Open Stack

Hi folks!

I want to raise something we haven't apparently thought about when working on 
the driver composition reform.

For example, an iRMC patch [0] replaces 'pxe' boot with 'irmc-pxe'. This is the 
correct thing to do in this case. They're extending the PXE boot, and need a new 
class and a new entrypoint. We can expect more changes like this coming.

However, this change is breaking for users. Imagine a node explicitly created with:

  openstack baremetal node create --driver irmc --boot-interface pxe

On upgrade to Pike, such nodes will break and will require manual intervention 
to get it working again:

  openstack baremetal node set <UUID> --boot-interface irmc-pxe

What can we do about it? I see the following possibilities:

1. Keep "pxe" interface supported and issue a deprecation. This is relatively 
easy, but I'm not sure if it's always possible to keep the old interface working.

2. Change the driver composition reform to somehow allow the same names for 
different interfaces. e.g. "pxe" would point to PXEBoot for IPMI, but to 
IRMCPXEBoot for iRMC. This is technically challenging.

3. Only do a release note, and allow the breaking change to happen.

WDYT?

[0] https://review.openstack.org/#/c/416403