On 08/14/2012 10:59 AM, Dmitry Guryanov wrote: > Hello, > > vmware, openvz and parallels driver, which was written with first two ones > as an example, get list of domains in virConnectOpen and then use it for > lookups and even for listing sometimes. This is not correct, because you > can make several connections to the same driver and changes, made in one > connection will not be visible to other. And you can also create or > destroy domains using native tools. > > So I think keeping list of domains in a stateless driver is a bad idea - > you should update this list each time when user requests some info. It's > better to retrieve needed data only when it requested, like in xenapi > driver. Yes, that sounds like a correct assessment. Unless there is some sort of API in the hypervisor that can be used to quickly tell if your local cache of information is still up-to-date. For example, with the qemu QMP monitor, every transaction incluses a monotonically transaction id; if libvirt were worried about multiple simultaneous clients on the monitor, we could still cache information and only invalidate the cache when a transaction id skips more than the 1 expected increment for a simple echo command. But I don't know if paralles, vmware, and/or openvz have anything like this, so you are right that it is probably better to reconstruct state on every call rather than relying on a cache that could be silently out of sync with the real hypervisor state.