BUGFIX: Correct after_fork semantics

After fork SiteSettings was not getting a new process id,
causing site settings not to refresh properly in unicorn

This code also centralizes the logic

config/initializers/01-redis.rb

@@ -10,10 +10,7 @@ end
 if defined?(PhusionPassenger)
     PhusionPassenger.on_event(:starting_worker_process) do |forked|
         if forked
-            # We're in smart spawning mode.
-            $redis = DiscourseRedis.new
-            Discourse::Application.config.cache_store.reconnect
-            MessageBus.after_fork
+            Discourse.after_fork
         else
             # We're in conservative spawning mode. We don't need to do anything.
         end

config/spring.rb

@@ -6,8 +6,6 @@
 # spring binstub rake
 # spring binstub rspec
 Spring.after_fork do
-  $redis.client.reconnect
-  Rails.cache.reconnect
-  MessageBus.after_fork
+  Discourse.after_fork
 end
 Spring::Commands::Rake.environment_matchers["spec"] = "test"

config/unicorn.conf.rb

@@ -83,8 +83,5 @@ before_fork do |server, worker|
 end
 
 after_fork do |server, worker|
-  ActiveRecord::Base.establish_connection
-  $redis.client.reconnect
-  Rails.cache.reconnect
-  MessageBus.after_fork
+  Discourse.after_fork
 end

lib/backup_restore.rb

@@ -174,14 +174,7 @@ module BackupRestore
   end
 
   def self.after_fork
-    # reconnect to redis
-    $redis.client.reconnect
-    # reconnect the rails cache (uses redis)
-    Rails.cache.reconnect
-    # tells the message we've forked
-    MessageBus.after_fork
-    # /!\ HACK /!\ force sidekiq to create a new connection to redis
-    Sidekiq.instance_variable_set(:@redis, nil)
+    Discourse.after_fork
   end
 
   def self.backup_tables_count

lib/demon/base.rb

@@ -118,11 +118,7 @@ class Demon::Base
   end
 
   def establish_app
-    ActiveRecord::Base.connection_handler.clear_active_connections!
-    ActiveRecord::Base.establish_connection
-    $redis.client.reconnect
-    Rails.cache.reconnect
-    MessageBus.after_fork
+    Discourse.after_fork
 
     Signal.trap("HUP") do
       begin

lib/discourse.rb

@@ -234,4 +234,17 @@ module Discourse
     "/site/read-only"
   end
 
+  # all forking servers must call this
+  # after fork, otherwise Discourse will be
+  # in a bad state
+  def self.after_fork
+    SiteSetting.after_fork
+    ActiveRecord::Base.establish_connection
+    $redis.client.reconnect
+    Rails.cache.reconnect
+    MessageBus.after_fork
+    # /!\ HACK /!\ force sidekiq to create a new connection to redis
+    Sidekiq.instance_variable_set(:@redis, nil)
+  end
+
 end

lib/site_setting_extension.rb

@@ -179,6 +179,10 @@ module SiteSettingExtension
     @@process_id ||= SecureRandom.uuid
   end
 
+  def after_fork
+    @@process_id = nil
+  end
+
   def remove_override!(name)
     provider.destroy(name)
     current[name] = defaults[name]

spec/spec_helper.rb

@@ -98,9 +98,7 @@ end
 
 Spork.each_run do
   # This code will be run each time you run your specs.
-  $redis.client.reconnect
-  Rails.cache.reconnect
-  MessageBus.after_fork
+  Discourse.after_fork
 end
 
 # --- Instructions ---