Load balancing and Implicit Classes

John E. Vincent cups-bugs at lusis.org
Sat Jun 19 09:13:44 PDT 2004


I have a question regarding how cups handles loadbalancing and implicit classes.

Let me run down the scenario:

We have two cups servers currently. Right now these have two printers loaded. We will soon be at over 1000 printers once we are done with the pilot program, hence the need for loadbalancing.

Browsing is enabled and so are implicit classes. I've created the two printers on each cups server.

Initially we simply added each CUPS server to our load balancer and started testing. We ended up with CUPS disabling both print queues because they were conflicting for access to the printer itself. I've posted notes previously regarding our current printer setup (HP LJ1300 connected to Links WPS11 Print servers in our retail locations). These devices have a broken IPP implementation so LPD was our only option.

What I ended up doing was changing one of the cups servers on our load balancer to a hot-spare. I assumed I would let cups handle the load balancing internally. After all, each server has matching printers. According to the docs it should alternate between the two.

This wasn't happening and it seems that it is because the primary cups server is always using the local printer because it is behaving as a CUPS client.

I enabled ImplicitAnyClasses and now things are unmanageable with just two printers! I've got three CUPS entries per printer - the implicitany printer, the locally defined printer and printer at server2. When I get to 1000 printers, we won't be able to manage this at all.

We currently print to the CUPS servers using the Java API with the following URI - http://virtualprintserver:631/printers/printername.

Would we get the load balancing behaviour we need if we printed to http://virtualprintserver:631/classes/printername or will we need to use http://virtualprintserver:631/classes/Anyprintername?

Any help would be appreciated. I'm at a bit of a loss as to how we should procede.

Thanks,

John E. Vincent




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