Detect Printer failure & high CPU usage

[Elly K]

Thanks Johannes.  You have given us plenty to think/read about.  We also have official support for this product and we will explore that route as well.

Thanks again!

>
> Hello,
>
> On Oct 10 12:13 Elly K wrote (shortened):
> > I got CUPS 1.4.4 running on a virtual (SLES 10.3) Linux server
> > on an IBM Mainframe. I use this server to print PDF's
> > from my java application.  And I have a few questions
>
> If you have whatever official support contract, I recommend
> to use it to get official support for what you have set up.
> Any help via cups at easysw.com is only informal and voluntary
> and neither official support nor is there any kind of warranty.
>
>
> > 1) From the CUPS JOBS web page, I can see information
> > on some printers about "Broken Pipe" and then there are
> > messages about "foomatic failed" etc.,  What I tried to do
> > in my Java application was to use the Runtime..exec() methods
> > to read this JOBS web page and generate emails if I find
> > strings matching "Broken pipe" or "failed" - Turned out to be
> > a bad idea.  Most of the time, the web page is read in time,
> > but sometimes it takes a long time and it creates a serious backlog.
> > Is there a more reliable way to detect printer problem situations
> > from my java application?
>
> I don't know about Java but you may use CUPS "subscriptions"
> which let the cupsd send emails in case of particular events, see
> http://www.cups.org/documentation.php/doc-1.4/ref-subscriptions-conf.html
>
>
> > 2) When I print my PDF's I see a process called gs executing and
> > sometimes there are multiple instances of gs running based
> > on print requests.  My question is the CUPS server always seems
> > to be using a lot of CPU when it's being used.  When not in use,
> > the CPU use is almost nothing.  But when it is being hit even
> > for a couple of pages, the usage briefly spikes to 99% before
> > retreating.  And when there's heavy load, the CPU is pegged
> > at 99% for a while.  Is this normal?
>
> This is normal - it is even better than normal. It would be a
> bug in the CPU scheduler in the Linux kernel if it would try
> to avoid that the CPU is actually used when it is actually
> needed. Ghostscript may need very much CPU to render
> the PostScript of the document which is to be printed
> depending on the actual PostScript of the document.
> If you are interested in some special PostScript examples
> you may search in Google e.g. for "PostScript raytracer".
>
>
> > 3) I would like to have another CUPS server to act as a backup
> > to the main server.  In case, the main server is down or under
> > heavy stress, I would like this backup server to take some
> > of the load. I'm sure there's plenty of software out there
> > to do this sort of thing, but any ideas on how to do this
> > the best way?
>
> At the moment I don't know about a comprehensive documentation
> which provides background information and describes details
> about "load balancing and fail-safe printing functionality"
> except the snippet in
> http://www.cups.org/documentation.php/doc-1.4/spec-browsing.html
> ------------------------------------------------------------------
> A key feature of CUPS printer sharing is support for implicit
> classes, which are automatically-created classes for printers
> that are shared by multiple servers. These implicit classes
> provide automatic load balancing and fail-safe printing
> functionality transparently to the user.
> ------------------------------------------------------------------
>
> This means:
> Run two servers simultaneously and use the default CUPS browsing
> (i.e. let both servers announce their queues simultaneously and
> let the client systems accept the announced queues from both servers)
> so that CUPS' default "implicit classes" results load balancing
> on the server and fail-safe printing functionality on the clients
> automatically.
>
> There could be problems if the same network printers are used
> by both servers simultaneously (i.e. when both servers try to send
> printing data to one same network printer simultaneously), see
> http://en.opensuse.org/SDB:Printing_via_TCP/IP_network
> In this case you would have to split those network printers
> which cause such problems into two sets to that the network
> printers in one set belong only to one server and the network
> printers in the other set belong only to the other server.
> Then there would be still load balancing but there would be
> no longer the automated fail-safe printing functionality
> for those printers.
>
> Probably the section
> "Intrinsic design of CUPS for printing in the network" in
> http://en.opensuse.org/SDB:CUPS_in_a_Nutshell
> is also helpful here.
>
> Regarding "implicit classes" and security, also have a look at
> "What is Specific Regarding Firewall Setup for Printing" in
> http://en.opensuse.org/SDB:CUPS_and_SANE_Firewall_settings
>
>
> Kind Regards
> Johannes Meixner
> --
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>