1 files changed, 34 insertions, 1 deletions
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index 6f235ac051..11a1b942f1 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -85,6 +85,7 @@ class BackgroundUpdateStore(SQLBaseStore):
         self._background_update_performance = {}
         self._background_update_queue = []
         self._background_update_handlers = {}
+        self._all_done = False
 
     @defer.inlineCallbacks
     def start_doing_background_updates(self):
@@ -106,9 +107,41 @@ class BackgroundUpdateStore(SQLBaseStore):
                         "No more background updates to do."
                         " Unscheduling background update task."
                     )
+                    self._all_done = True
                     defer.returnValue(None)
 
     @defer.inlineCallbacks
+    def has_completed_background_updates(self):
+        """Check if all the background updates have completed
+
+        Returns:
+            Deferred[bool]: True if all background updates have completed
+        """
+        # if we've previously determined that there is nothing left to do, that
+        # is easy
+        if self._all_done:
+            defer.returnValue(True)
+
+        # obviously, if we have things in our queue, we're not done.
+        if self._background_update_queue:
+            defer.returnValue(False)
+
+        # otherwise, check if there are updates to be run. This is important,
+        # as we may be running on a worker which doesn't perform the bg updates
+        # itself, but still wants to wait for them to happen.
+        updates = yield self._simple_select_onecol(
+            "background_updates",
+            keyvalues=None,
+            retcol="1",
+            desc="check_background_updates",
+        )
+        if not updates:
+            self._all_done = True
+            defer.returnValue(True)
+
+        defer.returnValue(False)
+
+    @defer.inlineCallbacks
     def do_next_background_update(self, desired_duration_ms):
         """Does some amount of work on the next queued background update
 
@@ -269,7 +302,7 @@ class BackgroundUpdateStore(SQLBaseStore):
             # Sqlite doesn't support concurrent creation of indexes.
             #
             # We don't use partial indices on SQLite as it wasn't introduced
-            # until 3.8, and wheezy has 3.7
+            # until 3.8, and wheezy and CentOS 7 have 3.7
             #
             # We assume that sqlite doesn't give us invalid indices; however
             # we may still end up with the index existing but the