Adding new optional post_injection_hook to RequestsInstrumentor

CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+- `opentelemetry-instrumentation-requests` Added support for post-injection-hook.
+  ([#3657](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3657))
+
 ## Version 1.36.0/0.57b0 (2025-07-29)
 
 ### Fixed

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

@@ -86,6 +86,31 @@ def response_hook(span, request_obj, response):
 
 will exclude requests such as ``https://site/client/123/info`` and ``https://site/xyz/healthcheck``.
 
+Post Injection Hook
+*******************
+To customize headers after the current context is injected, you can provide a function that will be called with
+both the headers and request object.
+
+For example, to avoid propagating `tracestate`/`baggage` to non-allowed hosts while still creating a span:
+
+.. code:: python
+
+    allowed_hosts = frozenset(["my-company.com", "my-cloud-provider.com"])
+
+    def post_injection_hook(headers, request):
+        # Parse the domain from the request URL
+        parsed_url = urlparse(request.url)
+        request_host = parsed_url.hostname
+
+        # Remove headers if the host is NOT in the allowed list
+        if request_host not in allowed_hosts:
+            headers.pop("tracestate", None)
+            headers.pop("baggage", None)
+
+    RequestsInstrumentor().instrument(
+        post_injection_hook=post_injection_hook
+    )
+
 API
 ---
 """
@@ -156,6 +181,9 @@ def response_hook(span, request_obj, response):
 
 _RequestHookT = Optional[Callable[[Span, PreparedRequest], None]]
 _ResponseHookT = Optional[Callable[[Span, PreparedRequest, Response], None]]
+_PostInjectionHookT = Optional[
+    Callable[[CaseInsensitiveDict[str], PreparedRequest], None]
+]
 
 
 def _set_http_status_code_attribute(
@@ -194,6 +222,7 @@ def _instrument(
     response_hook: _ResponseHookT = None,
     excluded_urls: ExcludeList | None = None,
     sem_conv_opt_in_mode: _StabilityMode = _StabilityMode.DEFAULT,
+    post_injection_hook: _PostInjectionHookT = None,
 ):
     """Enables tracing of all requests calls that go through
     :code:`requests.session.Session.request` (this includes
@@ -300,6 +329,9 @@ def get_or_create_headers():
             headers = get_or_create_headers()
             inject(headers)
 
+            if callable(post_injection_hook):
+                post_injection_hook(headers, request)
+
             with suppress_http_instrumentation():
                 start_time = default_timer()
                 try:
@@ -450,6 +482,7 @@ def _instrument(self, **kwargs: Any):
         duration_histogram_boundaries = kwargs.get(
             "duration_histogram_boundaries"
         )
+        post_injection_hook = kwargs.get("post_injection_hook")
         meter = get_meter(
             __name__,
             __version__,
@@ -486,6 +519,7 @@ def _instrument(self, **kwargs: Any):
                 else parse_excluded_urls(excluded_urls)
             ),
             sem_conv_opt_in_mode=semconv_opt_in_mode,
+            post_injection_hook=post_injection_hook,
         )
 
     def _uninstrument(self, **kwargs: Any):

instrumentation/opentelemetry-instrumentation-requests/tests/test_requests_integration.py

@@ -322,6 +322,21 @@ def response_hook(span, request_obj, response):
         self.assertEqual(span.name, "name set from hook")
         self.assertEqual(span.attributes["response_hook_attr"], "value")
 
+    def test_post_injection_hook(self):
+        def post_injection_hook(headers, request):
+            headers.pop("traceparent", None)
+
+        RequestsInstrumentor().uninstrument()
+        RequestsInstrumentor().instrument(
+            post_injection_hook=post_injection_hook
+        )
+
+        self.perform_request(self.URL)
+
+        span = self.assert_span()
+        self.assertEqual(span.name, "GET")
+        self.assertNotIn("traceparent", httpretty.last_request().headers)
+
     def test_excluded_urls_explicit(self):
         url_404 = "http://mock/status/404"
         httpretty.register_uri(