http_server: Stop http server safely

Signed-off-by: Shizuo Fujita <[email protected]>

lib/fluent/plugin_helper/http_server/server.rb

@@ -67,16 +67,23 @@ def start(notify = nil)
             if notify
               notify.push(:ready)
             end
+
+            if async_v2?
+              @server_task_queue = ::Thread::Queue.new
+              @server_task_queue.pop
+              @server_task&.stop
+            end
           end
 
           @logger.debug('Finished HTTP server')
         end
 
         def stop
           @logger.debug('closing HTTP server')
-
-          if @server_task
-            @server_task.stop
+          if async_v2?
+            @server_task_queue&.push(:stop)
+          else
+            @server_task&.stop
           end
         end
 
@@ -93,6 +100,10 @@ def stop
             @router.mount(name, path, app || block)
           end
         end
+
+        private def async_v2?
+          Gem::Version.new(Async::VERSION) >= Gem::Version.new('2.0')
+        end
       end
     end
   end