Allow restarting pool

The implementation of shutdown from
#27 does not actually
provide for a way for the pool to re-create connections, only render the
pool unusable. This implements such a behavior. A new method is added so
as to not change the existing behavior of `shutdown`.

lib/connection_pool.rb

@@ -99,6 +99,10 @@ def shutdown(&block)
     @available.shutdown(&block)
   end
 
+  def restart(&block)
+    @available.restart(&block)
+  end
+
   # Size of this connection pool
   attr_reader :size
 

lib/connection_pool/timed_stack.rb

@@ -95,6 +95,17 @@ def shutdown(&block)
     end
   end
 
+  ##
+  # Like +shutdown+, but will allow the pool to re-create connections
+  # afterwards.
+
+  def restart(&block)
+    raise ArgumentError, "restart must receive a block" unless block_given?
+
+    shutdown(&block)
+    @shutdown_block = nil
+  end
+
   ##
   # Returns +true+ if there are no available connections.
 
@@ -143,6 +154,7 @@ def shutdown_connections(options = nil)
       conn = fetch_connection(options)
       @shutdown_block.call(conn)
     end
+    @created = 0
   end
 
   ##

test/test_connection_pool_timed_stack.rb

@@ -102,6 +102,16 @@ def test_pop_shutdown
     end
   end
 
+  def test_pop_restart
+    stack = ConnectionPool::TimedStack.new(1) { Object.new }
+    object = stack.pop
+    stack.push(object)
+
+    stack.restart {}
+
+    refute_equal object, stack.pop
+  end
+
   def test_push
     stack = ConnectionPool::TimedStack.new(1) { Object.new }