Add fallback decoding for asgi headers

CHANGELOG.md

@@ -19,6 +19,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#2537](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2537))
 - `opentelemetry-instrumentation-asgi`, `opentelemetry-instrumentation-fastapi` Add ability to disable internal HTTP send and receive spans
   ([#2802](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2802))
+- `opentelemetry-instrumentation-asgi`, Add fallback decoding for ASGI headers
+  ([#2837](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2837))
 
 ### Breaking changes
 

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

@@ -284,17 +284,17 @@ def get(
         # ASGI header keys are in lower case
         key = key.lower()
         decoded = [
-            _value.decode("utf8")
+            _decode_header_item(_value)
             for (_key, _value) in headers
-            if _key.decode("utf8").lower() == key
+            if _decode_header_item(_key).lower() == key
         ]
         if not decoded:
             return None
         return decoded
 
     def keys(self, carrier: dict) -> typing.List[str]:
         headers = carrier.get("headers") or []
-        return [_key.decode("utf8") for (_key, _value) in headers]
+        return [_decode_header_item(_key) for (_key, _value) in headers]
 
 
 asgi_getter = ASGIGetter()
@@ -410,7 +410,9 @@ def collect_custom_headers_attributes(
     if raw_headers:
         for key, value in raw_headers:
             # Decode headers before processing.
-            headers[key.decode()].append(value.decode())
+            headers[_decode_header_item(key)].append(
+                _decode_header_item(value)
+            )
 
     return sanitize.sanitize_header_values(
         headers,
@@ -979,3 +981,13 @@ def _parse_active_request_count_attrs(
         _server_active_requests_count_attrs_new,
         sem_conv_opt_in_mode,
     )
+
+
+def _decode_header_item(value):
+    try:
+        return value.decode("utf-8")
+    except ValueError:
+        # ASGI header encoding specs, see:
+        # - https://asgi.readthedocs.io/en/latest/specs/www.html#wsgi-encoding-differences (see: WSGI encoding differences)
+        # - https://docs.python.org/3/library/codecs.html#text-encodings (see: Text Encodings)
+        return value.decode("unicode_escape")

instrumentation/opentelemetry-instrumentation-asgi/tests/test_asgi_custom_headers.py

@@ -130,6 +130,10 @@ async def test_http_custom_request_headers_in_span_attributes(self):
                 (b"Regex-Test-Header-1", b"Regex Test Value 1"),
                 (b"regex-test-header-2", b"RegexTestValue2,RegexTestValue3"),
                 (b"My-Secret-Header", b"My Secret Value"),
+                (
+                    b"non-utf8-header",
+                    b"Moto Z\xb2",
+                ),
             ]
         )
         self.seed_app(self.app)
@@ -147,6 +151,7 @@ async def test_http_custom_request_headers_in_span_attributes(self):
             "http.request.header.regex_test_header_2": (
                 "RegexTestValue2,RegexTestValue3",
             ),
+            "http.request.header.non_utf8_header": ("Moto Z²",),
             "http.request.header.my_secret_header": ("[REDACTED]",),
         }
         for span in span_list:
@@ -418,7 +423,7 @@ async def test_websocket_custom_response_headers_not_in_span_attributes(
 
 
 SANITIZE_FIELDS_TEST_VALUE = ".*my-secret.*"
-SERVER_REQUEST_TEST_VALUE = "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3,Regex-Test-Header-.*,Regex-Invalid-Test-Header-.*,.*my-secret.*"
+SERVER_REQUEST_TEST_VALUE = "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3,Regex-Test-Header-.*,Regex-Invalid-Test-Header-.*,.*my-secret.*,non-utf8-header"
 SERVER_RESPONSE_TEST_VALUE = "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3,my-custom-regex-header-.*,invalid-regex-header-.*,.*my-secret.*"