[libvirt] [RFC] Design executing commands from within domains

[Daniel P. Berrange]

On Tue, Aug 09, 2016 at 05:48:45PM +0800, Chen Hanxiao wrote:
> 
> At 2016-08-08 23:00:38, "Michal Privoznik" <mprivozn at redhat.com> wrote:
> >Dear list,
> >
> >while wiring qemu-ga into libvirt I've noticed that it has ability to
> >spawn commands inside guest. I haven't paid much attention to it then as
> >implementing libvirt <-> qemu-ga communication was more important. But
> >lately couple of requests on the list showed up where ability to spawn
> >various commands inside guests would be much appreciated (e.g. when
> >fetching some stats that HV can't know or has no support for yet -
> >free/df/..).
> >
> >When it comes to spawning commands we distinguish two modes: sync and
> >async. I think we should stick to this on the public API level too. Yet
> >better, we can have async APIs and the sync API would just be a wrapper
> >around async then.
> >
> 
> Cool!
> We should had a API than using qemu monitor command.
> 
> ...
> 
> >virStreamEventAddCallback(st, VIR_STREAM_EVENT_READABLE,
> >domainCommandCallback, ...);
> >
> >/* ... */
> >
> >virDomainCommandJoin(dom, cmd);
> >
> >virStreamEventRemoveCallback(con->st)
> >
> >virDomainCommandFree(cmd);
> >
> 
> Do we had timeout mechanism?
> Some command may hang for a long time in guest.

Yet another reason to not try to re-invent a mechanism for running shell
commands in libvirt API, and just run a shell service over a separate
virtio-serial port instead.

Regards,
Daniel
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