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)
+```