libvirt users - Feb 2012 - Bug? virGetLastError() returns NULL after virDomainCreate() if Domain running already

Hi,

As the subject line indicates, when I'm calling virDomainCreate() to start a
defined domain, and that command fails because the domain is already running at 
that point, virGetLastError() will return NULL, instead of a proper pointer to 
an error code.
Libvirt will, however, print an error to the console:

libvir: QEMU error : Requested operation is not valid: domain is already 
running

This looks like a bug to me, and I'm fairly certain that earlier version
would
return an error code of VIR_ERR_OPERATION_INVALID at that point. Or maybe that 
was just virDomainDestroy(), and I'm just blindly assuming that 
virDomainCreate() will work analogously...

Anyway, no error code is bad, because I can't tell what happened.

This is version 0.9.8. I couldn't find anything about this issue in the 
changelogs for 0.9.9 and 0.9.10, so I'm assuming the issue has not been 
addressed since.

	Guido

On 02/22/2012 07:06 AM, Guido Winkelmann wrote:
> Hi,
> 
> As the subject line indicates, when I'm calling virDomainCreate() to
start a
> defined domain, and that command fails because the domain is already
running at
> that point, virGetLastError() will return NULL, instead of a proper pointer
to
> an error code.
> Libvirt will, however, print an error to the console:
> 
> libvir: QEMU error : Requested operation is not valid: domain is already 
> running
Any return of NULL without a last error set is a bug.  I'm trying to
chase this down, and hope to have a patch soon.
> 
> This looks like a bug to me, and I'm fairly certain that earlier
version would
> return an error code of VIR_ERR_OPERATION_INVALID at that point. Or maybe
that
> was just virDomainDestroy(), and I'm just blindly assuming that 
> virDomainCreate() will work analogously...
> 
> Anyway, no error code is bad, because I can't tell what happened.
If the create xml matches the already running xml, we could perhaps
argue that this should return the already-running domain instead of
NULL.  But that seems like it might be more confusing, as we must not
allow a second create attempt with xml that doesn't match what is
currently running (you have to use hotplug apis to alter a running
domain xml, not re-creation).

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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