Sorry, didn't notice the list changed. On Fri, Jun 13, 2014 at 8:40 AM, Michael Still <mi...@stillhq.com> wrote: > On Thu, Jun 12, 2014 at 10:05 PM, Tom Cammann <tom.camm...@hp.com> wrote: >> Hello, >> >> I'm addressing https://bugs.launchpad.net/oslo/+bug/1326020 which is >> dealing with periodic tasks. >> >> There is currently a code block that checks if a task is 0.2 seconds >> away from being run and if so it run now instead. Essentially >> coalescing nearby tasks together. >> >> From oslo-incubator/openstack/common/periodic_task.py:162 >> >> # If a periodic task is _nearly_ due, then we'll run it early >> idle_for = min(idle_for, spacing) >> if last_run is not None: >> delta = last_run + spacing - time.time() >> if delta > 0.2: >> idle_for = min(idle_for, delta) >> continue >> >> However the resolution in the config for various periodic tasks is by >> the second, and I have been unable to find a task that has a >> millisecond resolution. I intend to get rid of this coalescing in this >> bug fix. >> >> It fits in with this bug fix as I intend to make the tasks run on their >> specific spacing boundaries, i.e. if spacing is 10 seconds, it will run >> at 17:30:10, 17:30:20, etc. >> >> Is there any reason to keep the coalescing of tasks? > > The resolution for periodic tasks is seconds, but a task can take a > non-integer number of seconds to have run. This code was added (IIRC, > it was a long time ago) in an attempt to detect tasks that were about > to run and kick them off straight away instead of doing very small > sleeps. I think that's probably bogus, and I'm ok with you removing > it. > > The historical context here is that periodic tasks used to have very > unpredictable frequencies, you'd specify the number of periodic task > loop "ticks" you wanted as a frequency, but that wasn't a predictable > time because sometimes the periodic task loop was busier than others. > Additionally, the spacing didn't take into account how long the jobs > took to run, so if you specified 10 ticks, that was a 10 tick wait > between runs, even if the last run took an hour. So... I think I was a > little focused on timing when I wrote this code, and probably went too > far in the other direction. > > Cheers, > Michael > > -- > Rackspace Australia
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