Delay initialization until Rails is fully initialized

README.md

@@ -14,6 +14,26 @@ Useful for:
 *NOTE:* As of 1.0.6 works with Sidekiq 4.
 *NOTE:* As of 1.0.8 Locking is atomic (set nx/ex) and will no longer lead to batches that are permalocked and stuck
 
+## Installation
+
+Add this line to your application's Gemfile:
+
+    gem 'sidekiq-grouping'
+
+And then execute:
+
+    $ bundle
+
+Or install it yourself as:
+
+    $ gem install sidekiq-grouping
+
+If you're using the gem outside of Rails, run Grouping when application is initialized:
+
+```ruby
+Sidekiq::Grouping.start! if Sidekiq.server?
+```
+
 ## Usage
 
 Create a worker:
@@ -195,20 +215,6 @@ end
 
 ```
 
-## Installation
-
-Add this line to your application's Gemfile:
-
-    gem 'sidekiq-grouping'
-
-And then execute:
-
-    $ bundle
-
-Or install it yourself as:
-
-    $ gem install sidekiq-grouping
-
 ## Contributing
 
 1. Fork it ( http://github.com/gzigzigzeo/sidekiq-grouping/fork )

lib/sidekiq/grouping.rb

@@ -3,6 +3,7 @@
 require "active_support/core_ext/numeric/time"
 require "sidekiq/grouping/version"
 require "concurrent"
+require "sidekiq/grouping/railtie" if defined?(Rails)
 
 module Sidekiq::Grouping
   autoload :Config, "sidekiq/grouping/config"
@@ -50,4 +51,3 @@ def start!
   end
 end
 
-Sidekiq::Grouping.start! if Sidekiq.server?

lib/sidekiq/grouping/railtie.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Sidekiq
+  module Grouping
+    class Railtie < ::Rails::Railtie
+      config.after_initialize do
+        Sidekiq::Grouping.start! if Sidekiq.server?
+      end
+    end
+  end
+end