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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