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.
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 (qemu)
So you want to mask out event types? I think you could do this with the actual wait command either inclusively: (qemu) wait "rtc-change vnc-client" ... Or exclusively: (qemu) wait -x "rtc-change vnc-client" ...
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
N.B. Right now, wait returns only a single event. This is because the output format is: (qemu) wait 1239200822.748241: vm-state: stop (qemu) But vm-state doesn't have any details, if it had details it would be: (qemu) wait 1239200822.748241: vm-state: stop The virtual machine has stopped. (qemu) Since everyone already parses commands like this, I think the format makes sense. It implies that the event dispatch code has to sit constantly issuing wait commands. In my next version of the patch, I expire old events (older than 10 minutes), and also add a -d flag to poll for events vs. wait. Regards, Anthony Liguori
Daniel
-- Regards, Anthony Liguori