Checker: Make safety margin for scheduling configurable

As a workaround for services with a high variance in check runtimes.

Closes: #79

Co-authored-by: Simon Ruderich <simon@ruderich.org>

src/ctf_gameserver/checker/database.py

@@ -42,6 +42,21 @@ def get_service_attributes(db_conn, service_slug, prohibit_changes=False):
     }
 
 
+def get_service_margin(db_conn, service_slug, prohibit_changes=False):
+    """
+    Returns the configured safety margin of a service for a given slug.
+    """
+
+    with transaction_cursor(db_conn, prohibit_changes) as cursor:
+        cursor.execute('SELECT margin FROM scoring_service WHERE slug = %s', (service_slug,))
+        result = cursor.fetchone()
+
+    if result is None:
+        raise DBDataError('Service has not been configured')
+
+    return result[0]
+
+
 def get_current_tick(db_conn, prohibit_changes=False):
     """
     Reads the current tick and the "cancel_checks" field from the game database.

src/ctf_gameserver/checker/master.py

@@ -143,6 +143,7 @@ def main():
         try:
             service_id = database.get_service_attributes(db_conn, args.service,
                                                          prohibit_changes=True)['id']
+            database.get_service_margin(db_conn, args.service, prohibit_changes=True)
         except DBDataError as e:
             logging.warning('Invalid database state: %s', e)
             service_id = 1337    # Use dummy value for subsequent grant checks
@@ -392,7 +393,7 @@ def update_launch_params(self, tick):
         total_tasks = database.get_task_count(self.db_conn, self.service['id'])
         local_tasks = math.ceil(total_tasks / self.checker_count)
 
-        margin_seconds = self.tick_duration.total_seconds() / 6
+        margin_seconds = database.get_service_margin(self.db_conn, self.service['slug'])
         launch_timeframe = max(self.tick_duration.total_seconds() - check_duration - margin_seconds, 0)
 
         intervals_per_timeframe = math.floor(launch_timeframe / self.interval) + 1

src/ctf_gameserver/web/scoring/models.py

@@ -13,6 +13,10 @@ class Service(models.Model):
 
     name = models.CharField(max_length=30, unique=True)
     slug = models.SlugField(max_length=30, unique=True, help_text=_('Simplified name for use in paths'))
+    margin = models.PositiveIntegerField(default=30,
+                                         help_text=_('Safety margin (in seconds) for checker scheduling, '
+                                                     'gets added to the automatically determined check '
+                                                     'duration'))
 
     def __str__(self):    # pylint: disable=invalid-str-returned
         return self.name

tests/checker/test_master.py

@@ -172,4 +172,4 @@ def test_update_launch_params(self, check_duration_mock):
         self.master_loop.interval = 10
         self.master_loop.tick_duration = datetime.timedelta(seconds=90)
         self.master_loop.update_launch_params(10)
-        self.assertEqual(self.master_loop.tasks_per_launch, 7)
+        self.assertEqual(self.master_loop.tasks_per_launch, 9)