[libvirt] [PATCH v2 2/6] virsh: add support for VIR_DOMAIN_CONSOLE_FORCE flag

[Peter Krempa]

Dňa 14.12.2011 1:14, Eric Blake  wrote / napísal(a):
> Hmm, wondering about back-compat - what happens if we are talking to an
> older libvirt that does not know VIR_DOMAIN_CONSOLE_FORCE, but also
> which does not prevent multiple connections when flags==0?  At first
> glance, it looks like we're stuck - there's no useful way to tell if a
> console was already in use.
Yes, we would end up in a state like when you try it now.

> But maybe we could add a new API, to allow probing whether a console is
> in use.  If the API exists, then we know whether the console is in use
> (and we also know whether --force will work); if the API does not exist,
> the we know we are talking to an older server that multiplexes
> connections.  Maybe we should have:
>
> virsh console domain --safe =>  refuse to connect unless connection is
> safe (fails on older servers)
> virsh console domain --force =>  force connection (fails on older servers)
> virsh console domain =>  existing behavior (connects on older servers,
> even if it corrupts connection, and safely connects on newer servers)

Yes, that's definitely a good idea.

> that is, I'm thinking it might be worth it to add a new --safe option
> that lets the user probe (via a new API virDomainConsoleInUse(dom,
> dev_name, flags)) whether the attempt will be safe.

I was thinking about adding another flag. With that flag specified, the 
virDomainConsoleOpen function would return success without any 
operation, confirming, that the server is capable of handling console 
connections in a safe way. The client could then open the connection 
calling this function again.

What do you think about this option?

Peter