[libvirt] RFC: what are the requirements to domain id

[Nikolay Shirokovskiy]

Hi, all.

  Domain id is somewhat required feature for hypervisors: virsh list prints
them by default and active/inactive distinction is based on this id value
analysys. But other than -1 is reserved for inactive domains there is no
further requirements for it, one can happily keep them 0 for active domains.

  Looks like some drivers use process pids for this purpose. Qemu driver use
its own incrementing counter and domain ids endure libvirtd restart. Vz do not
provide a suitable value so the question arises can some simple id
implementation be good enough? By simple I mean to keep counter as long as
daemon lives and do not introduce any additional persistent state. As I said
before there is basically no option to not to support it.

A more profound question is what is this id for?  How it is supposed to be used?

Nikolay