From ca9bc1f4feaaabce48595ee2e387529f5bd365e6 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Tue, 7 Aug 2018 10:00:03 +0100
Subject: [PATCH] Fix occasional glitches in the
 synapse_event_persisted_position metric

Every so often this metric glitched to a negative number. I'm assuming it was
due to backfilled events.
---
 synapse/storage/events.py | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index e8e5a0fe4..ce32e8fef 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -485,9 +485,14 @@ class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore
                     new_forward_extremeties=new_forward_extremeties,
                 )
                 persist_event_counter.inc(len(chunk))
-                synapse.metrics.event_persisted_position.set(
-                    chunk[-1][0].internal_metadata.stream_ordering,
-                )
+
+                if not backfilled:
+                    # backfilled events have negative stream orderings, so we don't
+                    # want to set the event_persisted_position to that.
+                    synapse.metrics.event_persisted_position.set(
+                        chunk[-1][0].internal_metadata.stream_ordering,
+                    )
+
                 for event, context in chunk:
                     if context.app_service:
                         origin_type = "local"