Add WsgiInstrumentor labeler support for custom metrics

Author: tammy-baylis-swi

CHANGELOG.md

@@ -22,7 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - `opentelemetry-instrumentation-confluent-kafka` Add support for confluent-kafka <=2.11.0
   ([#3685](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3685))
-- `opentelemetry-instrumentation`, `opentelemetry-instrumentation-flask`: Add Labeler utility. Add FlaskInstrumentor support of custom attributes merging for HTTP duration metrics.
+- `opentelemetry-instrumentation`, `opentelemetry-instrumentation-flask`, `opentelemetry-instrumentation-wsgi`: Add Labeler utility. Add FlaskInstrumentor, WsgiInstrumentor support of custom attributes merging for HTTP duration metrics.
   ([#3689](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3689))
 
 ## Version 1.36.0/0.57b0 (2025-07-29)

instrumentation/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/__init__.py

@@ -79,6 +79,39 @@ def GET(self):
         )
         server.start()
 
+Custom Metrics Attributes using Labeler
+***************************************
+The WSGI instrumentation reads from a Labeler utility that supports adding custom attributes
+to the HTTP duration metrics recorded by the instrumentation.
+
+
+.. code-block:: python
+
+    from flask import Flask
+    from opentelemetry.instrumentation._labeler import get_labeler
+    from opentelemetry.instrumentation.wsgi import OpenTelemetryMiddleware
+
+    app = Flask(__name__)
+    app.wsgi_app = OpenTelemetryMiddleware(app.wsgi_app)
+
+    @app.route("/user/<user_id>")
+    def user_profile(user_id):
+        # Get the labeler for the current request
+        labeler = get_labeler()
+        # Add custom attributes to WSGI instrumentation metrics
+        labeler.add("user_id", user_id)
+        labeler.add("user_type", "registered")
+        # Or, add multiple attributes at once
+        labeler.add_attributes({
+            "feature_flag": "new_ui",
+            "experiment_group": "control"
+        })
+        return f"User profile for {user_id}"
+
+    if __name__ == "__main__":
+        app.run(debug=True)
+
+
 Configuration
 -------------
 
@@ -223,6 +256,7 @@ def response_hook(span: Span, environ: WSGIEnvironment, status: str, response_he
 from typing import TYPE_CHECKING, Any, Callable, Dict, Iterable, TypeVar, cast
 
 from opentelemetry import context, trace
+from opentelemetry.instrumentation._labeler import enhance_metric_attributes
 from opentelemetry.instrumentation._semconv import (
     HTTP_DURATION_HISTOGRAM_BUCKETS_NEW,
     _filter_semconv_active_request_count_attr,
@@ -712,13 +746,21 @@ def __call__(
                 duration_attrs_old = _parse_duration_attrs(
                     req_attrs, _StabilityMode.DEFAULT
                 )
+                # Enhance attributes with any custom labeler attributes
+                duration_attrs_old = enhance_metric_attributes(
+                    duration_attrs_old
+                )
                 self.duration_histogram_old.record(
                     max(round(duration_s * 1000), 0), duration_attrs_old
                 )
             if self.duration_histogram_new:
                 duration_attrs_new = _parse_duration_attrs(
                     req_attrs, _StabilityMode.HTTP
                 )
+                # Enhance attributes with any custom labeler attributes
+                duration_attrs_new = enhance_metric_attributes(
+                    duration_attrs_new
+                )
                 self.duration_histogram_new.record(
                     max(duration_s, 0), duration_attrs_new
                 )

instrumentation/opentelemetry-instrumentation-wsgi/tests/test_wsgi_middleware.py

@@ -22,6 +22,10 @@
 
 import opentelemetry.instrumentation.wsgi as otel_wsgi
 from opentelemetry import trace as trace_api
+from opentelemetry.instrumentation._labeler import (
+    clear_labeler,
+    get_labeler,
+)
 from opentelemetry.instrumentation._semconv import (
     HTTP_DURATION_HISTOGRAM_BUCKETS_NEW,
     OTEL_SEMCONV_STABILITY_OPT_IN,
@@ -139,6 +143,14 @@ def error_wsgi_unhandled(environ, start_response):
     raise ValueError
 
 
+def error_wsgi_unhandled_custom_attrs(environ, start_response):
+    labeler = get_labeler()
+    labeler.add("custom_attr", "test_value")
+    labeler.add_attributes({"endpoint_type": "test", "feature_flag": True})
+    assert isinstance(environ, dict)
+    raise ValueError
+
+
 def wsgi_with_custom_response_headers(environ, start_response):
     assert isinstance(environ, dict)
     start_response(
@@ -201,6 +213,28 @@ def wsgi_with_repeat_custom_response_headers(environ, start_response):
     "http.server.request.duration": _server_duration_attrs_new,
 }
 
+_custom_attributes = ["custom_attr", "endpoint_type", "feature_flag"]
+_server_duration_attrs_old_with_custom = _server_duration_attrs_old.copy()
+_server_duration_attrs_old_with_custom.append("http.target")
+_server_duration_attrs_old_with_custom.extend(_custom_attributes)
+_server_duration_attrs_new_with_custom = _server_duration_attrs_new.copy()
+_server_duration_attrs_new_with_custom.append("http.route")
+_server_duration_attrs_new_with_custom.extend(_custom_attributes)
+
+_recommended_metrics_attrs_old_with_custom = {
+    "http.server.active_requests": _server_active_requests_count_attrs_old,
+    "http.server.duration": _server_duration_attrs_old_with_custom,
+}
+_recommended_metrics_attrs_new_with_custom = {
+    "http.server.active_requests": _server_active_requests_count_attrs_new,
+    "http.server.request.duration": _server_duration_attrs_new_with_custom,
+}
+_recommended_metrics_attrs_both_with_custom = {
+    "http.server.active_requests": _server_active_requests_count_attrs_both,
+    "http.server.duration": _server_duration_attrs_old_with_custom,
+    "http.server.request.duration": _server_duration_attrs_new_with_custom,
+}
+
 
 class TestWsgiApplication(WsgiTestBase):
     def setUp(self):
@@ -221,6 +255,8 @@ def setUp(self):
             },
         )
 
+        clear_labeler()
+
         _OpenTelemetrySemanticConventionStability._initialized = False
 
         self.env_patch.start()
@@ -415,6 +451,41 @@ def test_wsgi_metrics(self):
                             )
         self.assertTrue(number_data_point_seen and histogram_data_point_seen)
 
+    def test_wsgi_metrics_custom_attributes(self):
+        app = otel_wsgi.OpenTelemetryMiddleware(
+            error_wsgi_unhandled_custom_attrs
+        )
+        self.assertRaises(ValueError, app, self.environ, self.start_response)
+        self.assertRaises(ValueError, app, self.environ, self.start_response)
+        self.assertRaises(ValueError, app, self.environ, self.start_response)
+        metrics_list = self.memory_metrics_reader.get_metrics_data()
+        number_data_point_seen = False
+        histogram_data_point_seen = False
+
+        self.assertTrue(len(metrics_list.resource_metrics) != 0)
+        for resource_metric in metrics_list.resource_metrics:
+            self.assertTrue(len(resource_metric.scope_metrics) != 0)
+            for scope_metric in resource_metric.scope_metrics:
+                self.assertTrue(len(scope_metric.metrics) != 0)
+                for metric in scope_metric.metrics:
+                    self.assertIn(metric.name, _expected_metric_names_old)
+                    data_points = list(metric.data.data_points)
+                    self.assertEqual(len(data_points), 1)
+                    for point in data_points:
+                        if isinstance(point, HistogramDataPoint):
+                            self.assertEqual(point.count, 3)
+                            histogram_data_point_seen = True
+                        if isinstance(point, NumberDataPoint):
+                            number_data_point_seen = True
+                        for attr in point.attributes:
+                            self.assertIn(
+                                attr,
+                                _recommended_metrics_attrs_old_with_custom[
+                                    metric.name
+                                ],
+                            )
+        self.assertTrue(number_data_point_seen and histogram_data_point_seen)
+
     def test_wsgi_metrics_new_semconv(self):
         # pylint: disable=too-many-nested-blocks
         app = otel_wsgi.OpenTelemetryMiddleware(error_wsgi_unhandled)
@@ -452,6 +523,45 @@ def test_wsgi_metrics_new_semconv(self):
                             )
         self.assertTrue(number_data_point_seen and histogram_data_point_seen)
 
+    def test_wsgi_metrics_new_semconv_custom_attributes(self):
+        # pylint: disable=too-many-nested-blocks
+        app = otel_wsgi.OpenTelemetryMiddleware(error_wsgi_unhandled)
+        self.assertRaises(ValueError, app, self.environ, self.start_response)
+        self.assertRaises(ValueError, app, self.environ, self.start_response)
+        self.assertRaises(ValueError, app, self.environ, self.start_response)
+        metrics_list = self.memory_metrics_reader.get_metrics_data()
+        number_data_point_seen = False
+        histogram_data_point_seen = False
+
+        self.assertTrue(len(metrics_list.resource_metrics) != 0)
+        for resource_metric in metrics_list.resource_metrics:
+            self.assertTrue(len(resource_metric.scope_metrics) != 0)
+            for scope_metric in resource_metric.scope_metrics:
+                self.assertTrue(len(scope_metric.metrics) != 0)
+                for metric in scope_metric.metrics:
+                    self.assertIn(metric.name, _expected_metric_names_new)
+                    data_points = list(metric.data.data_points)
+                    self.assertEqual(len(data_points), 1)
+                    for point in data_points:
+                        if isinstance(point, HistogramDataPoint):
+                            self.assertEqual(point.count, 3)
+                            if metric.name == "http.server.request.duration":
+                                self.assertEqual(
+                                    point.explicit_bounds,
+                                    HTTP_DURATION_HISTOGRAM_BUCKETS_NEW,
+                                )
+                            histogram_data_point_seen = True
+                        if isinstance(point, NumberDataPoint):
+                            number_data_point_seen = True
+                        for attr in point.attributes:
+                            self.assertIn(
+                                attr,
+                                _recommended_metrics_attrs_new_with_custom[
+                                    metric.name
+                                ],
+                            )
+        self.assertTrue(number_data_point_seen and histogram_data_point_seen)
+
     def test_wsgi_metrics_both_semconv(self):
         # pylint: disable=too-many-nested-blocks
         app = otel_wsgi.OpenTelemetryMiddleware(error_wsgi_unhandled)
@@ -496,6 +606,52 @@ def test_wsgi_metrics_both_semconv(self):
                             )
         self.assertTrue(number_data_point_seen and histogram_data_point_seen)
 
+    def test_wsgi_metrics_both_semconv_custom_attributes(self):
+        # pylint: disable=too-many-nested-blocks
+        app = otel_wsgi.OpenTelemetryMiddleware(error_wsgi_unhandled)
+        self.assertRaises(ValueError, app, self.environ, self.start_response)
+        metrics_list = self.memory_metrics_reader.get_metrics_data()
+        number_data_point_seen = False
+        histogram_data_point_seen = False
+
+        self.assertTrue(len(metrics_list.resource_metrics) != 0)
+        for resource_metric in metrics_list.resource_metrics:
+            self.assertTrue(len(resource_metric.scope_metrics) != 0)
+            for scope_metric in resource_metric.scope_metrics:
+                self.assertTrue(len(scope_metric.metrics) != 0)
+                for metric in scope_metric.metrics:
+                    if metric.unit == "ms":
+                        self.assertEqual(metric.name, "http.server.duration")
+                    elif metric.unit == "s":
+                        self.assertEqual(
+                            metric.name, "http.server.request.duration"
+                        )
+                    else:
+                        self.assertEqual(
+                            metric.name, "http.server.active_requests"
+                        )
+                    data_points = list(metric.data.data_points)
+                    self.assertEqual(len(data_points), 1)
+                    for point in data_points:
+                        if isinstance(point, HistogramDataPoint):
+                            self.assertEqual(point.count, 1)
+                            if metric.name == "http.server.request.duration":
+                                self.assertEqual(
+                                    point.explicit_bounds,
+                                    HTTP_DURATION_HISTOGRAM_BUCKETS_NEW,
+                                )
+                            histogram_data_point_seen = True
+                        if isinstance(point, NumberDataPoint):
+                            number_data_point_seen = True
+                        for attr in point.attributes:
+                            self.assertIn(
+                                attr,
+                                _recommended_metrics_attrs_both_with_custom[
+                                    metric.name
+                                ],
+                            )
+        self.assertTrue(number_data_point_seen and histogram_data_point_seen)
+
     def test_nonstandard_http_method(self):
         self.environ["REQUEST_METHOD"] = "NONSTANDARD"
         app = otel_wsgi.OpenTelemetryMiddleware(simple_wsgi)