[cups] Monitoring concurrent print jobs

[Bryan Mason]

On Mon, 2023-06-19 at 17:03 -0700, Dave Close wrote:
> ... 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.
> 
> Is there a better way to get this information besides parsing the
> logs?

The lpstat command can give you a lot of information on jobs.  

"lpstat -p" gives you a list of all the print queues and their
statuses.  If one of the queues is actively processing a job, the
status will begin with something like:

  printer rlap now printing rlap-12.

"lpstat -o" will give you a list of all non-completed jobs in all print
queues.

"lpstat -W completed -o" will give you information on completed jobs,
and that information includes the date/time the job was submitted, but
I don't think it includes a timestamp for job completion.  The output
of this command is also limited to the number of jobs for which CUPS
has history in /var/spool/cups.

If you have "Loglevel info" (or "LogLevel debug") set in cupsd.conf,
then the CUPS error log contains "Queued on" and "Job completed"
messages with timestamps that will let you know when the job was
submitted (when the Create-Job request was sent) and the time the job
was completed.  For example:

# journalctl --no-host -u cups.service | grep -E '(Queued on)|(Job
completed)'
Jun 20 13:07:18 cupsd[742]: [Job 7] Queued on "rdn" by "root".
Jun 20 13:07:18 cupsd[742]: [Job 7] Job completed.
Jun 20 13:08:31 cupsd[3770]: [Job 8] Queued on "rdn" by "root".
Jun 20 13:08:31 cupsd[3770]: [Job 8] Job completed.

>From that you should be able to calculate the number of jobs active at
any given time.

~ Bryan