Re: [libvirt] [PATCH 0/5] Support embedding the QEMU driver in client apps directly

On Fri, May 17, 2019 at 13:24:52 +0100, Daniel Berrange wrote: Few thoughts: I like this approach in general. We were bound to lose the full host view of VMs started by libvirt shim sooner or later anyways as people would want to stuff the libvirtd into a container. Few things we should consider prior to making this a feature: 1) We should introduce a hard limit that the 'root' directory must not be created by a library version greater than we are running right when connecting. This is to prevent downgrades and thus all the problems with them right upfront. 2) The library needs to make sure that the event loop is registered in this case and ideally also make sure that it has run so that we avoid problems with stuck instances. 3) The capability caching is not leveraged when creating a new instance of the 'root'. 4) Internally we'll need to relax few checks in the migration region as igrating to a different "root" will certainly make sense now. 5) It would be cool to have a way to virConnectDomainEventRegisterAny prior to actually opening the connection. This would allow e.g. get the events for block jobs which terminated while the app was away for some reason so that it does not have to poll. 6) We need to write a doc setting the expectations how to use this in the APP. (Clarify threading and that users can't avoid domain jobs etc. [1]) 7) We should get of rid of the 'autostart' feature for 'embed' type connections. 8) Some kind of label depending on 'root' should be used in logs as things may log into the same place and that would be a pain to debug. This implies ... [2] [...] [1] Or that removing the directory may e.g. get rid of some state which may be needed like snapshot metadata etc. [1] ... that this is ideally supported as well. It'll be surprising if your tests spawn VMs which will infiltrate your 'default' network for example. We might want to also have a way how to specify this during connection. Also this new program since it's advertised as 'copy this into your code' should avoid using virAsprintf for constructing the URI.