Fix bug in retrieve_task_id that fails to check the body for the task…

… id when headers has data (but no task id), which wrongly kept spans open.

ddtrace/contrib/internal/celery/utils.py

@@ -128,9 +128,12 @@ def retrieve_task_id(context):
     """
     headers = context.get("headers")
     body = context.get("body")
-    if headers:
+    # Check if the id is in the headers, then check the body for it.
+    # If we don't check the id first, we could wrongly assume no task_id
+    # when the task_id is in the body.
+    if headers and 'id' in headers:
         # Protocol Version 2 (default from Celery 4.0)
         return headers.get("id")
-    else:
+    elif body and 'id' in body:
         # Protocol Version 1
         return body.get("id")

releasenotes/notes/fix-protocol-check-62ad7d096b1f36a9.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    tracing(celery): Fixes an issue where ``celery.apply`` spans using protocol 1 didn't close by improving the check for the task id in the body.