[cups] Monitoring concurrent print jobs

[Dave Close]

I asked:

>I have a client using CUPS from an application which is licensed
>according to the number of concurrent print jobs. I think he's paid
>for more licenses than he actually needs. But trying to discover the
>actual number of concurrently active jobs (to any printer) has me
>stymied. The CUPS log files don't seem to provide enough information.
>
>It appears that most or all jobs start with a "Create-Job" entry in
>cups/access_log. Most or all also seem to end with a "Send-Document"
>entry. But looking through several months of logs, those entries
>don't balance. I also see "Cancel-Job" entries that don't reference
>a printer, leaving me wondering. Sometimes I see several consecutive
>"Cancel-Job" entries where, near as I can tell, there should be no
>active jobs.
>
>Is there a better way to get this information besides parsing the logs?

=?UTF-8?B?SsO2cmcgVGjDvG1tbGVy?= answered:

>1st: looking into my /var/log/cups/access.log I only found balanced 
>Create-job and Send-document entries, always one by one... I remember 
>other entries in times I had some printer troubles, but this should be 
>the normal behavior.

Looking back about four months, I see 29235 log file entries,
12460 Create-Job, 12451 Send-Document, 4255 Cancel-Job. and 69
others. There's nothing to tie entries together so finding the
discrepancies would be tedious.

>2nd: I would set the variable MaxJobs in cupsd.conf to something large 
>enough. After that you have the jobfiles (and the documents) - on 
>linuxes they should be in /var/spool/cups. Jobfiles are named cXXXXXX, 
>the XXXXXX is the job number. In these jobfiles you found all 
>information about the job, so you can find the job creating user here, 
>which I believe is what you need to separate the jobs of the app. With 
>the time entries in the file there you should be able to find 
>concurrently active jobs, maybe with the "help" of the logfiles entries, 
>although (at least on my system, but maybe it's configureable) you don't 
>find the job number here...

I hadn't looked at the cXXXXX job files. Now that I have looked, my
collection only goes back a few days and they aren't easily searched
using text-based tools as they contain binary field lengths instead of
line endings. Time fields appear to be binary seconds since the epoch.
The only tie to access logs is the printer name and the times. Since I
have so few samples, the effort to parse them doesn't seem worthwhile.

But I was shocked to see that every one of them reports the printer-uri
as "ipp://...:631/...". This is shocking because there are no such URIs
in printers.conf. All printers are defined as "socket://". Although I
know that all of the printers are capable of handling IPP, converting
printers.conf is planned but not yet implemented.

In general, I think the usefulness of CUPS logs could be significantly
improved. But then, I was hoping someone might have already produced a
set of tools to deal with them.
-- 
Dave Close, Compata, Irvine CA      "A Conservative Government
dave at compata.com, +1 714 434 7359    is an organised hypocrisy."
dhclose at alumni.caltech.edu             -- Benjamin Disraeli