Statsd counter for user agents.

We want to log the usage of the various API clients we have so that we understand when they can be cycled.

To this end we are going to count usage in statsd.

All notify clients have a suer agent, of the format: NOTIFY-API-{LANGUAGE}-CLIENT/version.number

For example, NOTIFY-API-PYTHON-CLIENT/3.0.0

We convert that into a statsd/graphite friendly string of the format: notify-api-python-client.3-0-0

So we can subdivide on client and client version on our dashboards.

Present but unknown User agents are records as "non-notify-user-agent"

Missing are presented as "unknown"

app/__init__.py

@@ -114,12 +114,17 @@ def init_app(app):
             url_for('status.show_delivery_status'),
             url_for('spec.get_spec')
         ]
+
         if request.path not in no_auth_req:
             from app.authentication import auth
             error = auth.requires_auth()
             if error:
                 return error
 
+    @app.before_request
+    def record_user_agent():
+        statsd_client.incr("user-agent.{}".format(process_user_agent(request.headers.get('User-Agent', None))))
+
     @app.before_request
     def record_request_details():
         g.start = monotonic()
@@ -141,3 +146,15 @@ def init_app(app):
 
 def create_uuid():
     return str(uuid.uuid4())
+
+
+def process_user_agent(user_agent_string):
+    if user_agent_string and user_agent_string.lower().startswith("notify"):
+        components = user_agent_string.split("/")
+        client_name = components[0].lower()
+        client_version = components[1].replace(".", "-")
+        return "{}.{}".format(client_name, client_version)
+    elif user_agent_string and not user_agent_string.lower().startswith("notify"):
+        return "non-notify-user-agent"
+    else:
+        return "unknown"