On 04/10/2013 06:40 AM, Luiz Capitulino wrote:
On Wed, 10 Apr 2013 06:24:11 -0600
Eric Blake <address@hidden> wrote:
- If you want to overwrite an existing snapshot, you could specify
the 'id' or the 'name' argument or both of them and also you will
have to use the 'force' argument
But the argument made in this thread is that QMP should _not_ have a
force argument. It should be a flat-out error in QMP to try to create a
snapshot with a conflicting name or tag; preferably with a distinct
error type. Higher-level apps (HMP savevm -f) would try to create; if
-f is not specified, the error is good enough; if -f is specified and
that particular error is returned, then HMP calls delete and then
re-tries the create. No 'force' argument needed at the QMP layer.
To avoid adding a new error class, the HMP command could query for the
snapshot name and delete it if it exists before creating the snapshot.
Atomic collision detection is nicer than having to pre-query - fewer QMP
calls in the common case. But you're right that none of the existing
ErrorClass categories fit the idea of "creation refused because name
would collide".