Unnecessary resource usage in CUPS

[Kurt Pfeifle]

> With no printer attached, cups will poll for a printer every 30 seconds. It=
>  will do this even if there are no print jobs in the queue or other request=
> s for the printer. With logging enabled at a high level, this significantly=
>  increases system power consumption, since it prevents disks from spinning =
> down. With logging disabled, it still prevents deeper system sleep states, =
> prevents cups from being swapped out to disk, and goes from major problem t=
> o minor nuisance. This is a problem with laptops, which are frequently disc=
> onnected from power and printers to travel. Cups behavior decreases battery=
>  life. Cups should not poll for printers unless there is a specific need to=
>  talk to the printer. Furthermore, with USB devices, it should not poll at =
> all, but rather wait for a USB device connect event. This bug report comes =
> from Cups 1.2.7. I do not know
> whether it still applies to more recent versions. I furthermore do not
> know if it has been reported before.=20


CUPS does not poll the printers.

CUPS *may* poll other CUPS servers ("BrowsePoll" setting in cupsd.conf). However, this is not enabled by default. If your setting has this enabled, it is you or your system's admin who needs to change it again once you disconnect from the power plug and/or the network.

Also, you can control the BrowsePoll frequency and caching of its results via "BrowseInterval" and "BrowseTimeout" settings.

USB-connected printers are only discovered if you click on the the "/admin" location link in the web interface, or run specific commands like "lpinfo -v".

If you want to save resources you shouldn't enable "logging at a high level" either.