Active waiting?

[Nicolas Sebrecht]

On Mon, Mar 23, 2015 at 05:00:41PM +0100, Sebastian Spaeth wrote:
> Am 23.03.2015 um 15:53 schrieb Nicolas Sebrecht:
> > On Mon, Mar 23, 2015 at 01:01:12PM +0100, Alvaro Gamez wrote:
> >>    What a pity :(
> >>    If there's anything I can research on this to improve offlineimap
> >>    please let me know in which direction.
> > 
> > This is a known issue but nobody looked into this deeply.
> > 
> >   https://github.com/OfflineIMAP/offlineimap/issues/81
> > 
> > We need to know which Python code is to blame, whether it's in a library
> > or in our code. With more information we will clearly see if we can do
> > something or not.
> 
> Actually, yes, I did look into this previously :-). I added a comment to
> issue 81 to provide a tad more detail. My research is from a few years
> back and I am writing from memory.

Sorry, I can't recall about this. Thanks for the input.

> Thing is, that our main thread needs to wait for it's daughter threads
> to exit. This is in threadutils.py:exitnotifymonitorloop.
> 
> We use a Queue in which all exiting threads are put() and loop around,
> waiting with .get(60) for one of those threads to finish.
> Queue().get(60) will wakeup every 50ms or so to see if the condition has
> been fulfilled. If you do not specify a timeout, there will be no
> wakeups, but the main thread will also not listen (and react) to
> signals, such as sent by CTRL-C (or SIGTERM). So we would run danger of
> hanging indefinitely and not be able to react on Ctrl-C.
> 
> So if you find a solution that lets us wait for daughter threads and
> reacts to Ctrl-C (and other signals), we are gold. Unfortunately, I
> failed to find such a solution. (by, this is related to
> http://bugs.python.org/issue1360).
> 
> The good news is that the signal issue seems to have been solved in
> python3 (according to the upstream bug report), so we are using python3,
> we should be able to use that code without any timeout, and save lots of
> wakeups. (untested).

Good to know.

Can't we do something like that?

--- >8 ---
Subject: [PATCH] WIP: avoid Queue.get() too much to avoid battery sucking
From: Nicolas Sebrecht <nicolas.s-dev at laposte.net>

TODO: add new configuration option.
---

 offlineimap/threadutil.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/offlineimap/threadutil.py b/offlineimap/threadutil.py
index f69f8a6..edc57fb 100644
--- a/offlineimap/threadutil.py
+++ b/offlineimap/threadutil.py
@@ -23,6 +23,8 @@ except ImportError: # python3
 import traceback
 import os.path
 import sys
+import time
+
 from offlineimap.ui import getglobalui
 
 ######################################################################
@@ -112,6 +114,7 @@ def exitnotifymonitorloop(callback):
             thrd = exitthreads.get(True, 60)
             # request to abort when callback returns true
             do_loop = (callback(thrd) != True)
+            time.sleep(2)
         except Empty:
             pass
 
-- 
Nicolas Sebrecht