lookup returned nil.
Add a TODO to note where a future point of logging should occur once a
logger is present and a few additional comments to explain the program
flow.
Assuming the following output from a consul agent:
```
==> Consul agent running!
Version: 'v0.7.3-43-gc5e140c-dev (c5e140c+CHANGES)'
Node ID: '40e4a748-2192-161a-0510-9bf59fe950b5'
Node name: 'myhost'
```
it is now possible to lookup nodes by their Node Name or Node ID, or a
prefix match of the Node ID, with the following caveats re: the prefix
match:
1) first eight digits of the Node ID are a required minimum (eight was
chosen as an arbitrary number)
2) the length of the Node ID must be an even number or no result will be
returned.
```
% dig @127.0.0.1 -p 8600 myhost.node.dc1.consul.
myhost.node.dc1.consul. 0 IN A 127.0.0.1
% dig @127.0.0.1 -p 8600 40e4a748-2192-161a-0510-9bf59fe950b5.node.dc1.consul.
40e4a748-2192-161a-0510-9bf59fe950b5.node.dc1.consul. 0 IN A 127.0.0.1
% dig @127.0.0.1 -p 8600 40e4a748.node.dc1.consul.
40e4a748.node.dc1.consul. 0 IN A 127.0.0.1
% dig @127.0.0.1 -p 8600 40e4a74821.node.dc1.consul.
40e4a74821.node.dc1.consul. 0 IN A 127.0.0.1
% dig @127.0.0.1 -p 8600 40e4a748-21.node.dc1.consul.
40e4a748-21.node.dc1.consul. 0 IN A 127.0.0.1
```
Previously the blocking functions all closed over the state store from
their first query, with would not have worked properly when a restore
occurred. This makes sure they get a frest state store pointer each time,
and that pointer is synchronized with the abandon watch.
We always did an update before which caused excessive watch churn, even
with our new fine-grained queries. This does a diff any only updates the
node and service records if something actually changed.
We can't actually return a fine-grained index from these tables unless
support is added for tombstones. Otherwise, the index could slip backwards
as things are deleted.
This fixes#2663 and fixes#1899. It's not super related to this PR,
but the startup time changes that this PR brings made this a lot worse
so I was able to track it down.
