Cloned from launchpad blueprint https://blueprints.launchpad.net/nova/+spec/query-compute-node-conf-values.

Description:

At current migration of instances requires certain values to be consistent across all compute nodes (i.e. instance base, etc). 

We need to extend compute to provide a service to query these values as configured from remote nodes so that we may use them on the source and destination migration machines.  To do this we need to:

1) extend compute to respond to a config option query and pass back the data
2) add code to migrations to query the src/dst nodes for this data and use it during instance migration prep

This would also assist in migration cases where the glance image does not exist and we can use cached base image (qcow, ari, or aki) from the source node.

Specification URL (additional information):

None