hub: tick delay fix (#1587)

* hub: tick delay fix

todo and timer callbacks can perform actions that
require a tick callback to be executed right away
without polling.

the current order can cause issues
when using single worker with no prefetch (acks late).

related issue in celery:
https://github.com/celery/celery/issues/7718

* add unit test for hub delay fix

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

2 files changed, 22 insertions, 4 deletions

diff --git a/kombu/asynchronous/hub.py b/kombu/asynchronous/hub.py
index 14d25b93..e5b1163c 100644
--- a/kombu/asynchronous/hub.py
+++ b/kombu/asynchronous/hub.py
@@ -300,14 +300,15 @@ class Hub:
         while 1:
             todo = self._pop_ready()
 
-            for tick_callback in on_tick:
-                tick_callback()
-
             for item in todo:
                 if item:
                     item()
 
             poll_timeout = fire_timers(propagate=propagate) if scheduled else 1
+
+            for tick_callback in on_tick:
+                tick_callback()
+
             #  print('[[[HUB]]]: %s' % (self.repr_active(),))
             if readers or writers:
                 to_consolidate = []
diff --git a/t/unit/asynchronous/test_hub.py b/t/unit/asynchronous/test_hub.py
index bcbbb260..27b048b9 100644
--- a/t/unit/asynchronous/test_hub.py
+++ b/t/unit/asynchronous/test_hub.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import errno
-from unittest.mock import Mock, call, patch
+from unittest.mock import ANY, Mock, call, patch
 
 import pytest
 from vine import promise
@@ -542,6 +542,23 @@ class test_Hub:
         callbacks[1].assert_called_once_with()
         deferred.assert_not_called()
 
+    def test_loop__no_todo_tick_delay(self):
+        cb = Mock(name='parent')
+        cb.todo, cb.tick, cb.poller = Mock(), Mock(), Mock()
+        cb.poller.poll.side_effect = lambda obj: ()
+        self.hub.poller = cb.poller
+        self.hub.add(2, Mock(), READ)
+        self.hub.call_soon(cb.todo)
+        self.hub.on_tick = [cb.tick]
+
+        next(self.hub.loop)
+
+        cb.assert_has_calls([
+            call.todo(),
+            call.tick(),
+            call.poller.poll(ANY),
+        ])
+
     def test__pop_ready_pops_ready_items(self):
         self.hub._ready.add(None)
         ret = self.hub._pop_ready()