On Mon, Aug 02, 2021 at 14:20:44 +0200, Vojtech Juranek wrote:
Hi, as a follow-up of BZ #1883399 [1], we are reviewing vdsm VM migration flows and solve few follow-up bugs, e.g. BZ #1981079 [2]. I have couple of questions related to libvirt:
* if we run disk extend during migration, it can happen that migration finishes sooner than disk extend. In such case we will try to set disk threshold on already stopped VM (we handle libvirt event that VM was stopper, but due to Python GIL there can be a delay between obtaining appropriate signal from libvirt and handling it). In such case we get libvirt VIR_ERR_OPERATION_INVALID when setting disk threshold. Is it safe to catch this exception and ignore it or it's thrown for various reasons and the root cause can be something else than stopped VM?
The API to set the block trheshold level can return the following errors including cases when it can happen: VIR_ERR_OPERATION_UNSUPPORTED <- unlikely new qemu supports it VIR_ERR_INVALID_ARG <- disk was not found in VM definition VIR_ERR_INTERNAL_ERROR <- on error from qemu Thus VIR_ERR_OPERATION_INVALID seems to be safe to ignore in your specific case, while not ignoring others can be used to catch problems.