Move delta from +10% to -10%

synapse/config/registration.py

@@ -132,7 +132,7 @@ class RegistrationConfig(Config):
         # then derive an expiration date from the current validity period), and some time
         # after that the validity period changes and Synapse is restarted, the users'
         # expiration dates won't be updated unless their account is manually renewed. This
-        # date will be randomly selected within a range [now + period ; now + period + d],
+        # date will be randomly selected within a range [now + period - d ; now + period],
         # where d is equal to 10%% of the validity period.
         #
         #account_validity:

synapse/storage/_base.py

@@ -329,7 +329,7 @@ class SQLBaseStore(object):
              user_id (str): User ID to set an expiration date for.
              use_delta (bool): If set to False, the expiration date for the user will be
                 now + validity period. If set to True, this expiration date will be a
-                random value in the [now + period; now + period + d] range, d being a
+                random value in the [now + period - d ; now + period] range, d being a
                 delta equal to 10% of the validity period.
         """
         now_ms = self._clock.time_msec()
@@ -337,8 +337,8 @@ class SQLBaseStore(object):
 
         if use_delta:
             expiration_ts = self.rand.randrange(
+                expiration_ts - self._account_validity.startup_job_max_delta,
                 expiration_ts,
-                expiration_ts + self._account_validity.startup_job_max_delta,
             )
 
         self._simple_insert_txn(

tests/rest/client/v2_alpha/test_register.py

@@ -467,5 +467,5 @@ class AccountValidityBackgroundJobTestCase(unittest.HomeserverTestCase):
 
         res = self.get_success(self.store.get_expiration_ts_for_user(user_id))
 
-        self.assertLessEqual(res, now_ms + self.validity_period + self.max_delta)
-        self.assertGreaterEqual(res, now_ms + self.validity_period)
+        self.assertGreaterEqual(res, now_ms + self.validity_period - self.max_delta)
+        self.assertLessEqual(res, now_ms + self.validity_period)