[libvirt] Re: [PATCH 2/3] Introduce monitor 'wait' command

Daniel P. Berrange berrange at redhat.com
Wed Apr 8 14:33:35 UTC 2009

On Wed, Apr 08, 2009 at 09:16:43AM -0500, Anthony Liguori wrote:
> The wait command will pause the monitor the command was issued in until a new
> event becomes available.  Events are queued if there isn't a waiter present.
> The wait command completes after a single event is available.
> Today, we queue events indefinitely but in the future, I suspect we'll drop
> events that are older than a certain amount of time to avoid infinitely
> allocating memory for long running VMs.
> To make use of the new notification mechanism, this patch introduces a
> qemu_notify_event() API.  This API takes three parameters: a class which is
> meant to classify the type of event being generated, a name which is meant to
> distinguish which event in the class that has been generated, and a details
> parameters which is meant to allow events to send arbitrary data with a given
> event.

Perhaps we should have the ability to turn on/off events, via a 'notify EVENT'
command, and a way turn off the prompt on the channel used for receiving

So if I was interested in RTC change, and VNC client connection events, on
the main monitor command channel we'd do:

  (qemu)  notify rtc-change
  rtc-change notification enabled
  (qemu)  notify vnc-client
  vnc-client notification enabled

And then in the 2nd monitor channel, a single 'wait' command would turn
off the monitor prompt and make the channel dedicated for just events,
one per line

  (qemu) wait
  rtc-change UTC+0100
  vnc-client connect
  vnc-client disconnect
  vnc-client connect
  vnc-client disconnect

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