[libvirt] [PATCH 2/4] virsh: Add timestamps to events

[Jiri Denemark]

On Mon, Dec 21, 2015 at 16:25:56 +0100, Andrea Bolognani wrote:
> On Mon, 2015-12-21 at 11:04 +0100, Jiri Denemark wrote:
> > 
> > @@ -12154,7 +12155,16 @@ virshEventPrint(virshDomEventData *data,
> >      if (!data->loop && *data->count)
> >          goto cleanup;
> >  
> > -    vshPrint(data->ctl, "%s", msg);
> > +    if (data->timestamp) {
> > +        char timestamp[VIR_TIME_STRING_BUFLEN];
> > +
> > +        if (virTimeStringNowRaw(timestamp) < 0)
> > +            timestamp[0] = '\0';
> > +
> > +        vshPrint(data->ctl, "%s: %s", timestamp, msg);
> > +    } else {
> > +        vshPrint(data->ctl, "%s", msg);
> > +    }
> 
> So the timestamp is not really for the moment the even occurred,
> rather the moment it was printed. I don't know if the difference is
> something we should really care about.

The main reason for adding the timestamp was to be able to look at the
output and see, e.g., that a few events came very close to each other,
then there was a 30s delay before another event came. I don't think
getting the exact timing from libvirtd would be useful for anything.

> The signature for virConnectDomainEventGenericCallback, unlike the one
> for virConnectDomainQemuMonitorEventCallback, does not provide timining
> information. Would it be a good idea to maybe have a new kind of
> callback for generic events that includes such information, instead of
> using the timestamp from when we printed the message?

It's not just about the callback signature, each event would have to
provide the timestamp... IMHO it's not worth the effort at all.

> What about having qemu-monitor-event support --timestamp as well? I know
> the timing information are already part of the output, but we could use
> the same format used here (much more readable) and avoid duplicating
> them in the message. POC attached.

qemu-monitor-event is designed to provide more-or-less raw data from
QEMU. Personally, I'd leave it alone, but I don't feel strongly either
way :-) The main reason for doing it this way was laziness (what a
surprise!).

Jirka