Report request size

kinto/core/initialization.py

@@ -491,6 +491,13 @@ def on_new_response(event):
             ],
         )
 
+        # Observe response size.
+        metrics_service.observe(
+            "request_size",
+            len(request.response.body or b""),
+            labels=[("endpoint", utils.strip_uri_prefix(request.path))],
+        )
+
         # Count authentication verifications.
         if hasattr(request, "authn_type"):
             metrics_service.count(f"authn_type.{request.authn_type}")

kinto/core/metrics.py

@@ -16,6 +16,11 @@ def timer(key):
         Watch execution time.
         """
 
+    def observe(self, key, value, labels=[]):
+        """
+        Observe a give `value` for the specified `key`.
+        """
+
     def count(key, count=1, unique=None):
         """
         Count occurrences. If `unique` is set, overwrites the counter value

kinto/plugins/prometheus.py

@@ -89,6 +89,28 @@ def timer(self, key):
 
         return Timer(_METRICS[key])
 
+    def observe(self, key, value, labels=[]):
+        global _METRICS
+
+        if key not in _METRICS:
+            _METRICS[key] = prometheus_module.Summary(
+                _fix_metric_name(key),
+                f"Summary of {key}",
+                labelnames=[label_name for label_name, _ in labels],
+                registry=get_registry(),
+            )
+
+        if not isinstance(_METRICS[key], prometheus_module.Summary):
+            raise RuntimeError(
+                f"Metric {key} already exists with different type ({_METRICS[key]})"
+            )
+
+        m = _METRICS[key]
+        if labels:
+            m = m.labels(*(label_value for _, label_value in labels))
+
+        m.observe(value)
+
     def count(self, key, count=1, unique=None):
         global _METRICS
 

kinto/plugins/statsd.py

@@ -21,6 +21,9 @@ def __init__(self, host, port, prefix):
     def timer(self, key):
         return self._client.timer(key)
 
+    def observe(self, key, value, labels=[]):
+        return self._client.gauge(key, value)
+
     def count(self, key, count=1, unique=None):
         if unique is None:
             return self._client.incr(key, count=count)

tests/core/test_initialization.py

@@ -413,6 +413,16 @@ def test_statsd_counts_endpoints(self):
             unique=[("method", "get"), ("endpoint", "/__heartbeat__"), ("status", "200")],
         )
 
+    def test_statsd_observe_request_size(self):
+        kinto.core.initialize(self.config, "0.0.1", "settings_prefix")
+        app = webtest.TestApp(self.config.make_wsgi_app())
+        app.get("/v0/__heartbeat__")
+        self.mocked().observe.assert_any_call(
+            "request_size",
+            len("{}"),
+            labels=[("endpoint", "/__heartbeat__")],
+        )
+
     def test_statsd_counts_views_and_methods(self):
         kinto.core.initialize(self.config, "0.0.1", "settings_prefix")
         app = webtest.TestApp(self.config.make_wsgi_app())

tests/plugins/test_prometheus.py

@@ -78,6 +78,18 @@ def test_timer_can_be_used_as_decorator_on_partial_function(self):
         resp = self.app.get("/__metrics__")
         self.assertIn("TYPE func_latency_partial summary", resp.text)
 
+    def test_observe_a_single_value(self):
+        self.app.app.registry.metrics.observe("price", 111)
+
+        resp = self.app.get("/__metrics__")
+        self.assertIn("price_sum 111", resp.text)
+
+    def test_observe_a_single_value_with_labels(self):
+        self.app.app.registry.metrics.observe("size", 3.14, labels=[("endpoint", "/buckets")])
+
+        resp = self.app.get("/__metrics__")
+        self.assertIn('size_sum{endpoint="/buckets"} 3.14', resp.text)
+
     def test_count_by_key(self):
         self.app.app.registry.metrics.count("key")
 
@@ -107,6 +119,10 @@ def test_metrics_cant_be_mixed(self):
         with self.assertRaises(RuntimeError):
             self.app.app.registry.metrics.count("timer")
 
+        self.app.app.registry.metrics.count("observer")
+        with self.assertRaises(RuntimeError):
+            self.app.app.registry.metrics.observe("observer", 42)
+
     def test_metrics_names_and_labels_are_transformed(self):
         self.app.app.registry.metrics.count("http.home.status", unique=[("code.get", "200")])
 

tests/plugins/test_statsd.py

@@ -31,6 +31,11 @@ def setUp(self):
         self.mocked_client = patch.start()
         self.addCleanup(patch.stop)
 
+    def test_observe_a_single_value(self):
+        with mock.patch.object(self.client, "_client") as mocked_client:
+            self.client.observe("size", 3.14)
+            mocked_client.gauge.assert_called_with("size", 3.14)
+
     def test_count_increments_the_counter_for_key(self):
         with mock.patch.object(self.client, "_client") as mocked_client:
             self.client.count("click")