[Spice-devel] RFC: Lightweight tracing mechanism

[Jonathon Jongsma]

On Fri, 2017-06-09 at 12:11 -0400, Marc-André Lureau wrote:
> > 
> 
> ----- Original Message -----
> > 
> > > On 9 Jun 2017, at 17:16, Jonathon Jongsma <jjongsma at redhat.com>
> > > wrote:
> > > 
> > > On Fri, 2017-06-09 at 10:59 +0200, Christophe de Dinechin wrote:
> > > > > > What I see on the thread:
> > > > > > - log categorization. This was similar to Djasa bug but I
> > > > > > think
> > > > > > he just
> > > > > >   proposed to use domains in the glib log sense;
> > > > 
> > > > Punchcard analogy: “Printer sheet categorization. This was
> > > > similar to
> > > > the report that Djisktra had taken McCarthy's listing by
> > > > mistake"
> > > > 
> > > > I thought it was a good idea to derive glib log domains
> > > > automatically
> > > > from spice-traces.def. So it’s there in the branch now. That
> > > > being
> > > > said, as noted above, glib does linear searches on domain
> > > > names, so
> > > > this does not scale well. In the long term, we may want to have
> > > > a
> > > > separate field in a structured log.
> > > 
> > > 
> > > Responding only to this point for the moment: I don't think using
> > > multiple glib logging domains is necessarily desirable. We
> > > already use
> > > several logging domains, but the vast majority of logging
> > > statements
> > > within each project use a single domain. In spice-server, that
> > > primary
> > > log domain is "Spice", and in spice-gtk that domain is "GSpice".
> > > spice-
> > > server also has some additional domains like "SpiceWorker" and
> > > "SpiceDispatcher". spice-gtk also has GSpiceController (which
> > > isn't
> > > really used much these days).
> > > 
> > > The problem is that both spice-server and spice-gtk have a way to
> > > enable debugging with an environment variable. But the code for
> > > enabling the debugging only actually enables the primary domain.
> > 
> > The ‘traces’ branch enables all trace-related domains if you enable
> > debug.
> > 
> > > So anything that is logged under a different domain does not get
> > > enabled.
> > > (In fact, spice-gtk has 2 ways to enable logging with an
> > > environment
> > > variable but one of the methods is the same one used for spice-
> > > server,
> > > but it doesn't work since it actually enables logging for the
> > > "Spice"
> > > domain which spice-gtk doesn't use.) I'm hoping to send some
> > > patches to
> > > clean up this mess soon.
> > 
> > Ah, so I was not the only one thinking this was a mess :-)
> 
> The mess comes because spice-gtk and spice server used different
> logging, when spice didn't depend on glib.
> 
> The cleanup isn't over I suppose (Christophe F. did the move to glog
> in spice-common). 
> 
> I don't get the problem with spice-gtk logging though.
> 


Yes, there are historical reasons. And "mess" was an exaggeration. But
in the process of consolidating the implementations, we seem to have
introduced some inconsistencies. I'll send more details soon, I hope.