[libvirt-users] domain reinitalization detection

[Matczak, KrzysztofX]

One additional question regarding event listening:  
How to control timeout on call to   virEventRunDefaultImpl  in event loop ? Default timeout  when there are no events is something like 5s , which is way too much for my application. I can't find related examples and API docs are not quite straightforward in that matter

thanks
Krzysztof

> Listen to the events
I guess that would require running my own polling thread, right ? I wanted to avoid that ...

Thanks for help


On 06.03.2017 14:14, Matczak, KrzysztofX wrote:
> Hello
> 
> I'm trying to find out how to detect if domain was destroyed and brought up between two time moments,  let's call it reads. 
> So far the best approach I could find is to compare domain ID from previous and current read. 
>  And this is my first question : is that reliable solution ? Or do you know any better  ?

Listen to the events. If domain is destroyed/started libvirt fires up an event. The domain ID is not necessarily unique. For instance:

a) start a domain and assume it's the first one started. It will have ID=1.
b) destroy it.
c) restart libvirtd.
d) start the domain again - it will have ID=1.

This applies to qemu driver, other drivers might have different meaning for domain IDs - e.g. LXC driver reports PID of the container's init in which case you can make no assumptions about it.

> 
> And related question is how to  resolve virDomainPtr into domain ID ?

virDomainGetID().

> The only verified  way  of getting domain ID I know is  to memorize it's UUID, then  call virConnectListDomains , then iterate over all returned domain IDs and resolve each one's pointer  using virDomainLookupByID , then  get  UUID  by virDomainGetUUIDString  get domain ID of matching UUID's .  
> It seems too complex  and I  expect noticeable performance overhead, so looking for something lighter.  
> 
> I'm trying to get current domain ID using  API function : 
> 
> char *    virDomainGetMetadata (virDomainPtr domain,  int type,  const char * uri, unsigned int flags)
> 
> I'm  not sure it's  relevant  function, since domain ID is contained not in metadata subsection but in opening <domain> markup. 
> In fact  I wasn't even able to get any data using that function call since I don't know how to construct valid URI. Do you know any doc or examples explaining that ?  

Documentation might come handy:

http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainSetMetadata
http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainGetMetadata

or just look into our test suite:

http://libvirt.org/git/?p=libvirt.git;a=blob;f=tests/metadatatest.c;h=55dc841254bcfda0742d22580723bf4acac172b4;hb=HEAD

Michal
--------------------------------------------------------------
Intel Research and Development Ireland Limited Registered in Ireland Registered Office: Collinstown Industrial Park, Leixlip, County Kildare Registered Number: 308263


This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.


_______________________________________________
libvirt-users mailing list
libvirt-users at redhat.com
https://www.redhat.com/mailman/listinfo/libvirt-users
--------------------------------------------------------------
Intel Research and Development Ireland Limited
Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263


This e-mail and any attachments may contain confidential material for the sole
use of the intended recipient(s). Any review or distribution by others is
strictly prohibited. If you are not the intended recipient, please contact the
sender and delete all copies.