Re: [Xen-devel] [libvirt] [PATCH] libxl: open libxl log stream with libvirtd log_level

[Marek Marczykowski-GÃrecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Tue, Sep 15, 2015 at 11:21:00AM -0600, Jim Fehlig wrote:
> Daniel P. Berrange wrote:
> > 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@xxxxxxxx>
> >>>> ---
> >>>>  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"
> >   
> 
> Ah, good idea. I'll look into it.

Is it done anywhere? If not, how can I help?

This the above change (setting libxl log level to libvirtd global one),
makes almost impossible to get libxl debug, because the rest of libvirtd
trashes the logs (hundreds virEvent* and virObject* messages, at
"info"(!) level).

-- 
Best Regards,
Marek Marczykowski-GÃrecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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