[libvirt] [PATCH] libxl: open libxl log stream with libvirtd log_level

[Daniel P. Berrange]

On Tue, Sep 15, 2015 at 10:57:50AM -0600, Jim Fehlig wrote:
> Daniel P. Berrange wrote:
> > On Tue, Sep 15, 2015 at 09:26:23AM -0600, Jim Fehlig wrote:
> >   
> >> Instead of a hardcoded DEBUG log level, use the overall
> >> daemon log level specified in libvirtd.conf when opening
> >> a log stream with libxl. libxl is very verbose when DEBUG
> >> log level is set, resulting in huge log files that can
> >> potentially fill a disk. Control of libxl verbosity should
> >> be placed in the administrator's hands.
> >>
> >> Signed-off-by: Jim Fehlig <jfehlig at suse.com>
> >> ---
> >>  src/libxl/libxl_conf.c | 18 +++++++++++++++++-
> >>  1 file changed, 17 insertions(+), 1 deletion(-)
> >>     
> >
> > ACK, this makes sense as default behaviour. As a future enhancement
> > you might also consider supporting a config setting in /etc/libvirt/libxl.conf
> > to explicitly control the libxl library logging behaviour independantly.
> >   
> 
> I had actually thought of adding it there first, but then took this
> approach assuming it would be more receptive upstream :-). Personally,
> I'm on the fence. I like the idea of a single knob to control log level
> throughout the daemon, making it a bit easier on admins. On the other
> hand, individual knobs are more friendly to those pouring through logs.
> I can add a knob in libxl.conf if preferred.

After thinking about it some more, I could actually see value in
create a dedicated virLogSource() instance, solely for libxl
library messages. If we then created a virLogSourceGetPriority()
method, you could query that to see if to turn on logging for
the libxl library. That would ultimately allow you to turn on
debug for just the libxl library if desired, eg

 static virLogSource virLogLibXL = {
     .name = "libxl.libxl_library",
     ....
 }

LIBVIRT_LOG_FILTERS="1:libxl_library"

Regardless we should just merge your current patch right now.

Regards,
Daniel
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