chore(baggage): add baggage tags to all spans

ddtrace/internal/utils/__init__.py

@@ -5,6 +5,8 @@
 from typing import Tuple  # noqa:F401
 from typing import Union  # noqa:F401
 
+from ddtrace.internal.constants import BAGGAGE_TAG_PREFIX
+
 
 class ArgumentError(Exception):
     """
@@ -77,7 +79,7 @@ def _get_metas_to_propagate(context):
     metas_to_propagate = []
     # copying context._meta.items() to avoid RuntimeError: dictionary changed size during iteration
     for k, v in list(context._meta.items()):
-        if isinstance(k, str) and k.startswith("_dd.p."):
+        if isinstance(k, str) and (k.startswith("_dd.p.") or k.startswith(BAGGAGE_TAG_PREFIX)):
             metas_to_propagate.append((k, v))
     return metas_to_propagate
 

tests/contrib/fastapi/test_fastapi.py

@@ -944,6 +944,25 @@ def test_baggage_span_tagging_default(client, tracer, test_spans):
     assert request_span.get_tag("baggage.region") is None
 
 
+def test_baggage_span_tags_propagate_to_child_spans(client, tracer, test_spans):
+    # Baggage header contains keys where user.id/account.id are in the default allowlist,
+    # and region is not. We expect the allowed baggage tags to appear on all spans.
+    response = client.get("/", headers={"baggage": "user.id=123,account.id=456,region=us-west"})
+
+    assert response.status_code == 200
+
+    traces = test_spans.pop_traces()
+    assert len(traces) >= 1
+    spans = traces[0]
+    assert len(spans) >= 1
+
+    for span in spans:
+        assert span.get_tag("baggage.user.id") == "123"
+        assert span.get_tag("baggage.account.id") == "456"
+        # Since "region" is not in the default list, its baggage tag should not be present.
+        assert span.get_tag("baggage.region") is None
+
+
 def test_baggage_span_tagging_no_headers(client, tracer, test_spans):
     response = client.get("/", headers={})
     assert response.status_code == 200