Repository: open-telemetry/opentelemetry-python-contrib

Issue:
FastAPI: Capture request/response headers as span attributes
part of #906


Discussion:
Hi @owais Can you assign this to me?
Hi @owais I guess by mistake you have assigned this to @ashu658 instead of me.
Can you please assign it to me?

Resolving patch:
diff --git a/instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py b/instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py
--- a/instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py
+++ b/instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py
@@ -91,6 +91,57 @@ def client_response_hook(span: Span, message: dict):
 
    OpenTelemetryMiddleware().(application, server_request_hook=server_request_hook, client_request_hook=client_request_hook, client_response_hook=client_response_hook)
 
+Capture HTTP request and response headers
+*****************************************
+You can configure the agent to capture predefined HTTP headers as span attributes, according to the `semantic convention <https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-request-and-response-headers>`_.
+
+Request headers
+***************
+To capture predefined HTTP request headers as span attributes, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST``
+to a comma-separated list of HTTP header names.
+
+For example,
+
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="content-type,custom_request_header"
+
+will extract ``content-type`` and ``custom_request_header`` from request headers and add them as span attributes.
+
+It is recommended that you should give the correct names of the headers to be captured in the environment variable.
+Request header names in ASGI are case insensitive. So, giving header name as ``CUStom-Header`` in environment variable will be able capture header with name ``custom-header``.
+
+The name of the added span attribute will follow the format ``http.request.header.<header_name>`` where ``<header_name>`` being the normalized HTTP header name (lowercase, with - characters replaced by _ ).
+The value of the attribute will be single item list containing all the header values.
+
+Example of the added span attribute,
+``http.request.header.custom_request_header = ["<value1>,<value2>"]``
+
+Response headers
+****************
+To capture predefined HTTP response headers as span attributes, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE``
+to a comma-separated list of HTTP header names.
+
+For example,
+
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="content-type,custom_response_header"
+
+will extract ``content-type`` and ``custom_response_header`` from response headers and add them as span attributes.
+
+It is recommended that you should give the correct names of the headers to be captured in the environment variable.
+Response header names captured in ASGI are case insensitive. So, giving header name as ``CUStomHeader`` in environment variable will be able capture header with name ``customheader``.
+
+The name of the added span attribute will follow the format ``http.response.header.<header_name>`` where ``<header_name>`` being the normalized HTTP header name (lowercase, with - characters replaced by _ ).
+The value of the attribute will be single item list containing all the header values.
+
+Example of the added span attribute,
+``http.response.header.custom_response_header = ["<value1>,<value2>"]``
+
+Note:
+    Environment variable names to caputre http headers are still experimental, and thus are subject to change.
+
 API
 ---
 """
diff --git a/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py b/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
--- a/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
+++ b/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
@@ -74,6 +74,58 @@ def client_response_hook(span: Span, message: dict):
 
    FastAPIInstrumentor().instrument(server_request_hook=server_request_hook, client_request_hook=client_request_hook, client_response_hook=client_response_hook)
 
+
+Capture HTTP request and response headers
+*****************************************
+You can configure the agent to capture predefined HTTP headers as span attributes, according to the `semantic convention <https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-request-and-response-headers>`_.
+
+Request headers
+***************
+To capture predefined HTTP request headers as span attributes, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST``
+to a comma-separated list of HTTP header names.
+
+For example,
+
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="content-type,custom_request_header"
+
+will extract ``content-type`` and ``custom_request_header`` from request headers and add them as span attributes.
+
+It is recommended that you should give the correct names of the headers to be captured in the environment variable.
+Request header names in FastAPI are case insensitive. So, giving header name as ``CUStom-Header`` in environment variable will be able capture header with name ``custom-header``.
+
+The name of the added span attribute will follow the format ``http.request.header.<header_name>`` where ``<header_name>`` being the normalized HTTP header name (lowercase, with - characters replaced by _ ).
+The value of the attribute will be single item list containing all the header values.
+
+Example of the added span attribute,
+``http.request.header.custom_request_header = ["<value1>,<value2>"]``
+
+Response headers
+****************
+To capture predefined HTTP response headers as span attributes, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE``
+to a comma-separated list of HTTP header names.
+
+For example,
+
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="content-type,custom_response_header"
+
+will extract ``content-type`` and ``custom_response_header`` from response headers and add them as span attributes.
+
+It is recommended that you should give the correct names of the headers to be captured in the environment variable.
+Response header names captured in FastAPI are case insensitive. So, giving header name as ``CUStomHeader`` in environment variable will be able capture header with name ``customheader``.
+
+The name of the added span attribute will follow the format ``http.response.header.<header_name>`` where ``<header_name>`` being the normalized HTTP header name (lowercase, with - characters replaced by _ ).
+The value of the attribute will be single item list containing all the header values.
+
+Example of the added span attribute,
+``http.response.header.custom_response_header = ["<value1>,<value2>"]``
+
+Note:
+    Environment variable names to caputre http headers are still experimental, and thus are subject to change.
+
 API
 ---
 """


Test patch:
diff --git a/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py b/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
--- a/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
+++ b/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
@@ -16,6 +16,7 @@
 from unittest.mock import patch
 
 import fastapi
+from fastapi.responses import JSONResponse
 from fastapi.testclient import TestClient
 
 import opentelemetry.instrumentation.fastapi as otel_fastapi
@@ -23,8 +24,13 @@
 from opentelemetry.instrumentation.asgi import OpenTelemetryMiddleware
 from opentelemetry.sdk.resources import Resource
 from opentelemetry.semconv.trace import SpanAttributes
+from opentelemetry.test.globals_test import reset_trace_globals
 from opentelemetry.test.test_base import TestBase
-from opentelemetry.util.http import get_excluded_urls
+from opentelemetry.util.http import (
+    OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST,
+    OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE,
+    get_excluded_urls,
+)
 
 
 class TestFastAPIManualInstrumentation(TestBase):
@@ -375,3 +381,314 @@ def test_mark_span_internal_in_presence_of_span_from_other_framework(self):
         self.assertEqual(
             parent_span.context.span_id, span_list[3].context.span_id
         )
+
+
+class TestHTTPAppWithCustomHeaders(TestBase):
+    def setUp(self):
+        super().setUp()
+        self.env_patch = patch.dict(
+            "os.environ",
+            {
+                OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST: "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3",
+                OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE: "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3",
+            },
+        )
+        self.env_patch.start()
+        self.app = self._create_app()
+        otel_fastapi.FastAPIInstrumentor().instrument_app(self.app)
+        self.client = TestClient(self.app)
+
+    def tearDown(self) -> None:
+        super().tearDown()
+        self.env_patch.stop()
+        with self.disable_logging():
+            otel_fastapi.FastAPIInstrumentor().uninstrument_app(self.app)
+
+    @staticmethod
+    def _create_app():
+        app = fastapi.FastAPI()
+
+        @app.get("/foobar")
+        async def _():
+            headers = {
+                "custom-test-header-1": "test-header-value-1",
+                "custom-test-header-2": "test-header-value-2",
+            }
+            content = {"message": "hello world"}
+            return JSONResponse(content=content, headers=headers)
+
+        return app
+
+    def test_http_custom_request_headers_in_span_attributes(self):
+        expected = {
+            "http.request.header.custom_test_header_1": (
+                "test-header-value-1",
+            ),
+            "http.request.header.custom_test_header_2": (
+                "test-header-value-2",
+            ),
+        }
+        resp = self.client.get(
+            "/foobar",
+            headers={
+                "custom-test-header-1": "test-header-value-1",
+                "custom-test-header-2": "test-header-value-2",
+            },
+        )
+        self.assertEqual(200, resp.status_code)
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 3)
+
+        server_span = [
+            span for span in span_list if span.kind == trace.SpanKind.SERVER
+        ][0]
+
+        self.assertSpanHasAttributes(server_span, expected)
+
+    def test_http_custom_request_headers_not_in_span_attributes(self):
+        not_expected = {
+            "http.request.header.custom_test_header_3": (
+                "test-header-value-3",
+            ),
+        }
+        resp = self.client.get(
+            "/foobar",
+            headers={
+                "custom-test-header-1": "test-header-value-1",
+                "custom-test-header-2": "test-header-value-2",
+            },
+        )
+        self.assertEqual(200, resp.status_code)
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 3)
+
+        server_span = [
+            span for span in span_list if span.kind == trace.SpanKind.SERVER
+        ][0]
+
+        for key, _ in not_expected.items():
+            self.assertNotIn(key, server_span.attributes)
+
+    def test_http_custom_response_headers_in_span_attributes(self):
+        expected = {
+            "http.response.header.custom_test_header_1": (
+                "test-header-value-1",
+            ),
+            "http.response.header.custom_test_header_2": (
+                "test-header-value-2",
+            ),
+        }
+        resp = self.client.get("/foobar")
+        self.assertEqual(200, resp.status_code)
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 3)
+
+        server_span = [
+            span for span in span_list if span.kind == trace.SpanKind.SERVER
+        ][0]
+        self.assertSpanHasAttributes(server_span, expected)
+
+    def test_http_custom_response_headers_not_in_span_attributes(self):
+        not_expected = {
+            "http.reponse.header.custom_test_header_3": (
+                "test-header-value-3",
+            ),
+        }
+        resp = self.client.get("/foobar")
+        self.assertEqual(200, resp.status_code)
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 3)
+
+        server_span = [
+            span for span in span_list if span.kind == trace.SpanKind.SERVER
+        ][0]
+
+        for key, _ in not_expected.items():
+            self.assertNotIn(key, server_span.attributes)
+
+
+class TestWebSocketAppWithCustomHeaders(TestBase):
+    def setUp(self):
+        super().setUp()
+        self.env_patch = patch.dict(
+            "os.environ",
+            {
+                OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST: "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3",
+                OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE: "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3",
+            },
+        )
+        self.env_patch.start()
+        self.app = self._create_app()
+        otel_fastapi.FastAPIInstrumentor().instrument_app(self.app)
+        self.client = TestClient(self.app)
+
+    def tearDown(self) -> None:
+        super().tearDown()
+        self.env_patch.stop()
+        with self.disable_logging():
+            otel_fastapi.FastAPIInstrumentor().uninstrument_app(self.app)
+
+    @staticmethod
+    def _create_app():
+        app = fastapi.FastAPI()
+
+        @app.websocket("/foobar_web")
+        async def _(websocket: fastapi.WebSocket):
+            message = await websocket.receive()
+            if message.get("type") == "websocket.connect":
+                await websocket.send(
+                    {
+                        "type": "websocket.accept",
+                        "headers": [
+                            (b"custom-test-header-1", b"test-header-value-1"),
+                            (b"custom-test-header-2", b"test-header-value-2"),
+                        ],
+                    }
+                )
+                await websocket.send_json({"message": "hello world"})
+                await websocket.close()
+            if message.get("type") == "websocket.disconnect":
+                pass
+
+        return app
+
+    def test_web_socket_custom_request_headers_in_span_attributes(self):
+        expected = {
+            "http.request.header.custom_test_header_1": (
+                "test-header-value-1",
+            ),
+            "http.request.header.custom_test_header_2": (
+                "test-header-value-2",
+            ),
+        }
+
+        with self.client.websocket_connect(
+            "/foobar_web",
+            headers={
+                "custom-test-header-1": "test-header-value-1",
+                "custom-test-header-2": "test-header-value-2",
+            },
+        ) as websocket:
+            data = websocket.receive_json()
+            self.assertEqual(data, {"message": "hello world"})
+
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 5)
+
+        server_span = [
+            span for span in span_list if span.kind == trace.SpanKind.SERVER
+        ][0]
+
+        self.assertSpanHasAttributes(server_span, expected)
+
+    def test_web_socket_custom_request_headers_not_in_span_attributes(self):
+        not_expected = {
+            "http.request.header.custom_test_header_3": (
+                "test-header-value-3",
+            ),
+        }
+
+        with self.client.websocket_connect(
+            "/foobar_web",
+            headers={
+                "custom-test-header-1": "test-header-value-1",
+                "custom-test-header-2": "test-header-value-2",
+            },
+        ) as websocket:
+            data = websocket.receive_json()
+            self.assertEqual(data, {"message": "hello world"})
+
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 5)
+
+        server_span = [
+            span for span in span_list if span.kind == trace.SpanKind.SERVER
+        ][0]
+
+        for key, _ in not_expected.items():
+            self.assertNotIn(key, server_span.attributes)
+
+    def test_web_socket_custom_response_headers_in_span_attributes(self):
+        expected = {
+            "http.response.header.custom_test_header_1": (
+                "test-header-value-1",
+            ),
+            "http.response.header.custom_test_header_2": (
+                "test-header-value-2",
+            ),
+        }
+
+        with self.client.websocket_connect("/foobar_web") as websocket:
+            data = websocket.receive_json()
+            self.assertEqual(data, {"message": "hello world"})
+
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 5)
+
+        server_span = [
+            span for span in span_list if span.kind == trace.SpanKind.SERVER
+        ][0]
+
+        self.assertSpanHasAttributes(server_span, expected)
+
+    def test_web_socket_custom_response_headers_not_in_span_attributes(self):
+        not_expected = {
+            "http.reponse.header.custom_test_header_3": (
+                "test-header-value-3",
+            ),
+        }
+
+        with self.client.websocket_connect("/foobar_web") as websocket:
+            data = websocket.receive_json()
+            self.assertEqual(data, {"message": "hello world"})
+
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 5)
+
+        server_span = [
+            span for span in span_list if span.kind == trace.SpanKind.SERVER
+        ][0]
+
+        for key, _ in not_expected.items():
+            self.assertNotIn(key, server_span.attributes)
+
+
+class TestNonRecordingSpanWithCustomHeaders(TestBase):
+    def setUp(self):
+        super().setUp()
+        self.env_patch = patch.dict(
+            "os.environ",
+            {
+                OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST: "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3",
+            },
+        )
+        self.env_patch.start()
+        self.app = fastapi.FastAPI()
+
+        @self.app.get("/foobar")
+        async def _():
+            return {"message": "hello world"}
+
+        reset_trace_globals()
+        tracer_provider = trace.NoOpTracerProvider()
+        trace.set_tracer_provider(tracer_provider=tracer_provider)
+
+        self._instrumentor = otel_fastapi.FastAPIInstrumentor()
+        self._instrumentor.instrument_app(self.app)
+        self.client = TestClient(self.app)
+
+    def tearDown(self) -> None:
+        super().tearDown()
+        with self.disable_logging():
+            self._instrumentor.uninstrument_app(self.app)
+
+    def test_custom_header_not_present_in_non_recording_span(self):
+        resp = self.client.get(
+            "/foobar",
+            headers={
+                "custom-test-header-1": "test-header-value-1",
+            },
+        )
+        self.assertEqual(200, resp.status_code)
+        span_list = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 0)