Update Flip.select_channels() to sort channels by last_notify_duration

If a check has multiple associated channels, some are slow and
some are quick, handle the quick ones first.

hc/api/models.py

@@ -1173,6 +1173,7 @@ class Flip(models.Model):
         * Exclude all channels for new->up and paused->up transitions.
         * Exclude disabled channels
         * Exclude channels where transport.is_noop(status) returns True
+        * Sort channels by last_notify_duration (shorter durations first)
         """
 
         # Don't send alerts on new->up and paused->up transitions
@@ -1183,6 +1184,7 @@ class Flip(models.Model):
             raise NotImplementedError(f"Unexpected status: {self.new_status}")
 
         q = self.owner.channel_set.exclude(disabled=True)
+        q = q.order_by("last_notify_duration")
         return [ch for ch in q if not ch.transport.is_noop(self.new_status)]
 
 

hc/api/tests/test_flip_model.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import json
+from datetime import timedelta as td
 
 from django.utils.timezone import now
 
@@ -51,3 +52,16 @@ class FlipModelTestCase(BaseTestCase):
 
         channels = self.flip.select_channels()
         self.assertEqual(channels, [])
+
+    def test_it_sorts_channels_by_last_notify_duration(self) -> None:
+        c1 = Channel.objects.create(
+            project=self.project, kind="email", last_notify_duration=td(seconds=1)
+        )
+        c1.checks.add(self.check)
+        c9 = Channel.objects.create(
+            project=self.project, kind="email", last_notify_duration=td(seconds=9)
+        )
+        c9.checks.add(self.check)
+
+        channels = self.flip.select_channels()
+        self.assertEqual(channels, [c1, c9, self.channel])