call reap on start up and fix under reaping bug

synapse/api/auth.py

@@ -799,7 +799,7 @@ class Auth(object):
             current_mau = yield self.store.get_monthly_active_count()
             if current_mau >= self.hs.config.max_mau_value:
                 raise AuthError(
-                    403, "Monthly Active User Limits AU Limit Exceeded",
+                    403, "Monthly Active User Limit Exceeded",
                     admin_uri=self.hs.config.admin_uri,
                     errcode=Codes.RESOURCE_LIMIT_EXCEED
                 )

synapse/app/homeserver.py

@@ -525,6 +525,7 @@ def run(hs):
     clock.looping_call(
         hs.get_datastore().reap_monthly_active_users, 1000 * 60 * 60
     )
+    yield hs.get_datastore().reap_monthly_active_users()
 
     @defer.inlineCallbacks
     def generate_monthly_active_users():

synapse/storage/monthly_active_users.py

@@ -96,7 +96,10 @@ class MonthlyActiveUsersStore(SQLBaseStore):
             # While Postgres does not require 'LIMIT', but also does not support
             # negative LIMIT values. So there is no way to write it that both can
             # support
-            query_args = [self.hs.config.max_mau_value]
+            safe_guard = self.hs.config.max_mau_value - len(self.reserved_users)
+            # Must be greater than zero for postgres
+            safe_guard = safe_guard if safe_guard > 0 else 0
+            query_args = [safe_guard]
 
             base_sql = """
                 DELETE FROM monthly_active_users

tests/storage/test_monthly_active_users.py

@@ -75,6 +75,19 @@ class MonthlyActiveUsersTestCase(tests.unittest.TestCase):
         active_count = yield self.store.get_monthly_active_count()
         self.assertEquals(active_count, user_num)
 
+        # Test that regalar users are removed from the db
+        ru_count = 2
+        yield self.store.upsert_monthly_active_user("@ru1:server")
+        yield self.store.upsert_monthly_active_user("@ru2:server")
+        active_count = yield self.store.get_monthly_active_count()
+
+        self.assertEqual(active_count, user_num + ru_count)
+        self.hs.config.max_mau_value = user_num
+        yield self.store.reap_monthly_active_users()
+
+        active_count = yield self.store.get_monthly_active_count()
+        self.assertEquals(active_count, user_num)
+
     @defer.inlineCallbacks
     def test_can_insert_and_count_mau(self):
         count = yield self.store.get_monthly_active_count()