Re: [libvirt] PATCH: Improve error reporting for operations on inactive domains

If you try todo an operation on an inactive QEMU guest which is not applicable, eg ask to pause an inactive guest, then you currently get a useless message # virsh suspend demo error: Failed to suspend domain demo error: invalid domain pointer in no domain with matching id -1 There are two issues here - The QEMU driver is mistakenly doing a lookup-by-id when locating the guest in question. It should in fact do lookup-by-uuid for all APIs since that's the best unique identifier. - It was using VIR_ERR_INVALID_DOMAIN code instead of VIR_ERR_NO_DOMAIN code, hence the 'invalid domain pointer' bogus message. This patch changes all QEMU APIs to lookup based on UUID, and use the correct VIR_ERR_NO_DOMAIN code when reporting failures.

You now get to see the real useful error message later in the API where it validates whether the guest is running or not # virsh suspend demo error: Failed to suspend domain demo error: operation failed: domain is not running One thing I'm wondering, is whether we should introduce an explicit error code for operations that are not applicable.

eg, instead of giving VIR_ERR_OPERATION_FAILED, we could give back a code like VIR_ERR_OPERATION_INVALID. This would let callers distinguish real failure of the operation, vs the fact that it simply isn't applicable for inactive guests.