[openstack-dev] [nova][cells] Flavors and cells

Dheeraj Gupta dheeraj.gupta4 at gmail.com
Wed Sep 10 12:06:14 UTC 2014


Hi,
we are working on bug-1211011 (Flavors created in parent cell are not
propagated to the child cell)..
we need a few pointers from the community (and people working with cells).

The problem is that if the "instance_type" tables are not in sync in
all cells we can spawn a
different flavor than the one selected by the user.
Example: flavor_A is selected and in the child cell flavor_B is spawned.

This is because what is checked at spawn time is the
"instance_type_id" in the child cell database,
and there is not guarantee that this corresponds to the same flavor in
the parent cell.

A possible solution to this problem can be propagating the flavors to
all child cells when it is created/deleted/changed in the parent cell.
But since instance_type_id is an autoincrement field, it will be
difficult to sync it. Also there may be a problem when applying this
to an existing cell setup.

We believe that the flavors should only live in the parent cell (API cell).
In this case every time that this information is needed the child cell
needs to query the information
from the parents.

The problem is that at the moment in the child cells the compute api
not aware about cells.
Should this be reconsidered?

Also, having this mechanism to query the parent cell will allow to
more easily add support for security groups and aggregates.

Thoughts?

Regards,
Dheeraj



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