Eager load modules on boot

Using ActiveModelSerializers with a threaded web server eg. Puma
uninitialized constant errors are thrown. Leaving this article for
reference:
http://blog.plataformatec.com.br/2012/08/eager-loading-for-greater-good/.

lib/active_model/serializer.rb

@@ -18,16 +18,18 @@ module ActiveModel
     # @see #serializable_hash for more details on these valid keys.
     SERIALIZABLE_HASH_VALID_KEYS = [:only, :except, :methods, :include, :root].freeze
     extend ActiveSupport::Autoload
-    autoload :Adapter
-    autoload :Null
-    autoload :Attribute
-    autoload :Association
-    autoload :Reflection
-    autoload :SingularReflection
-    autoload :CollectionReflection
-    autoload :BelongsToReflection
-    autoload :HasOneReflection
-    autoload :HasManyReflection
+    eager_autoload do
+      autoload :Adapter
+      autoload :Null
+      autoload :Attribute
+      autoload :Association
+      autoload :Reflection
+      autoload :SingularReflection
+      autoload :CollectionReflection
+      autoload :BelongsToReflection
+      autoload :HasOneReflection
+      autoload :HasManyReflection
+    end
     include ActiveSupport::Configurable
     include Caching
 

lib/active_model_serializers.rb

@@ -5,16 +5,19 @@ require 'active_support/core_ext/string/inflections'
 require 'active_support/json'
 module ActiveModelSerializers
   extend ActiveSupport::Autoload
-  autoload :Model
-  autoload :Callbacks
-  autoload :Deserialization
-  autoload :SerializableResource
-  autoload :Logging
-  autoload :Test
-  autoload :Adapter
-  autoload :JsonPointer
-  autoload :Deprecate
-  autoload :LookupChain
+  eager_autoload do
+    autoload :Model
+    autoload :Callbacks
+    autoload :SerializableResource
+    autoload :SerializationContext
+    autoload :Logging
+    autoload :Test
+    autoload :Adapter
+    autoload :JsonPointer
+    autoload :Deprecate
+    autoload :LookupChain
+    autoload :Deserialization
+  end
 
   class << self; attr_accessor :logger; end
   self.logger = ActiveSupport::TaggedLogging.new(ActiveSupport::Logger.new(STDOUT))
@@ -46,6 +49,11 @@ module ActiveModelSerializers
     $VERBOSE = original_verbose
   end
 
+  def self.eager_load!
+    super
+    ActiveModel::Serializer.eager_load!
+  end
+
   require 'active_model/serializer/version'
   require 'active_model/serializer'
   require 'active_model/serializable_resource'

lib/active_model_serializers/adapter/json_api.rb

@@ -22,14 +22,16 @@ module ActiveModelSerializers
   module Adapter
     class JsonApi < Base
       extend ActiveSupport::Autoload
-      autoload :Jsonapi
-      autoload :ResourceIdentifier
-      autoload :Relationship
-      autoload :Link
-      autoload :PaginationLinks
-      autoload :Meta
-      autoload :Error
-      autoload :Deserialization
+      eager_autoload do
+        autoload :Jsonapi
+        autoload :ResourceIdentifier
+        autoload :Link
+        autoload :PaginationLinks
+        autoload :Meta
+        autoload :Error
+        autoload :Deserialization
+        autoload :Relationship
+      end
 
       def self.default_key_transform
         :dash

lib/active_model_serializers/railtie.rb

@@ -5,6 +5,8 @@ require 'action_controller/serialization'
 
 module ActiveModelSerializers
   class Railtie < Rails::Railtie
+    config.eager_load_namespaces << ActiveModelSerializers
+
     config.to_prepare do
       ActiveModel::Serializer.serializers_cache.clear
     end