Fix federation inbound age metric. (#10355)

erikjohnston · web-flow · commit 879d8c1ee170 · 2021-07-13T11:33:15.000+01:00
We should be reporting the age rather than absolute timestamp.
diff --git a/changelog.d/10355.bugfix b/changelog.d/10355.bugfix
@@ -0,0 +1 @@
+Fix newly added `synapse_federation_server_oldest_inbound_pdu_in_staging` prometheus metric to measure age rather than timestamp.
diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py
@@ -1230,7 +1230,9 @@ def _get_stats_for_federation_staging_txn(txn):
                 "SELECT coalesce(min(received_ts), 0) FROM federation_inbound_events_staging"
             )
 
-            (age,) = txn.fetchone()
+            (received_ts,) = txn.fetchone()
+
+            age = self._clock.time_msec() - received_ts
 
             return count, age
 

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+Fix newly added `synapse_federation_server_oldest_inbound_pdu_in_staging` prometheus metric to measure age rather than timestamp.
Original file line number	Diff line number	Diff line change
`@@ -1230,7 +1230,9 @@ def _get_stats_for_federation_staging_txn(txn):`
`1230`	`1230`	`"SELECT coalesce(min(received_ts), 0) FROM federation_inbound_events_staging"`
`1231`	`1231`	`)`
`1232`	`1232`
`1233`		`- (age,) = txn.fetchone()`
	`1233`	`+ (received_ts,) = txn.fetchone()`
	`1234`	`+`
	`1235`	`+ age = self._clock.time_msec() - received_ts`
`1234`	`1236`
`1235`	`1237`	`return count, age`
`1236`	`1238`