Re: [libvirt] "state" drivers?
On Mon, Apr 13, 2009 at 11:39:45AM -0400, Laine Stump wrote:
I'm looking through the network driver, and see the
"state" driver
registered. Several other drivers also register a state driver. What is
this used for? It looks like it's handling a startup/shutdown at a more
basic level than then open/close in the network (storage/qemu/etc)
driver itself. Is it the case that things that should happen only once
as libvirtd is loaded/unloaded should be put in the state driver's
Startup/shutdown?
The 'state' driver is for things which need to maintain global state
within the libvirtd daemon. The QEMU and network drivers both
maintain state in the libvirtd daemon. The Xen driver does not since
its all delegated to XenD.
It seems possible that these callouts may be unnecessary in my case,
since I'll be modifying the OS's own interface config, so the interfaces
will already be up and running by the time libvirtd starts, and should
remaining running after libvirtd is unloaded. (as for
initializing/shutting down netcf, this may be useful for shutting it
down before exit, but its init should probably only be called on demand
if someone actually calls a virInterface* function -otherwise we're
using up resources for nothing.
Your intuition is correct. There is no need for you to maintain a stateful
driver, since on each API call it'll simply directly read / write the
underlying host OS ifcfg-XXX files (or equiv). There's no real state
the needs to be kept in libvirtd for network interfaces
Daniel
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