[ovs-discuss] [PATCH] mgmt: Local config changes can cause update failures from controller.

[Ben Pfaff]

Justin Pettit <jpettit at nicira.com> writes:

> If ovs-vswitchd.conf is locally modified, but ovs-vswitchd is not told
> to reload it, updates from the controller will be refused.  This is
> because we attempt to lock the file with SHA-1 snapshot of the config
> file.  Since the hashes will not match, we will never be able to lock
> the file, and all remote updates will fail.  There is not much that can
> be done about this, since we don't want to presume the current state of
> the file is correct, since it could be in the process of being updated.

ovs-vswitchd.conf is supposed to be updated atomically using
"rename".  If that is done properly (and I believe that we do so
everywhere), then its contents should always be consistent, and
it always makes sense to reload it if it has changed.  We don't
do so now for at least two reasons: laziness (ovs-vswitchd
doesn't bother to look for changes) and because we might as well
let a series of individually atomic changes be reloaded in a
single step.

So I think that a better approach would be to log a warning and
then force ovs-vswitchd to reconfigure itself.