BUGFIX: fix redirect, correct multisite

app/controllers/user_avatars_controller.rb

@@ -23,13 +23,13 @@ class UserAvatarsController < ApplicationController
   def show
     # we need multisite support to keep a single origin pull for CDNs
     RailsMultisite::ConnectionManagement.with_hostname(params[:hostname]) do
-      show_in_site
+      show_in_site(RailsMultisite::ConnectionManagement.current_hostname)
     end
   end
 
   protected
 
-  def show_in_site
+  def show_in_site(hostname)
     username = params[:username].to_s
     return render_dot unless user = User.find_by(username_lower: username.downcase)
 
@@ -47,7 +47,7 @@ class UserAvatarsController < ApplicationController
     upload ||= user.uploaded_avatar if user.uploaded_avatar_id == version
 
     if user.uploaded_avatar && !upload
-      return redirect_to "/avatar/#{user.username_lower}/#{size}/#{user.uploaded_avatar_id}.png"
+      return redirect_to "/avatar/#{hostname}/#{user.username_lower}/#{size}/#{user.uploaded_avatar_id}.png"
     elsif upload
       original = Discourse.store.path_for(upload)
       if Discourse.store.external? || File.exists?(original)

vendor/gems/rails_multisite/lib/rails_multisite/connection_management.rb

@@ -48,13 +48,13 @@ module RailsMultisite
       old = current_hostname
       connected = ActiveRecord::Base.connection_pool.connected?
 
-      establish_connection(:hostname => hostname) unless connected && hostname == old
+      establish_connection(:host => hostname) unless connected && hostname == old
       rval = yield hostname
 
       unless connected && hostname == old
         ActiveRecord::Base.connection_handler.clear_active_connections!
 
-        establish_connection(:hostname => old)
+        establish_connection(:host => old)
         ActiveRecord::Base.connection_handler.clear_active_connections! unless connected
       end