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

@@ -104,6 +104,15 @@ def shutdown(&block)
     @available.shutdown(&block)
   end
 
+  ##
+  # Reloads the ConnectionPool by passing each connection to +block+ and then
+  # removing it the pool. Subsequent checkouts will create new connections as
+  # needed.
+
+  def reload(&block)
+    @available.shutdown(reload: true, &block)
+  end
+
   # Size of this connection pool
   attr_reader :size
 

lib/connection_pool/timed_stack.rb

@@ -83,16 +83,18 @@ def pop(timeout = 0.5, options = {})
   ##
   # Shuts down the TimedStack by passing each connection to +block+ and then
   # removing it from the pool. Attempting to checkout a connection after
-  # shutdown will raise +ConnectionPool::PoolShuttingDownError+.
+  # shutdown will raise +ConnectionPool::PoolShuttingDownError+ unless
+  # +:reload+ is +true+.
 
-  def shutdown(&block)
+  def shutdown(reload: false, &block)
     raise ArgumentError, "shutdown must receive a block" unless block_given?
 
     @mutex.synchronize do
       @shutdown_block = block
       @resource.broadcast
 
       shutdown_connections
+      @shutdown_block = nil if reload
     end
   end
 
@@ -144,6 +146,7 @@ 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_shutdown_reload
+    stack = ConnectionPool::TimedStack.new(1) { Object.new }
+    object = stack.pop
+    stack.push(object)
+
+    stack.shutdown(reload: true) {}
+
+    refute_equal object, stack.pop
+  end
+
   def test_push
     stack = ConnectionPool::TimedStack.new(1) { Object.new }