Rename 'populate_stats_process_rooms_2' background job back to 'populate_stats_process_rooms' again (#8243)

Fixes https://github.com/matrix-org/synapse/issues/8238

Alongside the delta file, some changes were also necessary to the codebase to remove references to the now defunct `populate_stats_process_rooms_2` background job. Thankfully the latter doesn't seem to have made it into any documentation yet :)

changelog.d/8243.misc

@@ -0,0 +1 @@
+Remove the 'populate_stats_process_rooms_2' background job and restore functionality to 'populate_stats_process_rooms'.

synapse/storage/databases/main/schema/delta/58/16populate_stats_process_rooms_fix.sql

@@ -0,0 +1,22 @@
+/* Copyright 2020 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+-- This delta file fixes a regression introduced by 58/12room_stats.sql, removing the hacky
+-- populate_stats_process_rooms_2 background job and restores the functionality under the
+-- original name.
+-- See https://github.com/matrix-org/synapse/issues/8238 for details
+
+DELETE FROM background_updates WHERE update_name = 'populate_stats_process_rooms';
+UPDATE background_updates SET update_name = 'populate_stats_process_rooms'
+    WHERE update_name = 'populate_stats_process_rooms_2';

synapse/storage/databases/main/stats.py

@@ -73,9 +73,6 @@ class StatsStore(StateDeltasStore):
         self.db_pool.updates.register_background_update_handler(
             "populate_stats_process_rooms", self._populate_stats_process_rooms
         )
-        self.db_pool.updates.register_background_update_handler(
-            "populate_stats_process_rooms_2", self._populate_stats_process_rooms_2
-        )
         self.db_pool.updates.register_background_update_handler(
             "populate_stats_process_users", self._populate_stats_process_users
         )
@@ -148,31 +145,10 @@ class StatsStore(StateDeltasStore):
         return len(users_to_work_on)
 
     async def _populate_stats_process_rooms(self, progress, batch_size):
-        """
-        This was a background update which regenerated statistics for rooms.
-
-        It has been replaced by StatsStore._populate_stats_process_rooms_2. This background
-        job has been scheduled to run as part of Synapse v1.0.0, and again now. To ensure
-        someone upgrading from <v1.0.0, this background task has been turned into a no-op
-        so that the potentially expensive task is not run twice.
-
-        Further context: https://github.com/matrix-org/synapse/pull/7977
-        """
-        await self.db_pool.updates._end_background_update(
-            "populate_stats_process_rooms"
-        )
-        return 1
-
-    async def _populate_stats_process_rooms_2(self, progress, batch_size):
-        """
-        This is a background update which regenerates statistics for rooms.
-
-        It replaces StatsStore._populate_stats_process_rooms. See its docstring for the
-        reasoning.
-        """
+        """This is a background update which regenerates statistics for rooms."""
         if not self.stats_enabled:
             await self.db_pool.updates._end_background_update(
-                "populate_stats_process_rooms_2"
+                "populate_stats_process_rooms"
             )
             return 1
 
@@ -189,13 +165,13 @@ class StatsStore(StateDeltasStore):
             return [r for r, in txn]
 
         rooms_to_work_on = await self.db_pool.runInteraction(
-            "populate_stats_rooms_2_get_batch", _get_next_batch
+            "populate_stats_rooms_get_batch", _get_next_batch
         )
 
         # No more rooms -- complete the transaction.
         if not rooms_to_work_on:
             await self.db_pool.updates._end_background_update(
-                "populate_stats_process_rooms_2"
+                "populate_stats_process_rooms"
             )
             return 1
 
@@ -204,9 +180,9 @@ class StatsStore(StateDeltasStore):
             progress["last_room_id"] = room_id
 
         await self.db_pool.runInteraction(
-            "_populate_stats_process_rooms_2",
+            "_populate_stats_process_rooms",
             self.db_pool.updates._background_update_progress_txn,
-            "populate_stats_process_rooms_2",
+            "populate_stats_process_rooms",
             progress,
         )
 

tests/handlers/test_stats.py

@@ -54,7 +54,7 @@ class StatsRoomTests(unittest.HomeserverTestCase):
             self.store.db_pool.simple_insert(
                 "background_updates",
                 {
-                    "update_name": "populate_stats_process_rooms_2",
+                    "update_name": "populate_stats_process_rooms",
                     "progress_json": "{}",
                     "depends_on": "populate_stats_prepare",
                 },
@@ -66,7 +66,7 @@ class StatsRoomTests(unittest.HomeserverTestCase):
                 {
                     "update_name": "populate_stats_process_users",
                     "progress_json": "{}",
-                    "depends_on": "populate_stats_process_rooms_2",
+                    "depends_on": "populate_stats_process_rooms",
                 },
             )
         )
@@ -219,10 +219,7 @@ class StatsRoomTests(unittest.HomeserverTestCase):
         self.get_success(
             self.store.db_pool.simple_insert(
                 "background_updates",
-                {
-                    "update_name": "populate_stats_process_rooms_2",
-                    "progress_json": "{}",
-                },
+                {"update_name": "populate_stats_process_rooms", "progress_json": "{}"},
             )
         )
         self.get_success(
@@ -231,7 +228,7 @@ class StatsRoomTests(unittest.HomeserverTestCase):
                 {
                     "update_name": "populate_stats_cleanup",
                     "progress_json": "{}",
-                    "depends_on": "populate_stats_process_rooms_2",
+                    "depends_on": "populate_stats_process_rooms",
                 },
             )
         )
@@ -728,7 +725,7 @@ class StatsRoomTests(unittest.HomeserverTestCase):
             self.store.db_pool.simple_insert(
                 "background_updates",
                 {
-                    "update_name": "populate_stats_process_rooms_2",
+                    "update_name": "populate_stats_process_rooms",
                     "progress_json": "{}",
                     "depends_on": "populate_stats_prepare",
                 },
@@ -740,7 +737,7 @@ class StatsRoomTests(unittest.HomeserverTestCase):
                 {
                     "update_name": "populate_stats_process_users",
                     "progress_json": "{}",
-                    "depends_on": "populate_stats_process_rooms_2",
+                    "depends_on": "populate_stats_process_rooms",
                 },
             )
         )