BIGTOP-2476 Add Zookeeper Charm

[petevg]

Based on the vanilla apache-zookeeper charm, but utlizes Bigtop to
reduce complexity in the charm itself.

@juju-solutions/bigdata: Since I'm still a newb, I'm pushing one more PR w/ the team before submitting upstream. This, I think, is the final, actually working, following all the best practices version of this charm. If you agree, please +1. If I missed something, please let me know, and I'll fix it :-)

[kwmonroe]

I have a couple issues with the status reporting

• First, please make all status_set messages lowercase. hookenv.log is fine to have proper sentences with capitalization, but we want all our status_set messages to be lower.
• Second, I thought the old charm's reporting of suboptimal (non-quorum) status was useful. Please consider adding this functionality back. The old was of doing it was a very simple grep of zoo.cfg:

https://github.com/juju-solutions/layer-apache-zookeeper/blob/master/lib/charms/layer/zookeeper.py#L183

Followed by setting the appropriate message if we had a suboptimal quantity of peers:

https://github.com/juju-solutions/layer-apache-zookeeper/blob/master/reactive/zookeeper.py#L44

If you brought this back, you could add a reactive handler like this:

@when('zookeeper.started')
def update_status():
    num = <num_peers>
    if num is good:
        status_set('active', 'ready')
    else:
        status_set('active', 'suboptimal number of peers (num)')

[petevg]

Fixed the status messages.

I think that, with the messaging complexity we've introduced by not doing automatic restarts, I'd rather skip the notifications about inadequate numbers for quorum for now.

When we add the automated restarts back in, though, I like the idea of adding those messages back in as well.

[petevg]

@kwmonroe I lied about the messing being too complex. Functionality from the old charm ported over. :-)

[kwmonroe]

lc ftw

[johnsca]

Also, it should be maintenance instead of waiting.

[kwmonroe]

lc ftw

[kwmonroe]

lc ftw

[johnsca]

This should be predicated on the zookeeper.started state and should action_fail if it's not set.

[petevg]

@johnsca Done.

[kwmonroe]

there is no smoke-test action in this charm.. this isn't necessarily a bad thing since it will just pick up the default smoke-test from here:

https://github.com/juju-solutions/layer-apache-bigtop-base/blob/master/actions/smoke-test

just wanted to make sure you knew this would happen, and that there was no custom smoke-test handling required for zk.

[petevg]

@kwmonroe Yep. The default smoke test action is just fine for Zookeeper -- we don't need to do any special setup.

[petevg]

I've opened a PR upstream, so closing out this PR.