Bug#758626: cups-browsed: uses a lot of CPU on a busy network

[Julian Gilbey <jdg@debian.org>]

Hello Till!

On Fri, Oct 31, 2014 at 03:25:05PM +0100, Till Kamppeter wrote:
> I by myself have never tested cups-browsed with that many printers or
> otherwise very noisy networks. It is also the first time that someone
> reports that cups-browsed takes a lot of CPU.
> 
> cups-browsed is running an event loop and if an event (= broadcast
> signal from local avahi-daemon or from remote CUPS server) happens, a
> callback function to create, update, or remove a print queue is executed.
> 
> Important to know is also what kind of broadcasting the remote servers
> are doing. Are they running newer CUPS versions and so using Bonjour for
> broadcasting (cups-browsed is then triggered by the local avahi-daemon)
> or are these older servers using CUPS broadcasting (cups-browsed uses
> the legacy CUPS browsing facility then)?
> 
> Can you deactivate CUPS browsing via cups-browsed.conf? If some printers
> go away on your local system then you indded have servers using the old
> method. Does the system load caused by cups-browsed go down now? Perhaps
> upgrading old servers to have all broadcasting being Bonjour could help.

I modified cups-browsed.conf by changing the line

BrowseRemoteProtocols dnssd cups

to read

BrowseRemoteProtocols dnssd

and then restarted cups-browsed.  I now have negligible load from
cups-browsed and no printers found.

> Is there a lot of Bonjour broadcasting in your network, also from other
> devices, like file servers or so? You can see this running the
> "avahi-discover" command.

There is some amount of broadcasting, but it seems to be at a rate of
one broadcast every few seconds.  I don't see any printers being
broadcast.

> Is your local machine sharing CUPS printers? Did you turn on the legacy
> CUPS broadcasting of your local cups-browsed to share to old clients?
> Try to turn this off and in case of success, update the CUPS on these
> clients.

I don't believe that I'm sharing any printers.  (I don't have any
locally connected printers, for a start.)

Thanks!

   Julian