fix fof wsgi, test in falcon

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

@@ -490,6 +490,26 @@ def test_custom_request_header_added_in_server_span(self):
         for key, _ in not_expected.items():
             self.assertNotIn(key, span.attributes)
 
+    def test_repeated_request_header_added_in_server_span(self):
+        headers = [
+            ("Custom-Test-Header-1", "Test Value 1"),
+            ("Custom-Test-Header-1", "Test Value 2"),
+        ]
+        self.client().simulate_request(
+            method="GET", path="/hello", headers=headers
+        )
+        span = self.memory_exporter.get_finished_spans()[0]
+        assert span.status.is_ok
+
+        expected = {
+            "http.request.header.custom_test_header_1": (
+                "Test Value 1,Test Value 2",
+            ),
+        }
+
+        self.assertEqual(span.kind, trace.SpanKind.SERVER)
+        self.assertSpanHasAttributes(span, expected)
+
     def test_custom_request_header_not_added_in_internal_span(self):
         tracer = trace.get_tracer(__name__)
         with tracer.start_as_current_span("test", kind=trace.SpanKind.SERVER):

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

@@ -358,12 +358,15 @@ def collect_custom_request_headers_attributes(environ):
             OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS
         )
     )
+    headers = {}
 
-    headers = {
-        key[_CARRIER_KEY_PREFIX_LEN:].replace("_", "-"): val
-        for key, val in environ.items()
-        if key.startswith(_CARRIER_KEY_PREFIX)
-    }
+    for key, val in environ.items():
+        if key.startswith(_CARRIER_KEY_PREFIX):
+            header_key = key[_CARRIER_KEY_PREFIX_LEN:].replace("_", "-").lower()
+            if header_key in headers:
+                headers[header_key] += "," + val
+            else:
+                headers[header_key] = val
 
     return sanitize.sanitize_header_values(
         headers,
@@ -387,7 +390,12 @@ def collect_custom_response_headers_attributes(response_headers):
     )
     response_headers_dict = {}
     if response_headers:
-        response_headers_dict = dict(response_headers)
+        for key, val in response_headers:
+            key = key.lower()
+            if key in response_headers_dict:
+                response_headers_dict[key] += "," + val
+            else:
+                response_headers_dict[key] = val
 
     return sanitize.sanitize_header_values(
         response_headers_dict,