Track db txn time in millisecs

... to reduce the amount of floating-point foo we do.

1 files changed, 5 insertions, 3 deletions

diff --git a/synapse/util/metrics.py b/synapse/util/metrics.py

index 8d22ff3068..d25629cc50 100644
--- a/synapse/util/metrics.py
+++ b/synapse/util/metrics.py
@@ -72,6 +72,7 @@ block_db_txn_count = metrics.register_counter(
     ),
 )
 
+# seconds spent waiting for db txns, excluding scheduling time, in this block
 block_db_txn_duration = metrics.register_counter(
     "block_db_txn_duration_seconds", labels=["block_name"],
     alternative_names=(
@@ -95,7 +96,7 @@ def measure_func(name):
 class Measure(object):
     __slots__ = [
         "clock", "name", "start_context", "start", "new_context", "ru_utime",
-        "ru_stime", "db_txn_count", "db_txn_duration", "created_context"
+        "ru_stime", "db_txn_count", "db_txn_duration_ms", "created_context"
     ]
 
     def __init__(self, clock, name):
@@ -115,7 +116,7 @@ class Measure(object):
 
         self.ru_utime, self.ru_stime = self.start_context.get_resource_usage()
         self.db_txn_count = self.start_context.db_txn_count
-        self.db_txn_duration = self.start_context.db_txn_duration
+        self.db_txn_duration_ms = self.start_context.db_txn_duration_ms
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         if isinstance(exc_type, Exception) or not self.start_context:
@@ -145,7 +146,8 @@ class Measure(object):
             context.db_txn_count - self.db_txn_count, self.name
         )
         block_db_txn_duration.inc_by(
-            context.db_txn_duration - self.db_txn_duration, self.name
+            (context.db_txn_duration_ms - self.db_txn_duration_ms) / 1000.,
+            self.name
         )
 
         if self.created_context: