CentOS - Jan 2009 - Cron daemon with better precision?

Greetings list-

I'm on the hunt for a cron scheduler that supports definitions to the
second. Obviously, every cron daemon supports minute/hour/etc but I have a
special application that requires finer granularity.

I know I know... someone will say "The load will be horrendous on your
system" or "Why don't you simply schedule your cron every minute
and make up the higher precision in your application?". Unfortunately, this
will not work. I really need a cron daemon that can schedule to the second.

All ideas/thoughts/suggestions/etc welcome. Thank you!

Tim Nelson
Systems/Network Support
Rockbochs Inc.
(218)727-4332 x105

> Greetings list-
>
> I'm on the hunt for a cron scheduler that supports definitions to the
> second. Obviously, every cron daemon supports minute/hour/etc but I have a
> special application that requires finer granularity.
>
> I know I know... someone will say "The load will be horrendous on your
> system" or "Why don't you simply schedule your cron every
minute and make
> up the higher precision in your application?". Unfortunately, this
will
> not work. I really need a cron daemon that can schedule to the second.
>
> All ideas/thoughts/suggestions/etc welcome. Thank you!
>
> Tim Nelson
> Systems/Network Support
> Rockbochs Inc.
> (218)727-4332 x105
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
Does the task really have to run every second or can it get kicked off and
run 60 times within the minute?

Andrew

On Fri, 2009-01-16 at 13:46 -0600, Tim Nelson wrote:
> Greetings list-
> 
> I'm on the hunt for a cron scheduler that supports definitions to the
second. Obviously, every cron daemon supports minute/hour/etc but I have a
special application that requires finer granularity.
> 
> I know I know... someone will say "The load will be horrendous on your
system" or "Why don't you simply schedule your cron every minute
and make up the higher precision in your application?". Unfortunately, this
will not work. I really need a cron daemon that can schedule to the second.
> 
> All ideas/thoughts/suggestions/etc welcome. Thank you!
If the other suggestion doesn't meet your needs, consider the following.

Even a cron scheduler with 1 second resolution _may_ not give you what
you need. This is because initializations may cause the application to
start running too late. This possibility seems probable based on the
need for 1 second resolution.

Of course, you could set the cron to kick off some average number of
seconds earlier, but variability of system load, cache contents, disk
I/O status, etc. could cause it to start sooner or later on any given
invocation.

IMO, any application designed to need 1 second resolution (if that is
the case here) should run as a daemon and handle the timing needs itself
or accept signals (such as SIGUSR1 or whatever) from an external
"supervisor" that tells the daemon "do it now". That way
everything is
already in memory (presuming swap is disallowed) and only system
controlled resources, such as cache, buffers and disk I/O status could
cause high variability. Those issues can be handled by ensuring load
versus capacity is adequate during critical times. Of course, that might
also then allow a cron-like dispatching process to be adequate for the
task. It just depends on the host configuration for resources and load.
> 
> Tim Nelson
> <snip sig stuff>
If this is for a process control application with tight timing
constraints, I suggest a system dedicated to the task. Long ago and far
away, I designed and implemented a custom hardware and software system
to capture many items of data from a large number of textile looms. This
was before such was available "off the shelf". It ran on a true UNIX
system on 486DX/2 and 586 hardware. From that background I can strongly
suggest dedicated hardware if your application is similar.

-- 
Bill

Tim Nelson wrote:
> Greetings list-
>
> I'm on the hunt for a cron scheduler that supports definitions to the
> second. Obviously, every cron daemon supports minute/hour/etc but I have a
> special application that requires finer granularity.
Try this ?

http://vexus.ca/products/avatar/v4/

My company uses an older version of this:
http://www.tidalsoftware.com/Default.aspx

Though we are moving away from it, to cron and Sun Grid Engine.

nate

> I'm on the hunt for a cron scheduler that supports definitions to the
second.
> Obviously, every cron daemon supports minute/hour/etc but I have a special 
> application that requires finer granularity.
> 
> I know I know... someone will say "The load will be horrendous on your
system"
> or "Why don't you simply schedule your cron every minute and make
up the higher
> precision in your application?". Unfortunately, this will not work. I
really
> need a cron daemon that can schedule to the second.
Why wouldn't a wrapper script run at the minute and sleeping xx seconds
before running the application work out?

JD

Tim Nelson napsal(a):
> Greetings list-
> 
> I'm on the hunt for a cron scheduler that supports definitions to the
second. Obviously, every cron daemon supports minute/hour/etc but I have a
special application that requires finer granularity.
> 
> I know I know... someone will say "The load will be horrendous on your
system" or "Why don't you simply schedule your cron every minute
and make up the higher precision in your application?". Unfortunately, this
will not work. I really need a cron daemon that can schedule to the second.
> 
> All ideas/thoughts/suggestions/etc welcome. Thank you!
Hi,
look at http://www.gnu.org/software/mcron/
David Hrb??