Merge pull request #1186 from tahoe-lafs/3883.drop-cpuusagemonitor-foolscap-dep

Drop the Foolscap dependency in allmydata.stats

Fixes: ticket:3883

src/allmydata/stats.py

@@ -1,54 +1,39 @@
 """
 Ported to Python 3.
 """
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
-from future.utils import PY2
-if PY2:
-    from future.builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, list, object, range, str, max, min  # noqa: F401
-    from time import clock as process_time
-else:
-    from time import process_time
+from collections import deque
+from time import process_time
 import time
+from typing import Deque, Tuple
 
 from twisted.application import service
 from twisted.application.internet import TimerService
 from zope.interface import implementer
-from foolscap.api import eventually
 
 from allmydata.util import log, dictutil
 from allmydata.interfaces import IStatsProducer
 
 @implementer(IStatsProducer)
 class CPUUsageMonitor(service.MultiService):
-    HISTORY_LENGTH = 15
-    POLL_INTERVAL = 60  # type: float
+    HISTORY_LENGTH: int = 15
+    POLL_INTERVAL: float = 60
+    initial_cpu: float = 0.0
 
     def __init__(self):
         service.MultiService.__init__(self)
-        # we don't use process_time() here, because the constructor is run by
-        # the twistd parent process (as it loads the .tac file), whereas the
-        # rest of the program will be run by the child process, after twistd
-        # forks. Instead, set self.initial_cpu as soon as the reactor starts
-        # up.
-        self.initial_cpu = 0.0 # just in case
-        eventually(self._set_initial_cpu)
-        self.samples = []
+        self.samples: Deque[Tuple[float, float]] = deque([], self.HISTORY_LENGTH + 1)
         # we provide 1min, 5min, and 15min moving averages
         TimerService(self.POLL_INTERVAL, self.check).setServiceParent(self)
 
-    def _set_initial_cpu(self):
+    def startService(self):
         self.initial_cpu = process_time()
+        return super().startService()
 
     def check(self):
         now_wall = time.time()
         now_cpu = process_time()
         self.samples.append( (now_wall, now_cpu) )
-        while len(self.samples) > self.HISTORY_LENGTH+1:
-            self.samples.pop(0)
 
     def _average_N_minutes(self, size):
         if len(self.samples) < size+1:

src/allmydata/test/test_stats.py

@@ -17,7 +17,7 @@ from allmydata.util import pollmixin
 import allmydata.test.common_util as testutil
 
 class FasterMonitor(CPUUsageMonitor):
-    POLL_INTERVAL = 0.1
+    POLL_INTERVAL = 0.01
 
 
 class CPUUsage(unittest.TestCase, pollmixin.PollMixin, testutil.StallMixin):
@@ -36,9 +36,9 @@ class CPUUsage(unittest.TestCase, pollmixin.PollMixin, testutil.StallMixin):
         def _poller():
             return bool(len(m.samples) == m.HISTORY_LENGTH+1)
         d = self.poll(_poller)
-        # pause one more second, to make sure that the history-trimming code
-        # is exercised
-        d.addCallback(self.stall, 1.0)
+        # pause a couple more intervals, to make sure that the history-trimming
+        # code is exercised
+        d.addCallback(self.stall, FasterMonitor.POLL_INTERVAL * 2)
         def _check(res):
             s = m.get_stats()
             self.failUnless("cpu_monitor.1min_avg" in s)