Fix observation of status codes

This should now cover all cases where the request is even routed
to an endpoint. Note that this still does not catch
`405 Method not allowed` errors because those aren’t even routed to
an endpoint.

muchopper/web/__init__.py

@@ -259,17 +259,31 @@ def render_static_template(path):
                           "text/html")
 
 
-def collect_status(metric):
+def observe(app):
+    status_metric = PROMETHEUS_METRIC_STATUS_CODE
+
     def wrapper(f):
+        endpoint = f.__name__
         @functools.wraps(f)
         def wrapped(*args, **kwargs):
-            result = f(*args, **kwargs)
-            if not isinstance(result, werkzeug.BaseResponse):
-                result = make_response(result)
+            status_code = 500
+            try:
+                try:
+                    result = f(*args, **kwargs)
+                except BaseException as exc:
+                    result = app.handle_user_exception(exc)
+
+                if not isinstance(result, werkzeug.BaseResponse):
+                    result = make_response(result)
 
-            metric.labels(f.__name__, str(result.status_code)).inc()
+                status_code = result.status_code
 
-            return result
+                return result
+            except BaseException as exc:
+                status_code = 500
+                raise
+            finally:
+                status_metric.labels(endpoint, str(status_code)).inc()
 
         return wrapped
     return wrapper
@@ -407,7 +421,7 @@ def ccg_rgb_triplet(s):
 
 
 @app.route("/")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def index():
     return redirect(url_for("room_list", pageno=1))
 
@@ -434,7 +448,7 @@ def room_page(page, per_page, **kwargs):
 @app.route("/rooms/")
 @app.route("/rooms/<int:pageno>")
 @register_menu(app, "data.rooms", "All Rooms", order=1)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 @PROMETHEUS_METRIC_ROOM_PAGE_HTML.time()
 def room_list(pageno=1):
     per_page = 25
@@ -460,7 +474,7 @@ def room_list(pageno=1):
 
 
 @app.route("/avatar/v1/<address>")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def avatar_v1(address):
     try:
         address = aioxmpp.JID.fromstr(address)
@@ -500,7 +514,7 @@ def avatar_v1(address):
 
 @app.route("/search")
 @register_menu(app, "data.search", "Search", order=2)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 @PROMETHEUS_METRIC_SEARCH_HTML.time()
 def search():
     no_keywords = False
@@ -613,7 +627,7 @@ def get_metrics():
 
 @app.route("/stats")
 @register_menu(app, "data.stats", "Statistics", order=4)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 @PROMETHEUS_METRIC_STATS_HTML.time()
 def statistics():
     common_metrics = get_metrics()
@@ -701,62 +715,62 @@ def statistics():
 
 @app.route("/docs/faq")
 @register_menu(app, "docs.faq", "Frequent Questions (FAQ)", order=1)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def faq():
     return render_static_template("faq.html")
 
 
 @app.route("/docs/owners")
 @register_menu(app, "docs.owners", "For room owners", order=2)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def owners():
     return render_static_template("for_owners.html")
 
 
 @app.route("/docs/operators")
 @register_menu(app, "docs.operators", "For service operators", order=3)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def operators():
     return render_static_template("for_operators.html")
 
 
 @app.route("/docs/api")
 @register_menu(app, "docs.developers", "For developers", order=4)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def developers():
     return render_static_template("for_developers.html")
 
 
 @app.route("/about")
 @register_menu(app, "meta.about", "About", order=1)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def about():
     return render_static_template("about.html")
 
 
 @app.route("/tos")
 @register_menu(app, "meta.tos", "Terms of Service", order=2)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def tos():
     return render_static_template("tos.html")
 
 
 @app.route("/privacy")
 @register_menu(app, "meta.privacy", "Privacy Policy", order=3)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def privacy():
     return render_static_template("privacy.html")
 
 
 @app.route("/legal")
 @register_menu(app, "meta.legal", "Legal notes & Contact", order=4)
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def legal():
     return render_static_template("legal.html")
 
 
 @app.route("/contact")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def contact():
     return redirect(url_for('legal'))
 
@@ -780,7 +794,7 @@ def room_to_json(muc, public_info):
 
 @app.route("/api/1.0/rooms.json")
 @app.route("/api/1.0/rooms/unsafe")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 @PROMETHEUS_METRIC_ROOM_PAGE_UNSAFE_API.time()
 def api_rooms_unsafe():
     try:
@@ -822,7 +836,7 @@ def optional_typecast_argument(args, name, type_):
 
 
 @app.route("/api/1.0/rooms")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 @PROMETHEUS_METRIC_ROOM_PAGE_API.time()
 def api_rooms_safe():
     PAGE_SIZE = 200
@@ -865,7 +879,7 @@ def api_rooms_safe():
 
 
 @app.route("/api/1.0/search", methods=["POST", "GET"])
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 @PROMETHEUS_METRIC_SEARCH_API.time()
 def api_search():
     payload = request.get_json()
@@ -992,7 +1006,7 @@ def api_search():
 
 
 @app.route("/api/1.0/badge")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 @PROMETHEUS_METRIC_BADGE_API.time()
 def api_badge():
     CHARWIDTH = 7
@@ -1080,7 +1094,7 @@ def collect(self):
 
 
 @app.route("/metrics")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def metrics():
     return Response(
         prometheus_client.exposition.generate_latest(),
@@ -1089,7 +1103,7 @@ def metrics():
 
 
 @app.route("/site.webmanifest")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def site_manifest():
     # this is needed for icons
     generator = functools.partial(
@@ -1121,7 +1135,7 @@ def site_manifest():
 
 
 @app.route("/favicon.ico")
-@collect_status(PROMETHEUS_METRIC_STATUS_CODE)
+@observe(app)
 def favicon():
     # fallback resource
     return app.send_static_file('img/favicon.ico')