Re: [Qemu-devel] [PATCH 6/9] log: log QMP commands and replies

[Daniel P. Berrange]

On Mon, Mar 14, 2016 at 03:33:53PM +0100, Paolo Bonzini wrote:
> 
> 
> On 14/03/2016 12:21, Denis V. Lunev wrote:
> > From: Pavel Butsykin <address@hidden>
> > 
> > This log would be very welcome for long-term diagnostics of the system
> > in the production. This log is at least necessary to understand what
> > has been happened on the system and to identify issues at higher-level
> > subsystems (libvirt, etc).
> > 
> > These messages will be quite useful to understand how things are going.
> 
> There is now a logging mechanism for qemu-char.c.  Have you looked into
> making libvirt provide a QMP log based on it?
> 
> The timestamping of patch 9 could be useful for character devices as well.

libvirt QEMU driver already has logging support for recording all the data
it both sends and receives over QMP, which should be sufficient for any
day to day troubleshooting of QMP issues. So I doubt duplicating that
info from QEMU side too is really beneficial for debugging issues when
libvirt is in use.

In libvirtd set

  log_filters="1:qemu_monitor"

and it'll capture everything on the QMP monitor in the default libvirtd
log file.

The QMP data is also fed into the libvirt tracing backend, so you can
write systemtap scripts that hook on any QMP message, reply or event.
We ship a sample monitoring script examples/systemtap/qemu-monitor.stp
for this too.

Regards,
Daniel
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