MessageBus.user_id_lookup do |env|
  user = CurrentUser.lookup_from_env(env)
  user.id if user
end

MessageBus.group_ids_lookup do |env|
  user = CurrentUser.lookup_from_env(env)
  user.groups.select('groups.id').map{|g| g.id} if user
end

MessageBus.on_connect do |site_id|
  RailsMultisite::ConnectionManagement.establish_connection(db: site_id)
end

MessageBus.on_disconnect do |site_id|
  ActiveRecord::Base.connection_handler.clear_active_connections!
end

# Point at our redis
MessageBus.redis_config = YAML.load(ERB.new(File.new("#{Rails.root}/config/redis.yml").read).result)[Rails.env].symbolize_keys

MessageBus.long_polling_enabled = SiteSetting.enable_long_polling
MessageBus.long_polling_interval = SiteSetting.long_polling_interval

MessageBus.is_admin_lookup do |env|
  user = CurrentUser.lookup_from_env(env)
  if user && user.admin
    true
  else
    false
  end
end

MessageBus.cache_assets = !Rails.env.development?
MessageBus.enable_diagnostics

digest = Rails.application.assets.digest.to_s
channel = "/global/asset-version"
message = MessageBus.last_message(channel)

unless message && message.data == digest
  MessageBus.publish channel, digest
end