fix(httpx): Prevent Sentry baggage duplication (#3728)

Sentry baggage will get added to an HTTPX request multiple times if the same request is repeated. To prevent this from occurring, we can strip any existing Sentry baggage before adding Sentry baggage to the request.

Fixes #3709

---------

Co-authored-by: Ivana Kellyer <ivana.kellyer@sentry.io>
Co-authored-by: Anton Pirker <anton.pirker@sentry.io>

sentry_sdk/integrations/httpx.py

@@ -2,7 +2,7 @@
 from sentry_sdk.consts import OP, SPANDATA
 from sentry_sdk.integrations import Integration, DidNotEnable
 from sentry_sdk.tracing import BAGGAGE_HEADER_NAME
-from sentry_sdk.tracing_utils import should_propagate_trace
+from sentry_sdk.tracing_utils import Baggage, should_propagate_trace
 from sentry_sdk.utils import (
     SENSITIVE_DATA_SUBSTITUTE,
     capture_internal_exceptions,
@@ -14,6 +14,7 @@
 from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
+    from collections.abc import MutableMapping
     from typing import Any
 
 
@@ -76,11 +77,9 @@ def send(self, request, **kwargs):
                             key=key, value=value, url=request.url
                         )
                     )
-                    if key == BAGGAGE_HEADER_NAME and request.headers.get(
-                        BAGGAGE_HEADER_NAME
-                    ):
-                        # do not overwrite any existing baggage, just append to it
-                        request.headers[key] += "," + value
+
+                    if key == BAGGAGE_HEADER_NAME:
+                        _add_sentry_baggage_to_headers(request.headers, value)
                     else:
                         request.headers[key] = value
 
@@ -148,3 +147,21 @@ async def send(self, request, **kwargs):
             return rv
 
     AsyncClient.send = send
+
+
+def _add_sentry_baggage_to_headers(headers, sentry_baggage):
+    # type: (MutableMapping[str, str], str) -> None
+    """Add the Sentry baggage to the headers.
+
+    This function directly mutates the provided headers. The provided sentry_baggage
+    is appended to the existing baggage. If the baggage already contains Sentry items,
+    they are stripped out first.
+    """
+    existing_baggage = headers.get(BAGGAGE_HEADER_NAME, "")
+    stripped_existing_baggage = Baggage.strip_sentry_baggage(existing_baggage)
+
+    separator = "," if len(stripped_existing_baggage) > 0 else ""
+
+    headers[BAGGAGE_HEADER_NAME] = (
+        stripped_existing_baggage + separator + sentry_baggage
+    )

sentry_sdk/tracing_utils.py

@@ -609,6 +609,21 @@ def serialize(self, include_third_party=False):
 
         return ",".join(items)
 
+    @staticmethod
+    def strip_sentry_baggage(header):
+        # type: (str) -> str
+        """Remove Sentry baggage from the given header.
+
+        Given a Baggage header, return a new Baggage header with all Sentry baggage items removed.
+        """
+        return ",".join(
+            (
+                item
+                for item in header.split(",")
+                if not Baggage.SENTRY_PREFIX_REGEX.match(item.strip())
+            )
+        )
+
 
 def should_propagate_trace(client, url):
     # type: (sentry_sdk.client.BaseClient, str) -> bool

tests/test_tracing_utils.py

@@ -1,7 +1,7 @@
 from dataclasses import asdict, dataclass
 from typing import Optional, List
 
-from sentry_sdk.tracing_utils import _should_be_included
+from sentry_sdk.tracing_utils import _should_be_included, Baggage
 import pytest
 
 
@@ -94,3 +94,24 @@ def test_should_be_included(test_case, expected):
     kwargs = asdict(test_case)
     kwargs.pop("id")
     assert _should_be_included(**kwargs) == expected
+
+
+@pytest.mark.parametrize(
+    ("header", "expected"),
+    (
+        ("", ""),
+        ("foo=bar", "foo=bar"),
+        (" foo=bar, baz =  qux ", " foo=bar, baz =  qux "),
+        ("sentry-trace_id=123", ""),
+        ("  sentry-trace_id = 123  ", ""),
+        ("sentry-trace_id=123,sentry-public_key=456", ""),
+        ("foo=bar,sentry-trace_id=123", "foo=bar"),
+        ("foo=bar,sentry-trace_id=123,baz=qux", "foo=bar,baz=qux"),
+        (
+            "foo=bar,sentry-trace_id=123,baz=qux,sentry-public_key=456",
+            "foo=bar,baz=qux",
+        ),
+    ),
+)
+def test_strip_sentry_baggage(header, expected):
+    assert Baggage.strip_sentry_baggage(header) == expected