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opentelemetry-instrumentation-aws-lambda: fix improper handling of header casing #4216

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9ac64fc
opentelemetry-instrumentation-aws-lambda: fix improper handling of he…
herin049 Feb 19, 2026
b3d7ab0
update CHANGELOG.md
herin049 Feb 19, 2026
4409fb3
add CIDict
herin049 Feb 21, 2026
7ab4d42
update CHANGELOG.md
herin049 Feb 21, 2026
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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
([#4078](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4171))
- `opentelemetry-instrumentation-aiohttp-server`: fix HTTP error inconsistencies
([#4175](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4175))
- `opentelemetry-instrumentation-aws-lambda`, `opentelemetry-instrumentation`: fix improper handling of header casing
([#4216](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4216))

### Breaking changes

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18 changes: 11 additions & 7 deletions ...metry-instrumentation-aws-lambda/src/opentelemetry/instrumentation/aws_lambda/__init__.py
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Expand Up @@ -84,6 +84,7 @@ def custom_event_context_extractor(lambda_event):
from opentelemetry.context.context import Context
from opentelemetry.instrumentation.aws_lambda.package import _instruments
from opentelemetry.instrumentation.aws_lambda.version import __version__
from opentelemetry.instrumentation.cidict import CIDict
from opentelemetry.instrumentation.instrumentor import BaseInstrumentor
from opentelemetry.instrumentation.utils import unwrap
from opentelemetry.metrics import MeterProvider, get_meter_provider
Expand Down Expand Up @@ -176,7 +177,9 @@ def _default_event_context_extractor(lambda_event: Any) -> Context:
)
if not isinstance(headers, dict):
headers = {}
return get_global_textmap().extract(headers)
return get_global_textmap().extract(
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@xrmx xrmx Feb 20, 2026 •
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When I did this in another code base I've only done the header normalization for v1 using this to decide if that was the case:

def should_normalize(event):
    request_context = event.get("requestContext", {})
    return ("elb" in request_context or "requestId" in request_context) and "http" not in request_context

Maybe here it would be impractical since we are picking more stuff from the headers.

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@herin049 herin049 Feb 21, 2026

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We'd want to normalize regardless, no? For example, even if you're using API GW v2, it's possible that a caller still might not provide headers as lowercase.

CIDict(headers),
)


def _determine_parent_context(
Expand Down Expand Up @@ -216,20 +219,21 @@ def _set_api_gateway_v1_proxy_attributes(
span.set_attribute(HTTP_METHOD, lambda_event.get("httpMethod"))

if lambda_event.get("headers"):
if "User-Agent" in lambda_event["headers"]:
headers = CIDict(lambda_event["headers"])
if "User-Agent" in headers:
span.set_attribute(
HTTP_USER_AGENT,
lambda_event["headers"]["User-Agent"],
headers["User-Agent"],
)
if "X-Forwarded-Proto" in lambda_event["headers"]:
if "X-Forwarded-Proto" in headers:
span.set_attribute(
HTTP_SCHEME,
lambda_event["headers"]["X-Forwarded-Proto"],
headers["X-Forwarded-Proto"],
)
if "Host" in lambda_event["headers"]:
if "Host" in headers:
span.set_attribute(
NET_HOST_NAME,
lambda_event["headers"]["Host"],
headers["Host"],
)
if "resource" in lambda_event:
span.set_attribute(HTTP_ROUTE, lambda_event["resource"])
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81 changes: 81 additions & 0 deletions .../opentelemetry-instrumentation-aws-lambda/tests/test_aws_lambda_instrumentation_manual.py
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Expand Up @@ -325,6 +325,36 @@ def custom_event_context_extractor(lambda_event):
expected_baggage=MOCK_W3C_BAGGAGE_VALUE,
propagators="tracecontext,baggage",
),
TestCase(
name="case_insensitive_headers_uppercase",
custom_extractor=None,
context={
"headers": {
TraceContextTextMapPropagator._TRACEPARENT_HEADER_NAME.upper(): MOCK_W3C_TRACE_CONTEXT_SAMPLED,
TraceContextTextMapPropagator._TRACESTATE_HEADER_NAME.upper(): f"{MOCK_W3C_TRACE_STATE_KEY}={MOCK_W3C_TRACE_STATE_VALUE},foo=1,bar=2",
}
},
expected_traceid=MOCK_W3C_TRACE_ID,
expected_parentid=MOCK_W3C_PARENT_SPAN_ID,
expected_trace_state_len=3,
expected_state_value=MOCK_W3C_TRACE_STATE_VALUE,
xray_traceid=MOCK_XRAY_TRACE_CONTEXT_NOT_SAMPLED,
),
TestCase(
name="case_insensitive_headers_mixedcase",
custom_extractor=None,
context={
"headers": {
"TraceParent": MOCK_W3C_TRACE_CONTEXT_SAMPLED,
"tRaCeStAtE": f"{MOCK_W3C_TRACE_STATE_KEY}={MOCK_W3C_TRACE_STATE_VALUE},foo=1,bar=2",
}
},
expected_traceid=MOCK_W3C_TRACE_ID,
expected_parentid=MOCK_W3C_PARENT_SPAN_ID,
expected_trace_state_len=3,
expected_state_value=MOCK_W3C_TRACE_STATE_VALUE,
xray_traceid=MOCK_XRAY_TRACE_CONTEXT_NOT_SAMPLED,
),
]
for test in tests:
with self.subTest(test_name=test.name):
Expand Down Expand Up @@ -400,6 +430,57 @@ def test_lambda_no_error_with_invalid_flush_timeout(self):

test_env_patch.stop()

def test_api_gateway_v1_attributes_case_insensitivity(self):
AwsLambdaInstrumentor().instrument()

mock_execute_lambda(
{
"httpMethod": "GET",
"headers": {
"user-agent": "lowercase-agent",
"host": "lowercase-host",
"x-forwarded-proto": "http",
},
"resource": "/test",
"requestContext": {
"version": "1.0",
},
}
)

spans = self.memory_exporter.get_finished_spans()
self.assertEqual(len(spans), 1)
span = spans[0]
self.assertEqual(
span.attributes.get(HTTP_USER_AGENT), "lowercase-agent"
)
self.assertEqual(span.attributes.get(NET_HOST_NAME), "lowercase-host")
self.assertEqual(span.attributes.get(HTTP_SCHEME), "http")

self.memory_exporter.clear()

mock_execute_lambda(
{
"httpMethod": "GET",
"headers": {
"uSeR-aGeNt": "mixed-agent",
"hOsT": "mixed-host",
"X-fOrWaRdEd-PrOtO": "https",
},
"resource": "/test",
"requestContext": {
"version": "1.0",
},
}
)

spans = self.memory_exporter.get_finished_spans()
self.assertEqual(len(spans), 1)
span = spans[0]
self.assertEqual(span.attributes.get(HTTP_USER_AGENT), "mixed-agent")
self.assertEqual(span.attributes.get(NET_HOST_NAME), "mixed-host")
self.assertEqual(span.attributes.get(HTTP_SCHEME), "https")

def test_lambda_handles_multiple_consumers(self):
test_env_patch = mock.patch.dict(
"os.environ",
Expand Down
93 changes: 93 additions & 0 deletions opentelemetry-instrumentation/src/opentelemetry/instrumentation/cidict.py
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@@ -0,0 +1,93 @@
# Copyright The OpenTelemetry Authors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from __future__ import annotations

from typing import (
Any,
Generic,
Iterable,
Iterator,
Mapping,
MutableMapping,
Optional,
Tuple,
TypeVar,
Union,
)

KT = TypeVar("KT")
VT = TypeVar("VT")


class CIDict(MutableMapping[KT, VT], Generic[KT, VT]):
def __init__(
self,
data: Optional[Union[Mapping[KT, VT], Iterable[Tuple[KT, VT]]]] = None,
) -> None:
self._data: dict[KT, Tuple[KT, VT]] = {}
if data is None:
data = {}
self.update(data)

@staticmethod
def _normalize_key(key: KT) -> KT:
if isinstance(key, str):
return key.lower() # type: ignore
return key

def _get_entry(self, key: KT) -> Tuple[KT, VT]:
normalized_key = self._normalize_key(key)
if normalized_key in self._data:
return self._data[normalized_key]
raise KeyError(repr(key))

def original_key(self, key: KT) -> KT:
return self._get_entry(key)[0]

def normalized_items(self) -> Iterable[Tuple[KT, VT]]:
return ((key, value[1]) for key, value in self._data.items())

def __setitem__(self, key: KT, value: VT, /) -> None:
self._data[self._normalize_key(key)] = (key, value)

def __delitem__(self, key: KT, /) -> None:
try:
del self._data[self._normalize_key(key)]
except KeyError:
raise KeyError(repr(key)) from None

def __getitem__(self, key: KT, /) -> VT:
return self._get_entry(key)[1]

def __len__(self) -> int:
return len(self._data)

def __iter__(self) -> Iterator[KT]:
return (key for key, _ in self._data.values())

def __repr__(self) -> str:
return f"{self.__class__.__name__}({dict(self.items())!r})"

def __eq__(self, other: Any) -> bool:
if isinstance(other, CIDict):
return dict(self.normalized_items()) == dict(
other.normalized_items()
)
if not isinstance(other, Mapping):
return False
ciother: CIDict[Any, Any] = CIDict(other)
return dict(self.normalized_items()) == dict(
ciother.normalized_items()
)
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