Mark Goddard <mark@stackhpc.com> writes:
The thinking behind upgrading one cell at a time is to limit the blast radius if something goes wrong. You suggest it would be better to roll all cell conductors at the same time though - do you think it's safer to run with the version disparity between conductor and computes rather than super- and cell- conductors?
Yes, the conductors and computes are built to work at different versions. Conductors, not so much. While you can pin the conductor RPC version to *technically* make them talk, they will do things like migrate data to new formats in the cell databases and since they *are* the insulation layer against such changes, older conductors are going to be unhappy if new conductors move data underneath them before they're ready.
Here is the line that made me think policies are required in conductors: https://opendev.org/openstack/nova/src/commit/6d5fdb4ef4dc3e5f40298e751d966c.... I guess this is only required for cell conductors though?
No, actually more likely to be the superconductors I think. However, it could technically be called at the cell level so you probably need to make sure it's there. That might be something left-over from a check that moved to the API and could now be removed (or ignored). --Dan