Re: [libvirt] [PATCH v2 6/7] virsh: domstate: report detailed state if available

On 4/1/19 10:17 AM, Bjoern Walk wrote: > I intent to have the new API function superseed the existing one, so I > actually want to call virDomainGetStateParams() unconditionally and only > fall back to virshDomainState() when the new API is not there (so that > hopefully at some distant point in the future, we could deprecate the > old stuff). I understand that but consider the following scenario: a shell script that calls 'virsh domstate $dom' every so often. If we switch to new API then this will still fetch expected info for the client but also it will produce an error message logged at the server side (if it is old and doesn't support the new API). That's the main reason I think we should use new API only if necessary, i.e. if --info was requested. But if you still want to prefer the new API we should do it the proper way. That is something among these lines: if (virDomainGetStateParams() < 0) { if (!last_error || last_error->code != VIR_ERR_NO_SUPPORT) goto error; /* fallback */ if (virshDomainState() < 0) goto error; } Note that we have to check for the reason why vurDomainGetStateParams() failed and fallback on old API if and only if the new API is not supported.

> > Also, printing out some error message would be nice: > > If the new API is not available, I wanted to just silently have the old > behaviour. The domain state and reason can always be retrieve (by means > of the old API) only additional information could be missing. I am not > sure if we should error out if this is the case. I think we should. I mean, if I'd run 'virsh domstate --info' that means I am expecting some extended info on domain state. If I don't get it, isn't that a failure?