Reduce DB hits for replication

Some streams will occaisonally advance their positions without actually
having any new rows to send over federation. Currently this means that
the token will not advance on the workers, leading to them repeatedly
sending a slightly out of date token. This in turns requires the master
to hit the DB to check if there are any new rows, rather than hitting
the no op logic where we check if the given token matches the current
token.

This commit changes the API to always return an entry if the position
for a stream has changed, allowing workers to advance their tokens
correctly.

2 files changed, 3 insertions, 3 deletions

diff --git a/tests/replication/slave/storage/_base.py b/tests/replication/slave/storage/_base.py
index 1f13cd0bc0..b82868054d 100644
--- a/tests/replication/slave/storage/_base.py
+++ b/tests/replication/slave/storage/_base.py
@@ -42,7 +42,8 @@ class BaseSlavedStoreTestCase(unittest.TestCase):
     @defer.inlineCallbacks
     def replicate(self):
         streams = self.slaved_store.stream_positions()
-        result = yield self.replication.replicate(streams, 100)
+        writer = yield self.replication.replicate(streams, 100)
+        result = writer.finish()
         yield self.slaved_store.process_replication(result)
 
     @defer.inlineCallbacks
diff --git a/tests/replication/test_resource.py b/tests/replication/test_resource.py
index b69832cc1b..f406934a62 100644
--- a/tests/replication/test_resource.py
+++ b/tests/replication/test_resource.py
@@ -120,7 +120,7 @@ class ReplicationResourceCase(unittest.TestCase):
             self.hs.clock.advance_time_msec(1)
             code, body = yield get
             self.assertEquals(code, 200)
-            self.assertEquals(body, {})
+            self.assertEquals(body.get("rows", []), [])
         test_timeout.__name__ = "test_timeout_%s" % (stream)
         return test_timeout
 
@@ -195,7 +195,6 @@ class ReplicationResourceCase(unittest.TestCase):
             self.assertIn("field_names", stream)
             field_names = stream["field_names"]
             self.assertIn("rows", stream)
-            self.assertTrue(stream["rows"])
             for row in stream["rows"]:
                 self.assertEquals(
                     len(row), len(field_names),