>> I was worried by potential caching issues with the database that >> may prevent my cron script to retrieve the latest boolean value.
It sounds as if you're worried about a race condition when scale up -- e.g. let's say you need to run a lot of background processes and decide to split them up among several machines, each with their own cron jobs. If Machine A's cron job and Machine B's cron job both check the database at the same time, they'll both see that the process isn't running and start it up -- resulting in two copies of the process instead of just one. Am I correct in saying that's what you're concerned about? If so, a simple solution would be to just wrap that part of the code in a transaction. This will ensure Machine B doesn't get a response back from the database until Machine A finishes updating it. Aside from that, this seems fine. -- Andrew On Jul 21, 9:10 am, Philippe Josse <phildev7...@gmail.com> wrote: > Hi there, > > I would like to have your feedback on the way I am running daemon scripts > for my Django/ Python app. I know this is definitely not the "one best way", > but this is a solution I came up with that seemed simple to implement. (I am > a real newbie!) > > My constraints: > - getting a few processs constantly repeating themselves > - getting an email notification if one of the process crashes > > I set up a cron job that is launching a "daemon manager" script every > minute. This script is querying a PostGreSQL database to retrieve boolean > values associated to the state of my background processes (running / not > running). If the database indicates the process is not running, then the > cron script launches it. > > Boolean values are updated by each process when it starts and finishes. > Currently, it seems to work fine - but my background processes are very > quick to execute. When my user base will grow, they may last longer and it > will be essential that background processes do not run concurrently. > > Would that solution work? I was worried by potential caching issues with the > database that may prevent my cron script to retrieve the latest boolean > value. Is there any real risk? > > Thanks for your feedback! --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
