Fix issue on older celery versions

newrelic/hooks/application_celery.py

@@ -99,7 +99,11 @@ def _application():
             with BackgroundTask(_application(), _name, "Celery", source=instance) as transaction:
                 # Attempt to grab distributed tracing headers
                 try:
-                    headers = wrapped.request.headers
+                    # Headers on earlier versions of Celery may end up as attributes
+                    # on the request context instead of as custom headers. Handler this
+                    # by defaulting to using vars() if headers is not available
+                    headers = getattr(wrapped.request, "headers", None) or vars(wrapped.request)
+
                     settings = transaction.settings
                     if headers is not None and settings is not None:
                         if settings.distributed_tracing.enabled:
@@ -179,7 +183,7 @@ def wrap_Celery_send_task(wrapped, instance, args, kwargs):
     if dt_headers:
         if "headers" not in kwargs or not original_headers:
             kwargs["headers"] = dict(dt_headers)
-        elif hasattr(original_headers, "items"):
+        else:
             kwargs["headers"] = dt_headers = dict(dt_headers)
             dt_headers.update(dict(original_headers))
 

tests/application_celery/test_celery.py

@@ -78,8 +78,8 @@ def test_celery_tasks_ignore_transaction():
     No transaction is recorded, due to the call to ignore_transaction(),
     so no validation fixture is used. The purpose of this test is to make
     sure the agent doesn't throw an error.
-
     """
+
     add_result = add(1, 2)
     assert add_result == 3
 
@@ -99,8 +99,8 @@ def test_celery_tasks_end_transaction():
     """
     Only functions that run before the call to end_of_transaction() are
     included in the transaction.
-
     """
+
     add_result = add(1, 2)
     assert add_result == 3
 
@@ -119,7 +119,10 @@ def test_celery_tasks_end_transaction():
 @validate_transaction_count(1)
 @validate_code_level_metrics("_target_application", "nested_add")
 def test_celery_nested_tasks():
-    """ """
-
+    """
+    Celery tasks run inside other celery tasks should not start a new transactions,
+    and should create a function trace instead.
+    """
+
     add_result = nested_add(1, 2)
     assert add_result == 3