Ensure that lambda headers are always a dict

CHANGELOG.asciidoc

@@ -42,6 +42,7 @@ endif::[]
 ===== Bug fixes
 
 * Fix url argument fetching in aiohttp_client instrumentation {pull}1890[#1890]
+* Fix a bug in the AWS Lambda instrumentation when `event["headers"] is None` {pull}1907[#1907]
 
 
 

elasticapm/contrib/serverless/aws.py

@@ -162,7 +162,7 @@ def __enter__(self):
  # service like Step Functions, and is unlikely to be standardized
  # in any way. We just have to rely on our defaults in this case.
  self.event = {}
- trace_parent = TraceParent.from_headers(self.event.get("headers", {}))
+ trace_parent = TraceParent.from_headers(self.event.get("headers") or {})
 
  global COLD_START
  cold_start = COLD_START
@@ -525,7 +525,7 @@ def get_url_dict(event: dict) -> dict:
  """
  Reconstruct URL from API Gateway
  """
- headers = event.get("headers", {})
+ headers = event.get("headers") or {}
  protocol = headers.get("X-Forwarded-Proto", headers.get("x-forwarded-proto", "https"))
  host = headers.get("Host", headers.get("host", ""))
  stage = nested_key(event, "requestContext", "stage") or ""

tests/contrib/serverless/aws_tests.py

@@ -455,3 +455,18 @@ def test_func(event, context):
  assert b"metadata" in request.data
  assert b"transaction" in request.data
  sending_elasticapm_client.close()
+
+
+def test_with_headers_as_none(event_api2, context, elasticapm_client):
+ os.environ["AWS_LAMBDA_FUNCTION_NAME"] = "test_func"
+
+ @capture_serverless
+ def test_func(event, context):
+ with capture_span("test_span"):
+ time.sleep(0.01)
+ return {"statusCode": 200, "headers": {"foo": "bar"}}
+
+ event_api2["headers"] = None
+
+ test_func(event_api2, context)
+ assert len(elasticapm_client.events[constants.TRANSACTION]) == 1