Can we limit the number of active jobs on a given printer?

[Helge Blischke]

Kai Lanz wrote:

> 
> The other day I was surprised to see more than one active job being sent
> to one of our plotters. The output of lpq for that plotter showed 7 jobs
> with rank "active", and there were 7 backend processes running
> simultaneously. Is that normal for CUPS? I had always thought there would
> only ever be one active job on any given printer. It didn't cause a
> problem with printing, but we have custom-written plotter control and
> accounting software that implicitly assumes there can be at most one
> active job (one running backend). It would help us if we could configure
> CUPS (or write a backend) so it would send jobs to a printer strictly one
> at a time. Is there a way to do that?
> 
> MaxJobsPerPrinter doesn't do what we want; it limits the number of jobs
> that can be spooled, not the number that can be active. And waitjob
> appears to be an option for the IPP backend only.
> 
> This is RHEL 4 on Intel x86_64 with CUPS 1.1.22. The plotters are HP 800ps
> and T1120ps DesignJets. The backend is a simple bash script that sends
> data to the plotter through a pipeline of filters after confirming that
> the job to be printed has been properly released by a valid user; it then
> marks the job as "printed" in a log file.
> 
> --
> Kai Lanz           Stanford University        School of Earth Sciences

As you backend is a shell scrip, please post (an URL to) it. When looking 
into it, perhaps a (partly) solution might come to my mind ...

Helge