[libvirt] Re: [PATCH 2/3] Introduce monitor 'wait' command
Gerd Hoffmann
kraxel at redhat.com
Wed Apr 8 15:03:26 UTC 2009
On 04/08/09 16:33, Daniel P. Berrange wrote:
> 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
> events.
That would nicely solve the "queue events indefinitely" issue. By
default no events are generated. Apps which want receive them (and thus
receive them) can enable them as needed.
> 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 192.46.12.4:9353
> vnc-client disconnect 192.46.12.4:9353
> vnc-client connect 192.46.12.2:9353
> vnc-client disconnect 192.46.12.2:9353
IMHO this is more useful than having "wait" just get one event. You'll
need a dedicated monitor channel for events anyway, so with
one-event-per-wait the management app would have to issue wait in a loop.
BTW: "wait" is quite generic. Maybe we should name the commands
notify-*, i.e. have
notify-enable $class
notify-disable $class
notify-getevents
cheers,
Gerd
More information about the libvir-list
mailing list