[libvirt] latency between LIFECYCLE event and notification generation

[Daniel P. Berrange]

On Tue, May 14, 2013 at 11:56:48AM +0530, nishant burte wrote:
> Thanks Eric and Daniel for the response.
> For the 2nd question, let me elaborate more.
> 
> >
> > 2. Second question is, can someone please explain what are the sequence of
> > steps happen between a VM going down and the notification is generated?
> 
> Lets say, the VM crashed. The question is, how does qemu (or hyperviser )
> come to know about it? and how does it generate notification?

Libvirt has a connection to the QEMU monitor socket. So when QEMU dies,
the monitor socket triggers POLLHUP or POLLERR in libvirt's event loop,
at which point libvirt transitions the VM state to shutoff. 

Daniel
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