Track db txn time in millisecs

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

2 files changed, 11 insertions, 6 deletions

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

index ca71a1fc27..a78e53812f 100644
--- a/synapse/util/logcontext.py
+++ b/synapse/util/logcontext.py
@@ -59,7 +59,7 @@ class LoggingContext(object):
 
     __slots__ = [
         "previous_context", "name", "ru_stime", "ru_utime",
-        "db_txn_count", "db_txn_duration", "usage_start", "usage_end",
+        "db_txn_count", "db_txn_duration_ms", "usage_start", "usage_end",
         "main_thread", "alive",
         "request", "tag",
     ]
@@ -97,7 +97,10 @@ class LoggingContext(object):
         self.ru_stime = 0.
         self.ru_utime = 0.
         self.db_txn_count = 0
-        self.db_txn_duration = 0.
+
+        # ms spent waiting for db txns, excluding scheduling time
+        self.db_txn_duration_ms = 0
+
         self.usage_start = None
         self.usage_end = None
         self.main_thread = threading.current_thread()
@@ -205,7 +208,7 @@ class LoggingContext(object):
 
     def add_database_transaction(self, duration_ms):
         self.db_txn_count += 1
-        self.db_txn_duration += duration_ms / 1000.
+        self.db_txn_duration_ms += duration_ms
 
 
 class LoggingContextFilter(logging.Filter):
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: