Sorry, fork is not the correct OS term, as the new process is not a copy of the parent process. The new process is just that, a new process.
John Heenan On Jan 7, 11:14 am, John Heenan <[email protected]> wrote: > My logs indicate that a web2py soft cron command to execute a Python > file at or after a given interval is achieved by forking off another > Python instance, instead of doing an exec on the contents of the file. > A sample from my standard output logs is below. > > This is confirmed from examining web2py/gluon/contrib/cron.py I see > that a Python Popen is executed. This forks off another process, > connects standard input, output and error and then waits. > > This is overkill if the only task of a crontab is to expire sessions > using Python code and there is a goal to minimise memory hungry > processes occupying memory, no matter for how short, that might risk > bringing the swap file into use. > > Massimo's way of expiring sessions from the model file is less > resource intensive, if Python code is used. > > John Heenan > > 2010-01-06 15:15:13,876 - INFO - WEB2PY CRON (soft): Application: zgus > executing **applications/admin/cron/expire_sessions.py in /home/zgus/ > web2py/web2py at 2010-01-06 15:15:13.876653 > 2010-01-06 15:15:14,636 - INFO - WEB2PY CRON Call returned: default > applications appear to be installed already > web2py Enterprise Web Framework > Created by Massimo Di Pierro, Copyright 2007-2009 > Version 1.67.2 (2009-09-28 16:29:33) > Database drivers available: SQLite3 > WARNING:root:GUI not available because Tk library is not installed > > On Jan 6, 2:19 pm, mdipierro <[email protected]> wrote: > > > I guess the book needs some cleanup in this respect. > > > I normally expire sessions in the model iteself. No cron and no > > process. > > > On Jan 5, 10:08 pm, John Heenan <[email protected]> wrote: > > > > I am a bit of a loss though as to why page 121 provides the following > > > web2py specific web2py/applications/xxx/cron/crontab entry example for > > > expiring sessions: > > > > @hourly root *applications/admin/cron/expire_sessions.py > > > > AND why page 123 provides an example of how to run web2py crontabs > > > from /etc/crontab (called 'hard cron' by web2py): > > > > 0-59/1 * * * * web2py cd /var/www/web2py/ && python web2py.py -C -D 1 > > > > >> /tmp/cron.output 2>&1 > > > > YET page 302 in the the deployment recipes section appears to prefer > > > keeping a python process lying around in memory to expire sessions > > > that is only used relatively infrequently. > > > > I imagine most of us on this list are severely constrained with regard > > > to resources for live deployment of web2py. I use a 256MB VPS and make > > > sure I only run the absolute minimum number of processes. Some on this > > > list will have even even less memory available (such as if using > > > webfaction). > > > > I have only one process running that goes above 3MB memory use: a > > > single persistent python process that runs all my web2py apps and uses > > > 37MB of memory . The webserver (lighttpd) occupies 2.3MB and does not > > > fork. These memory sizes occupy RAM and swapped memory if not enough > > > RAM memory is available. The potential memory use of python is 236MB > > > (VSZ size). > > > > Under these circumstances the web2py labelled 'soft cron' option is > > > attractive as no extra processes are spawned: the python process that > > > runs web2py runs web2py specific crontabs in web2py/applications/xxx/ > > > cron/crontab. > > > > John Heenan > > > > On Jan 6, 2:11 am, mdipierro <[email protected]> wrote: > > > > > thanks > > > > > On Jan 5, 9:48 am, John Heenan <[email protected]> wrote: > > > > > > On Jan 6, 1:40 am, John Heenan <[email protected]> wrote: > > > > > > > Here is a hint for using the book listed command > > > > > > nohup python web2py.py -S yourapp -R scripts/sessions2trash.py & > > > > > > in /etc/rc.local, to enable automatic start of this script on boot. > > > > > > This hint is of course only relevant if you don't already use /etc/ > > > > > rc.local to start up web2py. I use a scrpt in /etc/init.d instead to > > > > > start up web2py. > > > > > > John Heenan
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