From 34949ead1f1f290710441d40187f7a35534ec1b2 Mon Sep 17 00:00:00 2001
From: David Robertson <davidr@element.io>
Date: Thu, 21 Jul 2022 13:23:05 +0100
Subject: [PATCH] Track DB txn times w/ two counters, not histogram (#13342)

---
 changelog.d/13342.misc      | 1 +
 synapse/storage/database.py | 8 +++++---
 2 files changed, 6 insertions(+), 3 deletions(-)
 create mode 100644 changelog.d/13342.misc

diff --git a/changelog.d/13342.misc b/changelog.d/13342.misc
new file mode 100644
index 000000000000..ce9c816b9c1a
--- /dev/null
+++ b/changelog.d/13342.misc
@@ -0,0 +1 @@
+When reporting metrics is enabled, use ~8x less data to describe DB transaction metrics.
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index ea672ff89e73..b394a6658b09 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -39,7 +39,7 @@
 )
 
 import attr
-from prometheus_client import Histogram
+from prometheus_client import Counter, Histogram
 from typing_extensions import Concatenate, Literal, ParamSpec
 
 from twisted.enterprise import adbapi
@@ -76,7 +76,8 @@
 sql_scheduling_timer = Histogram("synapse_storage_schedule_time", "sec")
 
 sql_query_timer = Histogram("synapse_storage_query_time", "sec", ["verb"])
-sql_txn_timer = Histogram("synapse_storage_transaction_time", "sec", ["desc"])
+sql_txn_count = Counter("synapse_storage_transaction_time_count", "sec", ["desc"])
+sql_txn_duration = Counter("synapse_storage_transaction_time_sum", "sec", ["desc"])
 
 
 # Unique indexes which have been added in background updates. Maps from table name
@@ -795,7 +796,8 @@ def new_transaction(
 
             self._current_txn_total_time += duration
             self._txn_perf_counters.update(desc, duration)
-            sql_txn_timer.labels(desc).observe(duration)
+            sql_txn_count.labels(desc).inc(1)
+            sql_txn_duration.labels(desc).inc(duration)
 
     async def runInteraction(
         self,