Because they os timestamp only can only tell you when a task has started (or stopped, depending on when it was created) it does not contain enough information to give you a time range (time and stop). Cron needs to know when the previous crondance started and whether is was completed or not. The original implementation was doing the check using locks and that resulted in a large number of try... except... The current implementation removes most of the try.. except... (people complained about that) and just stores start_time, stop_time explicitly in a picke.
On Apr 12, 8:00 am, AchipA <attila.cs...@gmail.com> wrote: > To correct myself, it seems the cron in web2py no longer uses the > filesystem timestamps, but cPickles timestamps from/to the lock file. > I'm not sure why Massimo changed it, but this *is* a bigger overhead > than it was previously (as it needs to do file locking and > cPickle.load() on every single request - as opposed to a simple cached > non-locking filesystem call). > > On Apr 1, 8:20 pm, AchipA <attila.cs...@gmail.com> wrote: > > > Exactly, hardcron checks once a minute, softcron checks on each page > > load. The 'check' is calling a function or two and comparing a file's > > timestamp, so not *that* much more expensive. > > > On Apr 1, 7:51 pm, Jonathan Lundell <jlund...@pobox.com> wrote: > > > > On Apr 1, 2010, at 10:37 AM, AchipA wrote: > > > > > There is some overhead, but efficiency is a disputable term - there is > > > > certainly more overhead than hardcron, but IMO not in a way that would > > > > affect overall performance unless you're running it on a site that has > > > > hundreds of thousands of hits per day... > > > > Perhaps we could change (or eliminate) the wording. How about simply > > > 'Using softcron'? > > > > I'm curious: what is the extra overhead of soft vs hardcron? Just that it > > > does a test on each page access? I'm guessing that's pretty cheap. > > > > > On Apr 1, 5:40 pm, Jonathan Lundell <jlund...@pobox.com> wrote: > > > >> Section 4.17 (cron) mentions hard vs softcrondefaults, but doesn't say > > > >> how to override them. > > > > >> Section 4.1 (cli) doesn't list --softcron > > > > >> The startup message for softcronsays: 'Using softcron (but this is not > > > >> very efficient)' > > > > >> In what sense "not efficient"? I understand that the timing is less > > > >> consistent, but is there really more overhead? softcron seems like a > > > >> pretty reasonable choice if all you're doing it deleting expired > > > >> sessions. -- To unsubscribe, reply using "remove me" as the subject.
