Recycling gunicorn worker (#800)

* add recycling feature to gunicorn worker

* add unit tests

* add more unit tests, and remove redundant trigger_events call

* fixed up unit tests

* make flake8 happy

* address feedbacks

* make flake8 happy

* add doc

sanic/server.py

@@ -75,7 +75,7 @@ class HttpProtocol(asyncio.Protocol):
                  signal=Signal(), connections=set(), request_timeout=60,
                  request_max_size=None, request_class=None, has_log=True,
                  keep_alive=True, is_request_stream=False, router=None,
-                 **kwargs):
+                 state=None, **kwargs):
         self.loop = loop
         self.transport = None
         self.request = None
@@ -99,6 +99,9 @@ class HttpProtocol(asyncio.Protocol):
         self._request_handler_task = None
         self._request_stream_task = None
         self._keep_alive = keep_alive
+        self.state = state if state else {}
+        if 'requests_count' not in self.state:
+            self.state['requests_count'] = 0
 
     @property
     def keep_alive(self):
@@ -154,6 +157,9 @@ class HttpProtocol(asyncio.Protocol):
             self.headers = []
             self.parser = HttpRequestParser(self)
 
+        # requests count
+        self.state['requests_count'] = self.state['requests_count'] + 1
+
         # Parse request chunk or close connection
         try:
             self.parser.feed_data(data)
@@ -389,7 +395,7 @@ def serve(host, port, request_handler, error_handler, before_start=None,
           register_sys_signals=True, run_async=False, connections=None,
           signal=Signal(), request_class=None, has_log=True, keep_alive=True,
           is_request_stream=False, router=None, websocket_max_size=None,
-          websocket_max_queue=None):
+          websocket_max_queue=None, state=None):
     """Start asynchronous HTTP Server on an individual process.
 
     :param host: Address to host on
@@ -427,8 +433,6 @@ def serve(host, port, request_handler, error_handler, before_start=None,
     if debug:
         loop.set_debug(debug)
 
-    trigger_events(before_start, loop)
-
     connections = connections if connections is not None else set()
     server = partial(
         protocol,
@@ -445,7 +449,8 @@ def serve(host, port, request_handler, error_handler, before_start=None,
         is_request_stream=is_request_stream,
         router=router,
         websocket_max_size=websocket_max_size,
-        websocket_max_queue=websocket_max_queue
+        websocket_max_queue=websocket_max_queue,
+        state=state
     )
 
     server_coroutine = loop.create_server(
@@ -457,6 +462,7 @@ def serve(host, port, request_handler, error_handler, before_start=None,
         sock=sock,
         backlog=backlog
     )
+
     # Instead of pulling time at the end of every request,
     # pull it once per minute
     loop.call_soon(partial(update_current_time, loop))
@@ -464,6 +470,8 @@ def serve(host, port, request_handler, error_handler, before_start=None,
     if run_async:
         return server_coroutine
 
+    trigger_events(before_start, loop)
+
     try:
         http_server = loop.run_until_complete(server_coroutine)
     except: