Lazily enable mysql gaplock protection (#402)

lib/statesman.rb

@@ -20,19 +20,25 @@ module Adapters
   # Example:
   #   Statesman.configure do
   #     storage_adapter Statesman::ActiveRecordAdapter
+  #     enable_mysql_gaplock_protection
   #   end
   #
   def self.configure(&block)
-    config = Config.new(block)
+    @config = Config.new(block)
     @storage_adapter = config.adapter_class
-    @mysql_gaplock_protection = config.mysql_gaplock_protection
   end
 
   def self.storage_adapter
     @storage_adapter || Adapters::Memory
   end
 
   def self.mysql_gaplock_protection?
-    @mysql_gaplock_protection
+    return @mysql_gaplock_protection unless @mysql_gaplock_protection.nil?
+
+    @mysql_gaplock_protection = config.mysql_gaplock_protection?
+  end
+
+  def self.config
+    @config ||= Config.new
   end
 end

lib/statesman/config.rb

@@ -5,18 +5,23 @@
 
 module Statesman
   class Config
-    attr_reader :adapter_class, :mysql_gaplock_protection
+    attr_reader :adapter_class
 
     def initialize(block = nil)
       instance_eval(&block) unless block.nil?
     end
 
     def storage_adapter(adapter_class)
+      @adapter_class = adapter_class
+    end
+
+    def mysql_gaplock_protection?
+      return @mysql_gaplock_protection unless @mysql_gaplock_protection.nil?
+
       # If our adapter class suggests we're using mysql, enable gaplock protection by
       # default.
       enable_mysql_gaplock_protection if mysql_adapter?(adapter_class)
-
-      @adapter_class = adapter_class
+      @mysql_gaplock_protection
     end
 
     def enable_mysql_gaplock_protection