Scheduling of tasks/what's the maximum frequency of the task being executed?

[Ed Wilts]

On Thu, May 13, 2004 at 09:23:48AM -0400, Sebastijan Petrovic wrote:
> I have several tasks that need to be executed every two seconds.  Using
> RH9 builtin task scheduler the greatest frequency of a task is every 5
> minutes.  At command also does not allow for such frequent schedule.
> 
>  
> 
> Do any of you know of a way to accomplish this.  Details of what I need
> done are as follows:
> 
> 1.	Run WGET to download an image (that changes every two seconds)
> using http, keep over-writing that image and 
> 2.	Upload that image every two seconds to an FTP share 

Against my better judgement, since I have some doubts that you really
want to do this, here's how I would tackle this:

1.  Do not use any scheduler whatsoever.
2.  I'm assuming the FTP server is yours.  Trying to log into somebody
else's FTP server every 2 seconds goes beyond rude - it's offensive.
3.  Write a perl script to do the get & put.  Don't use wget but use the
callable routines to get the file.  Open a single FTP session and put
the file regularly.  Better yet would be to write a custom app to copy
the file over, or even better would be to not copy the file over unless
it's needed - either via nfs, smb, or something.  Copying the same image
every 2 seconds is a large waste of resources unless users are actually
pulling that image off your FTP server every 2 seconds.  
4.  Do *NOT* try to log into the FTP server every 2 seconds to put a
file.  FTP isn't that efficient and doing a new login every 2 seconds is
going to kill the FTP server.  

-- 
Ed Wilts, Mounds View, MN, USA
mailto:ewilts at ewilts.org
Member #1, Red Hat Community Ambassador Program