remove early pool initialization

Author: pitr-ch

lib/concurrent/configuration.rb

@@ -14,9 +14,9 @@ class Configuration
 
     # Create a new configuration object.
     def initialize
-      @global_task_pool = Delay.new { new_task_pool }
+      @global_task_pool      = Delay.new { new_task_pool }
       @global_operation_pool = Delay.new { new_operation_pool }
-      @global_timer_set = Delay.new { Concurrent::TimerSet.new }
+      @global_timer_set      = Delay.new { Concurrent::TimerSet.new }
     end
 
     # Global thread pool optimized for short *tasks*.
@@ -111,11 +111,6 @@ def new_operation_pool
   # @yieldparam [Configuration] the current configuration object
   def self.configure
     yield(configuration)
-
-    # initialize the global thread pools if necessary
-    configuration.global_task_pool
-    configuration.global_operation_pool
-    configuration.global_timer_set
   end
 
   private

spec/concurrent/configuration_spec.rb

@@ -24,11 +24,12 @@ module Concurrent
         Concurrent.configuration.global_task_pool.should eq executor
       end
 
-      specify 'writer raises an exception if called twice' do
+      specify 'writer raises an exception if called after initialization' do
         executor = ImmediateExecutor.new
         Concurrent.configure do |config|
           config.global_task_pool = executor
         end
+        Concurrent.configuration.global_task_pool
         expect {
           Concurrent.configure do |config|
             config.global_task_pool = executor
@@ -52,11 +53,12 @@ module Concurrent
         Concurrent.configuration.global_operation_pool.should eq executor
       end
 
-      specify 'writer raises an exception if called twice' do
+      specify 'writer raises an exception if called after initialization' do
         executor = ImmediateExecutor.new
         Concurrent.configure do |config|
           config.global_operation_pool = executor
         end
+        Concurrent.configuration.global_operation_pool
         expect {
           Concurrent.configure do |config|
             config.global_operation_pool = executor