Repository: open-telemetry/opentelemetry-python-contrib

Issue:
Add more features for adding HTTP request / response headers to spans.
I already have https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1172 open for this, and I'll be breaking it in to smaller pieces at @lzchen 's request.

**Is your feature request related to a problem?**
Currently, you can only provide a list of full HTTP request / response header names to be added to the span.

There is also no capacity for header value redaction.

**Describe the solution you'd like**
It would be nice to be able to specify a regex or "all" to get all headers.

Header value redaction is also a must-have for us.

**Describe alternatives you've considered**
I considered doing this in my application, but it makes more sense to add it here.



Discussion:

Resolving patch:
diff --git a/instrumentation/opentelemetry-instrumentation-flask/src/opentelemetry/instrumentation/flask/__init__.py b/instrumentation/opentelemetry-instrumentation-flask/src/opentelemetry/instrumentation/flask/__init__.py
--- a/instrumentation/opentelemetry-instrumentation-flask/src/opentelemetry/instrumentation/flask/__init__.py
+++ b/instrumentation/opentelemetry-instrumentation-flask/src/opentelemetry/instrumentation/flask/__init__.py
@@ -95,8 +95,9 @@ def hello():
 
 Exclude lists
 *************
-To exclude certain URLs from being tracked, set the environment variable ``OTEL_PYTHON_FLASK_EXCLUDED_URLS``
-(or ``OTEL_PYTHON_EXCLUDED_URLS`` as fallback) with comma delimited regexes representing which URLs to exclude.
+To exclude certain URLs from tracking, set the environment variable ``OTEL_PYTHON_FLASK_EXCLUDED_URLS``
+(or ``OTEL_PYTHON_EXCLUDED_URLS`` to cover all instrumentations) to a string of comma delimited regexes that match the
+URLs.
 
 For example,
 
@@ -106,7 +107,7 @@ def hello():
 
 will exclude requests such as ``https://site/client/123/info`` and ``https://site/xyz/healthcheck``.
 
-You can also pass the comma delimited regexes to the ``instrument_app`` method directly:
+You can also pass comma delimited regexes directly to the ``instrument_app`` method:
 
 .. code-block:: python
 
@@ -115,8 +116,15 @@ def hello():
 Request/Response hooks
 **********************
 
-Utilize request/response hooks to execute custom logic to be performed before/after performing a request. Environ is an instance of WSGIEnvironment (flask.request.environ).
-Response_headers is a list of key-value (tuples) representing the response headers returned from the response.
+This instrumentation supports request and response hooks. These are functions that get called
+right after a span is created for a request and right before the span is finished for the response.
+
+- The client request hook is called with the internal span and an instance of WSGIEnvironment (flask.request.environ)
+  when the method ``receive`` is called.
+- The client response hook is called with the internal span, the status of the response and a list of key-value (tuples)
+  representing the response headers returned from the response when the method ``send`` is called.
+
+For example,
 
 .. code-block:: python
 
@@ -130,58 +138,97 @@ def response_hook(span: Span, status: str, response_headers: List):
 
     FlaskInstrumentation().instrument(request_hook=request_hook, response_hook=response_hook)
 
-Flask Request object reference: https://flask.palletsprojects.com/en/2.0.x/api/#flask.Request
+Flask Request object reference: https://flask.palletsprojects.com/en/2.1.x/api/#flask.Request
 
 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>`_.
+You can configure the agent to capture specified 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.
+To capture HTTP request headers as span attributes, set the environment variable
+``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST`` to a comma delimited 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.
+will extract ``content-type`` and ``custom_request_header`` from the request headers and add them as span attributes.
+
+Request header names in Flask are case-insensitive and ``-`` characters are replaced by ``_``. So, giving the header
+name as ``CUStom_Header`` in the environment variable will capture the header named ``custom-header``.
+
+Regular expressions may also be used to match multiple headers that correspond to the given pattern.  For example:
+::
 
-It is recommended that you should give the correct names of the headers to be captured in the environment variable.
-Request header names in flask are case insensitive and - characters are replaced by _. So, giving header name as ``CUStom_Header`` in environment variable will be able capture header with name ``custom-header``.
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="Accept.*,X-.*"
 
-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.
+Would match all request headers that start with ``Accept`` and ``X-``.
 
-Example of the added span attribute,
+To capture all request headers, set ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST`` to ``".*"``.
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST=".*"
+
+The name of the added span attribute will follow the format ``http.request.header.<header_name>`` where ``<header_name>``
+is the normalized HTTP header name (lowercase, with ``-`` replaced by ``_``). The value of the attribute will be a
+single item list containing all the header values.
+
+For example:
 ``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.
+To capture HTTP response headers as span attributes, set the environment variable
+``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE`` to a comma delimited 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.
+will extract ``content-type`` and ``custom_response_header`` from the 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 flask are case insensitive. So, giving header name as ``CUStomHeader`` in environment variable will be able capture header with name ``customheader``.
+Response header names in Flask are case-insensitive. So, giving the header name as ``CUStom-Header`` in the environment
+variable will capture the header named ``custom-header``.
 
-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.
+Regular expressions may also be used to match multiple headers that correspond to the given pattern.  For example:
+::
 
-Example of the added span attribute,
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="Content.*,X-.*"
+
+Would match all response headers that start with ``Content`` and ``X-``.
+
+To capture all response headers, set ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE`` to ``".*"``.
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE=".*"
+
+The name of the added span attribute will follow the format ``http.response.header.<header_name>`` where ``<header_name>``
+is the normalized HTTP header name (lowercase, with ``-`` replaced by ``_``). The value of the attribute will be a
+single item list containing all the header values.
+
+For example:
 ``http.response.header.custom_response_header = ["<value1>,<value2>"]``
 
+Sanitizing headers
+******************
+In order to prevent storing sensitive data such as personally identifiable information (PII), session keys, passwords,
+etc, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS``
+to a comma delimited list of HTTP header names to be sanitized.  Regexes may be used, and all header names will be
+matched in a case-insensitive manner.
+
+For example,
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS=".*session.*,set-cookie"
+
+will replace the value of headers such as ``session-id`` and ``set-cookie`` with ``[REDACTED]`` in the span.
+
 Note:
-    Environment variable names to capture http headers are still experimental, and thus are subject to change.
+    The environment variable names used to capture HTTP headers are still experimental, and thus are subject to change.
 
 API
 ---


Test patch:
diff --git a/instrumentation/opentelemetry-instrumentation-flask/tests/base_test.py b/instrumentation/opentelemetry-instrumentation-flask/tests/base_test.py
--- a/instrumentation/opentelemetry-instrumentation-flask/tests/base_test.py
+++ b/instrumentation/opentelemetry-instrumentation-flask/tests/base_test.py
@@ -42,6 +42,13 @@ def _custom_response_headers():
         resp.headers[
             "my-custom-header"
         ] = "my-custom-value-1,my-custom-header-2"
+        resp.headers[
+            "my-custom-regex-header-1"
+        ] = "my-custom-regex-value-1,my-custom-regex-value-2"
+        resp.headers[
+            "My-Custom-Regex-Header-2"
+        ] = "my-custom-regex-value-3,my-custom-regex-value-4"
+        resp.headers["my-secret-header"] = "my-secret-value"
         return resp
 
     def _common_initialization(self):
diff --git a/instrumentation/opentelemetry-instrumentation-flask/tests/test_programmatic.py b/instrumentation/opentelemetry-instrumentation-flask/tests/test_programmatic.py
--- a/instrumentation/opentelemetry-instrumentation-flask/tests/test_programmatic.py
+++ b/instrumentation/opentelemetry-instrumentation-flask/tests/test_programmatic.py
@@ -36,7 +36,12 @@
 from opentelemetry.sdk.resources import Resource
 from opentelemetry.semconv.trace import SpanAttributes
 from opentelemetry.test.wsgitestutil import WsgiTestBase
-from opentelemetry.util.http import get_excluded_urls
+from opentelemetry.util.http import (
+    OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS,
+    OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST,
+    OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE,
+    get_excluded_urls,
+)
 
 # pylint: disable=import-error
 from .base_test import InstrumentationTest
@@ -558,18 +563,18 @@ def test_mark_span_internal_in_presence_of_span_from_other_framework(self):
         )
 
 
+@patch.dict(
+    "os.environ",
+    {
+        OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS: ".*my-secret.*",
+        OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST: "Custom-Test-Header-1,Custom-Test-Header-2,Custom-Test-Header-3,Regex-Test-Header-.*,Regex-Invalid-Test-Header-.*,.*my-secret.*",
+        OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE: "content-type,content-length,my-custom-header,invalid-header,my-custom-regex-header-.*,invalid-regex-header-.*,.*my-secret.*",
+    },
+)
 class TestCustomRequestResponseHeaders(InstrumentationTest, WsgiTestBase):
     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": "content-type,content-length,my-custom-header,invalid-header",
-            },
-        )
-        self.env_patch.start()
         self.app = Flask(__name__)
         FlaskInstrumentor().instrument_app(self.app)
 
@@ -577,7 +582,6 @@ def setUp(self):
 
     def tearDown(self):
         super().tearDown()
-        self.env_patch.stop()
         with self.disable_logging():
             FlaskInstrumentor().uninstrument_app(self.app)
 
@@ -585,6 +589,9 @@ def test_custom_request_header_added_in_server_span(self):
         headers = {
             "Custom-Test-Header-1": "Test Value 1",
             "Custom-Test-Header-2": "TestValue2,TestValue3",
+            "Regex-Test-Header-1": "Regex Test Value 1",
+            "regex-test-header-2": "RegexTestValue2,RegexTestValue3",
+            "My-Secret-Header": "My Secret Value",
         }
         resp = self.client.get("/hello/123", headers=headers)
         self.assertEqual(200, resp.status_code)
@@ -594,6 +601,11 @@ def test_custom_request_header_added_in_server_span(self):
             "http.request.header.custom_test_header_2": (
                 "TestValue2,TestValue3",
             ),
+            "http.request.header.regex_test_header_1": ("Regex Test Value 1",),
+            "http.request.header.regex_test_header_2": (
+                "RegexTestValue2,RegexTestValue3",
+            ),
+            "http.request.header.my_secret_header": ("[REDACTED]",),
         }
         self.assertEqual(span.kind, trace.SpanKind.SERVER)
         self.assertSpanHasAttributes(span, expected)
@@ -604,6 +616,9 @@ def test_custom_request_header_not_added_in_internal_span(self):
             headers = {
                 "Custom-Test-Header-1": "Test Value 1",
                 "Custom-Test-Header-2": "TestValue2,TestValue3",
+                "Regex-Test-Header-1": "Regex Test Value 1",
+                "regex-test-header-2": "RegexTestValue2,RegexTestValue3",
+                "My-Secret-Header": "My Secret Value",
             }
             resp = self.client.get("/hello/123", headers=headers)
             self.assertEqual(200, resp.status_code)
@@ -613,6 +628,13 @@ def test_custom_request_header_not_added_in_internal_span(self):
                 "http.request.header.custom_test_header_2": (
                     "TestValue2,TestValue3",
                 ),
+                "http.request.header.regex_test_header_1": (
+                    "Regex Test Value 1",
+                ),
+                "http.request.header.regex_test_header_2": (
+                    "RegexTestValue2,RegexTestValue3",
+                ),
+                "http.request.header.my_secret_header": ("[REDACTED]",),
             }
             self.assertEqual(span.kind, trace.SpanKind.INTERNAL)
             for key, _ in not_expected.items():
@@ -630,6 +652,13 @@ def test_custom_response_header_added_in_server_span(self):
             "http.response.header.my_custom_header": (
                 "my-custom-value-1,my-custom-header-2",
             ),
+            "http.response.header.my_custom_regex_header_1": (
+                "my-custom-regex-value-1,my-custom-regex-value-2",
+            ),
+            "http.response.header.my_custom_regex_header_2": (
+                "my-custom-regex-value-3,my-custom-regex-value-4",
+            ),
+            "http.response.header.my_secret_header": ("[REDACTED]",),
         }
         self.assertEqual(span.kind, trace.SpanKind.SERVER)
         self.assertSpanHasAttributes(span, expected)
@@ -648,6 +677,13 @@ def test_custom_response_header_not_added_in_internal_span(self):
                 "http.response.header.my_custom_header": (
                     "my-custom-value-1,my-custom-header-2",
                 ),
+                "http.response.header.my_custom_regex_header_1": (
+                    "my-custom-regex-value-1,my-custom-regex-value-2",
+                ),
+                "http.response.header.my_custom_regex_header_2": (
+                    "my-custom-regex-value-3,my-custom-regex-value-4",
+                ),
+                "http.response.header.my_secret_header": ("[REDACTED]",),
             }
             self.assertEqual(span.kind, trace.SpanKind.INTERNAL)
             for key, _ in not_expected.items():