Fix Prometheus metrics being negative (mixed up start/end) (#13584)

Fix:

 - https://github.com/matrix-org/synapse/pull/13535#discussion_r949582508
 - https://github.com/matrix-org/synapse/pull/13533#discussion_r949577244

1 files changed, 5 insertions, 1 deletions

diff --git a/synapse/rest/client/room.py b/synapse/rest/client/room.py

index 0eafbae457..3259de4802 100644
--- a/synapse/rest/client/room.py
+++ b/synapse/rest/client/room.py
@@ -116,9 +116,13 @@ messsages_response_timer = Histogram(
         2.5,
         5.0,
         10.0,
+        20.0,
         30.0,
         60.0,
+        80.0,
+        100.0,
         120.0,
+        150.0,
         180.0,
         "+Inf",
     ),
@@ -674,7 +678,7 @@ class RoomMessageListRestServlet(RestServlet):
         room_member_count = await make_deferred_yieldable(room_member_count_deferred)
         messsages_response_timer.labels(
             room_size=_RoomSize.from_member_count(room_member_count)
-        ).observe((processing_start_time - processing_end_time) / 1000)
+        ).observe((processing_end_time - processing_start_time) / 1000)
 
         return 200, msgs