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Re: [libvirt] RFE: virConnectListAllDomains()

On Fri, May 18, 2012 at 6:52 PM, Eric Blake <eblake redhat com> wrote:
Use of virConnectListDomains() and virConnectListDefinedDomains() is:

1. inherently racy.  A domain can change between active and inactive
between two back-to-back calls, and thus be entirely skipped or
enumerated twice when concatenating lists.

2. painful to use.  ListDomains gives ids, ListDefinedDomains gives
names, and the user must then call virDomainLookupByID() and
virDomainLookupByName() to convert into UUIDs.

3. requires pre-allocation.  The user must call virConnectNumOfDomains()
then over-allocate before calling virConnectListDomains(), in order to
guarantee that the list size didn't change between the two calls.

This is a proposal for a new API that addresses all three points - by
returning virDomainPtr rather than id or strings, the UUID of each
domain can be grabbed in one shot.  By consolidating things into a
single API call, there is no race in trying to piece together the
complete list.  By having libvirt allocate the resulting array, rather
than making the caller pre-allocate, the user doesn't have to worry
about a race between getting a count and using that count.  It also
provides the convenience of returning smaller lists based on various
filtering groups.

Thoughts before I expand this API and add the actual implementation?

Very nice idea.  Will the perl wrapper, Sys-Virt, be updated to expose this new C api?


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

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