This is potential break place once we have master that has lots of Gb's of data. We should not use RPC CALL method, because we can potentially fall into RPC Timeout.
As i can see we should do what we've did with backup API. We need to use RPC CAST and poll backup status(expecting two statuses: COMPLETED/FAILED), at taskmanager site, until it's ready. Another concern against RPC CALL: what if while we expecting for a response from guest AMPQ service will go down? How do we handle it? With give code - we're not doing anything (at the end we would have a backup record that hangs in NEW state).
RPC call timeout (higher one) is static per service launch (taskmanager).
So, there's no way to extend base timeout taking into account the size of master site's data.
See https://review.openstack.org/#/c/109687/11..12/trove/taskmanager/models.py,cm
