Add StatsReporter timer helper; use it to report time spent in Tracke…

…dTask execution

Summary: It is useful to track how long tasks take.

Test Plan: Unit, still queued.

Reviewers: jukka

Reviewed By: jukka

Subscribers: changesbot, wwu

Differential Revision: https://tails.corp.dropbox.com/D97157

changes/ext/statsreporter.py

@@ -1,6 +1,8 @@
 import statsd
 import re
+import time
 import logging
+from contextlib import contextmanager
 
 logger = logging.getLogger('statsreporter')
 
@@ -93,6 +95,16 @@ def log_timing(self, key, duration_ms):
         if self._client:
             self._client.timing(key, duration_ms)
 
+    @contextmanager
+    def timer(self, key):
+        """A contextmanager that reports the duration in milliseconds on exit."""
+        t0 = time.time()
+        try:
+            yield
+        finally:
+            duration_ms = int(1000 * (time.time() - t0))
+            self.log_timing(key, duration_ms)
+
     _KEY_RE = re.compile(r'^[A-Za-z0-9_-]+$')
 
     @classmethod

changes/queue/task.py

@@ -73,8 +73,9 @@ def __init__(self, func, max_retries=MAX_RETRIES, on_abort=None):
         self.__code__ = getattr(func, '__code__', None)
 
     def __call__(self, **kwargs):
-        with self.lock:
-            self._run(kwargs)
+        with statsreporter.stats().timer('task_duration_' + self.task_name):
+            with self.lock:
+                self._run(kwargs)
 
     def __repr__(self):
         return '<%s: task_name=%s>' % (type(self), self.task_name)