Signaling support with Blinker integration

docs/signals.md

@@ -0,0 +1,27 @@
+# Signals
+
+Signals allow you to send notifications to multiple subscribers when the specific event occured.
+Signaling is provided by [Blinker](http://pythonhosted.org/blinker/) library and
+Sanic has few built-in signals:
+
+* `request_started`: Sent when the request processing has started.
+* `request_finished`: Sent when the request processing has finished.
+
+## Examples
+
+```python
+from sanic.signals import request_started
+import my_realtime_stat
+
+app = Sanic(__name__)
+
+@request_started.connect
+def collect_stats(request):
+    my_realtime_stat.incoming_requests.incr(request.url)
+
+
+@request_finished.connect
+def count_errors(response):
+    if response.status != 200:
+        my_realtime_stat.error_responses.incr(response.status)
+```

requirements.txt

@@ -2,3 +2,5 @@ httptools
 ujson
 uvloop
 aiofiles
+multidict
+blinker

sanic/sanic.py

@@ -13,6 +13,7 @@ from .log import log
 from .response import HTTPResponse
 from .router import Router
 from .server import serve, HttpProtocol
+from .signals import request_started, request_finished
 from .static import register as static_register
 from .exceptions import ServerError
 from socket import socket, SOL_SOCKET, SO_REUSEADDR
@@ -176,6 +177,8 @@ class Sanic:
         :return: Nothing
         """
         try:
+            request_started.send(request)
+
             # -------------------------------------------- #
             # Request Middleware
             # -------------------------------------------- #
@@ -239,6 +242,7 @@ class Sanic:
                     response = HTTPResponse(
                         "An error occurred while handling an error")
 
+        request_finished.send(response)
         response_callback(response)
 
     # -------------------------------------------------------------------- #

sanic/signals.py

@@ -0,0 +1,10 @@
+from blinker import Namespace
+
+__all__ = ('request_started', 'request_finished')
+
+_signals = Namespace()
+signal = _signals.signal
+
+
+request_started = signal('request-started')
+request_finished = signal('request-finished')