"intelligent" load balancing or duplex detection

[Helge Blischke]

Elvin Lee wrote:
> 
> Robert E A Harvey wrote:
> > Elvin Lee wrote:
> >
> >> The problem, of course, is that only one of the printers support
> >> duplexing. Is there a way that I can configure cups on the server to
> >> automatically send duplex jobs to one of the printers in the class,
> >> rather than choosing between the two?
> >
> >
> > I've read the official reply, but it's got me thinking.  Are these
> > network connected? they sound like it, being an 'N' product.
> >
> > It might be possible to create a totally separate duplex queue, pointing
> > separately  to the duplex machine, and print to that?  It would
> > certainly work with jetadmin on Solaris, I've done that sort of thing -
> > an A4 queue and an A5 queue onto the same machine.
> >
> > Never tried it with CUPS - my system was quite straightforward, two
> > printers each with a unique queue, 'cos they were not physically close.
> 
> Yes, they are networked, and it is possible to have a duplex queue and a
> non-duplex queue. However, I would like to ideally have the feature I
> described previously because users will inevitably try printing duplex
> jobs to the non-duplex queue (or vice versa) and then we're back to
> square one.
> 
> Of course, the alternative would be to hack the PPD files to disable the
> ability to print duplex jobs to the printers in the non-duplex queue...
> Thus if they wanted to print duplex, they would have to select the other
> queue. This is a potential workaround, but not really a substitute -- I
> feel it lacks the functionality and robustness of the solution I
> suggested. But I may have to set up something of this sort as Fall
> quarter is rapidly approaching...
> 
> Thanks for taking the time to write. All help is appreciated. :)
> 
A workaround I've used several times for similar issues is to write a
special
(scripted) backend that checks the job for duplex printing and then
forwards the
job to the correct physical printer.
If you are sure that duplex printing is only selected by job attributes,
it is quite
easy to check the option string on the command line, otherwilse you'd
have to feed
the job through Ghostscript (the nulldevice for speed) and intercept the
setpagedevice
operator and the level1 compatible things (like duplexmode etc; see the
PPD).

Helge


-- 
H.Blischke at srz-berlin.de
H.Blischke at srz-berlin.com
H.Blischke at acm.org