charm needs to implement required_relations (block until control plane is ready)

[Ryan Beisner]

Per policies and best practices, the charm should deploy to a non-error state (blocked is ok). However, when deployed without config, or before the remote compute host is ready, the install proxy charm hook fails.

We should check that the remote host is up before firing the proxy installation, and block until it is reachable.

We should also implement require_relations and block until that is satisfied.

Logs and artifacts:

https://openstack-ci-reports.ubuntu.com/artifacts/test_charm_pipeline/openstack/charm-nova-compute-proxy/393024/2/1119/index.html

[Ryan Beisner (1chb1n)]

This issue affects usability of the charm in production and testing as well. If a bundle is deployed, the nova-compute-proxy proxy_install routines will most likely try to execute long before glance and other relations are ready.

[Ryan Beisner (1chb1n)]

Specifically, instantiation of a REMOTEProxy object should not raise an exception when configs are missing.

unit-nova-compute-proxy-0[2569]: 2016-11-03 16:33:24 INFO unit.nova-compute-proxy/0.juju-log server.go:268 Registered config file: /var/lib/charm/nova-compute-proxy/etc/nova/nova.conf
unit-nova-compute-proxy-0[2569]: 2016-11-03 16:33:24 INFO unit.nova-compute-proxy/0.config-changed logger.go:40 Traceback (most recent call last):
unit-nova-compute-proxy-0[2569]: 2016-11-03 16:33:24 INFO unit.nova-compute-proxy/0.config-changed logger.go:40 File "/var/lib/juju/agents/unit-nova-compute-proxy-0/charm/hooks/config-changed", line 48, in <module>
unit-nova-compute-proxy-0[2569]: 2016-11-03 16:33:24 INFO unit.nova-compute-proxy/0.config-changed logger.go:40 password=config('remote-password'))
unit-nova-compute-proxy-0[2569]: 2016-11-03 16:33:24 INFO unit.nova-compute-proxy/0.config-changed logger.go:40 File "/var/lib/juju/agents/unit-nova-compute-proxy-0/charm/hooks/nova_compute_proxy.py", line 75, in __init__
unit-nova-compute-proxy-0[2569]: 2016-11-03 16:33:24 INFO unit.nova-compute-proxy/0.config-changed logger.go:40 raise Exception('Missing configuration')
unit-nova-compute-proxy-0[2569]: 2016-11-03 16:33:24 INFO unit.nova-compute-proxy/0.config-changed logger.go:40 Exception: Missing configuration
unit-nova-compute-proxy-0[2569]: 2016-11-03 16:33:24 ERROR juju.worker.uniter.operation runhook.go:107 hook "config-changed" failed: exit status 1