commit 02760c0638ee57b456920beccba178669a378537 Merge: d138f557 7d639f21 Author: Damian Johnson atagar@torproject.org Date: Thu Sep 21 10:23:36 2017 -0700

Close control socket faster when under load

When receiving a high volume of traffic (such as DEBUG events on a busy relay) our controller can take seconds or even minutes to close. This is because we send a QUIT signal, then wait for the response which is stuck behind potentially thousands of events.

From what I can tell there's little point in issuing a QUIT so dropping that, and setting a time limit for processing backlogged events.

I've done what I can to lighten our socket's recv() method, and even without the timeout we now process events much faster. But on busy relays under DEBUG load we simply cannot keep up. Clearly an edge case though, hence this compromise. The timeout is high enough that users will effectively never hit it, but when the controller connection is saturated we still work.

Tested via the following script on my relay...

import os import time

import stem.control import stem.util.proc import stem.util.str_tools

start_time = time.time() samplings = [] last_sample = None

with stem.control.Controller.from_port() as controller: controller.authenticate() controller.add_event_listener(lambda *args: None, 'DEBUG')

while True: utime, stime = stem.util.proc.stats(os.getpid(), stem.util.proc.Stat.CPU_UTIME, stem.util.proc.Stat.CPU_STIME) total_cpu_time = float(utime) + float(stime)

if last_sample: samplings.append(total_cpu_time - last_sample) print '%0.1f%% (%s)' % (sum(samplings) / len(samplings) * 100, stem.util.str_tools.time_label(time.time() - start_time))

last_sample = total_cpu_time time.sleep(1)

docs/change_log.rst | 4 +- stem/control.py | 29 +++++---- stem/response/__init__.py | 2 +- stem/socket.py | 115 +++++++++++++++++----------------- stem/util/log.py | 19 ++++++ stem/util/system.py | 18 +++--- test/settings.cfg | 1 + test/unit/response/control_message.py | 15 ++--- test/unit/util/__init__.py | 1 + test/unit/util/log.py | 23 +++++++ 10 files changed, 141 insertions(+), 86 deletions(-)