Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2)

Zachary Amsden wrote: You know, as silly as this little exercise is, it actually has some interesting points. MUDs present a prompt showing the current status of the player; hit points, mana, and V (movement points) are the default display here, but typically you can customize the prompt to include many variables and syntax to make it easy for you to parse... and simply sending a NULL cmd (CR/LF) gets you a status update whenever you want. Now, that's sort of the same thing a virtualization management tool might want to monitor in the event of out-of-band asynchronous events - number of online CPUs, RAM, and VM power status. Add command tagging so you can associate responses to specific commands, and you've got a very powerful monitor in a single I/O channel. Personally, I think relying on asynchronous events to provide reliable status is a bad idea. Management connections can and will get disconnected, buffers will get filled and event notifications will be dropped. Having a status line that is pollable by the client allows easy access to all this information whenever it is needed.. such as an error condition. Trying to stop an already stopped VM might confuse a management program when it fails, and leaving the online status indeterminate isn't a good thing to present to the user, but if a status line is available, it is very convenient, easy to use, and never loses information. And it's really useful when your cleric's job is to hit enter to get leader status as quickly as possible so they can recall the berzerker who is buffing the mob before HP run out and they end up dead. Losing XP from dying sucks, it takes days to get that back. Zach