Added trace response headers to Falcon

Author: owais

.github/workflows/test.yml

@@ -6,7 +6,7 @@ on:
     - 'release/*'
   pull_request:
 env:
-  CORE_REPO_SHA: cad261e5dae1fe986c87e6965664b45cc9ab73c3
+  CORE_REPO_SHA: f6b04c483f6c416e1927f010c07e71a17a5d79d0
 
 jobs:
   build:

CHANGELOG.md

@@ -21,6 +21,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#299](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/299))
 - `opentelemetry-instrumenation-django` now supports request and response hooks.
   ([#407](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/407))
+- `opentelemetry-instrumenation-falcon` added trace response headers support to Falcon.
+  ([#432](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/432))
 
 ### Removed
 - Remove `http.status_text` from span attributes

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

@@ -52,6 +52,10 @@ def on_get(self, req, resp):
 from opentelemetry import context, trace
 from opentelemetry.instrumentation.falcon.version import __version__
 from opentelemetry.instrumentation.instrumentor import BaseInstrumentor
+from opentelemetry.instrumentation.propagators import (
+    FuncSetter,
+    get_global_back_propagator,
+)
 from opentelemetry.instrumentation.utils import (
     extract_attributes_from_object,
     http_status_to_status_code,
@@ -148,6 +152,8 @@ def _start_response(status, response_headers, *args, **kwargs):
 class _TraceMiddleware:
     # pylint:disable=R0201,W0613
 
+    back_propagation_setter = FuncSetter(falcon.api.Response.append_header)
+
     def __init__(self, tracer=None, traced_request_attrs=None):
         self.tracer = tracer
         self._traced_request_attrs = _traced_request_attrs
@@ -209,3 +215,7 @@ def process_response(
                     description=reason,
                 )
             )
+
+        propagator = get_global_back_propagator()
+        if propagator:
+            propagator.inject(resp, setter=self.back_propagation_setter)

instrumentation/opentelemetry-instrumentation-falcon/tests/test_falcon.py

@@ -17,8 +17,13 @@
 from falcon import testing
 
 from opentelemetry.instrumentation.falcon import FalconInstrumentor
+from opentelemetry.instrumentation.propagators import (
+    TraceResponsePropagator,
+    get_global_back_propagator,
+    set_global_back_propagator,
+)
 from opentelemetry.test.test_base import TestBase
-from opentelemetry.trace import StatusCode
+from opentelemetry.trace import StatusCode, format_span_id, format_trace_id
 from opentelemetry.util.http import get_excluded_urls, get_traced_request_attrs
 
 from .app import make_app
@@ -192,6 +197,28 @@ def test_traced_request_attributes(self):
         self.assertEqual(span.attributes["query_string"], "q=abc")
         self.assertNotIn("not_available_attr", span.attributes)
 
+    def test_trace_response(self):
+        orig = get_global_back_propagator()
+        set_global_back_propagator(TraceResponsePropagator())
+
+        response = self.client().simulate_get(path="/hello?q=abc")
+        headers = response.headers
+        span = self.memory_exporter.get_finished_spans()[0]
+
+        self.assertIn("traceresponse", headers)
+        self.assertEqual(
+            headers["access-control-expose-headers"], "traceresponse",
+        )
+        self.assertEqual(
+            headers["traceresponse"],
+            "00-{0}-{1}-01".format(
+                format_trace_id(span.get_span_context().trace_id),
+                format_span_id(span.get_span_context().span_id),
+            ),
+        )
+
+        set_global_back_propagator(orig)
+
     def test_traced_not_recording(self):
         mock_tracer = Mock()
         mock_span = Mock()