Allow custom back off functions

tubesync/common/huey.py

@@ -65,15 +65,29 @@ def exponential_backoff(task_func=None, /, *args, **kwargs):
     if task_func is None:
         from django_huey import task as huey_task
         task_func = huey_task
-    def backoff(attempt, /):
+    backoff_func = kwargs.pop('backoff_func', None)
+    def default_backoff(attempt, /):
         return (5+(attempt**4))
+    if backoff_func is None or not callable(backoff_func):
+        backoff_func = default_backoff
     def deco(fn):
         @wraps(fn)
         def inner(*a, **kwa):
-            task = kwa.pop('task')
+            backoff = backoff_func
+            # the scoping becomes complicated when reusing functions
+            try:
+                _task = kwa.pop('task')
+            except KeyError:
+                pass
+            else:
+                task = _task
             try:
                 return fn(*a, **kwa)
             except Exception as exc:
+                try:
+                    task is not None
+                except NameError:
+                    raise exc
                 for attempt in range(1, 240):
                     if backoff(attempt) > task.retry_delay:
                         task.retry_delay = backoff(attempt)
@@ -84,7 +98,7 @@ def exponential_backoff(task_func=None, /, *args, **kwargs):
                 raise exc
         kwargs.update(dict(
             context=True,
-            retry_delay=backoff(1),
+            retry_delay=backoff_func(1),
         ))
         return task_func(*args, **kwargs)(inner)
     return deco