chore: investigate delivery report (#17684)

* chore: investigate delivery report

* async always leaks... try event

posthog/utils.py

@@ -10,6 +10,7 @@
 import secrets
 import string
 import subprocess
+import threading
 import time
 import uuid
 import zlib
@@ -1192,10 +1193,22 @@ def wait_for_parallel_celery_group(task: Any, max_timeout: Optional[datetime.tim
 
     start_time = timezone.now()
 
-    while not task.ready():
-        if timezone.now() - start_time > max_timeout:
-            raise TimeoutError("Timed out waiting for celery task to finish")
-        time.sleep(0.1)
+    event = threading.Event()
+
+    while not event.is_set():
+        if task.ready():
+            event.set()
+        else:
+            if timezone.now() - start_time > max_timeout:
+                logger.error(
+                    "Timed out waiting for celery task to finish",
+                    methods=dir(task),
+                    task=task,
+                    timeout=max_timeout,
+                    start_time=start_time,
+                )
+                raise TimeoutError("Timed out waiting for celery task to finish")
+            event.wait(0.1)
     return task