Implement configuration attach and detach API for clusters.
Implement rolling strategy for applying configuration changes
(both attach and detach follow the same pattern).
1. Persist the changes on all nodes (leaving nodes in RESTART_REQUIRED state).
2. Update Trove records.
3. Apply changes dynamically via one or all node(s) if possible
(and remove RESTART_REQUIRED flag from all nodes).
Notes:
The single instance implementation has been restructured (similar to above)
such that it always leaves the instance in one of the three states:
a) Unchanged
b) Changes persisted but not applied
(Instance has configuration attached but requires restart.
It is safe restart manually or detach the group to avoid
any changes)
c) Changes persisted and applied (if possible)
This implemenation should always leave the cluster (and each instance)
in a consistent state.
Runtime configuration will not be changed until it is first persisted
on all nodes.
If there is a failure during step 1) the cluster is still running
the old configuration. Some instances may have new configuration
persisted, but not applied.
The cluster will not have configuration attached unless it can
be applied to all nodes.
The individual nodes will have configuration attached as soon as it is
persisted on the guest.
It is safe to retry, reapplying the same configuration on a node is
noop.
It is safe to detach. Removing configuration from nodes without one
is a noop.
It is safe to detach the configuration from individual nodes via
single-instance API.
It is safe to attach the configuration to remaining nodes via
single-instance API and rerun cluster attach to update Trove records.
If 3) fails for whatewer reason the instances are left
in RESTART_REQUIRED state.
It is safe to retry or detach configuration or restart the
instances manually.
Also fixed various minor cluster issues.
Implements: blueprint cluster-configuration-groups
Change-Id: I7c0a22c6a0287128d0c37e100589c78173fd9c1a
9bca402ec3