[Libvirt-cim] [PATCH 0 of 2] [RFC] ComputerSystemModifiedIndication

[Heidi Eckhart]

Dan Smith wrote:
> JG> Is there a mechanism for indications reporting errors, beyond
> JG> CU_DEBUG'ing "help" and hoping to recover?
>
> I would expect that the answer will be that there isn't much that can
> be done.  A CU_DEBUG() indicating the issue is certainly required, but
> I'm not sure what else we have.
>   
CU_DEBUG() is the providers possibility to report an error. A mechanism 
to report a failure in the indication processing itself to the 
subscriber of the ComputerSystemModfiedIndication can not be done via 
the ComputerSystemModifiedIndication. This indication will only be 
thrown, if all went fine. So an indication in general is only reporting 
positive results - means, if the filter requirement is fulfilled, the 
indication is thrown. To monitor a failing indication processing an 
additional indication provider would be necessary. This one would then 
handle "please inform me, if something in the processing of the 
ComputerSystemModfiedIndication failed". So a client would need to 
subscribe 1) to the ComputerSystemModifiedIndication to get informed of 
the modification and 2) to the AlertIndication monitoring the indication 
processing to get informed of a failing processing.
> I tend to think that indications are mostly for convenience and
> optimization, to avoid pinging the providers unnecessarily, in which
> case an error wouldn't be catastrophic.  Multiple clients monitoring a
> single provider would use them to notice when the other makes a
> change.
>   
I absolutely agree. For now I would say, its more important to have the 
ComputerSystemModifiedIndication. But at a later point in time - an 
indication provider who reports processing failures could be added as a 
feature.

-- 
Regards

Heidi Eckhart
Software Engineer
IBM Linux Technology Center - Open Hypervisor