Add health check command

[dmah42]

Part of #42

This also introduces a gRPC client with an implementation for the Discovery service that can be copied for Runtime services later.

NOTE: this assumes all instances of auraed are listening on the same port, which is not guaranteed.. more flexibility can be added.

to test

• run auraed: sudo -E auraed --socket "0.0.0.0:8080"
• run ae: ae health --cidr <local network cidr: 192.168.0.0/24> --port 8080

experience output :)

[krisnova]

Can we have cidr as the 3rd subcommand?

ae health cidr <cidr range>
ae health cidr 10.0.0.1/24

ae health <host>
ae health nivenly.biz
ae health 10.0.0.17

The reason I say this is because I believe we are going to need to start moving our clustering/networking paradigms into common libraries. If it is a 3rd subcommand this allows us to add others in the future such as

ae health cluster <primary-node>
ae health hostpattern <DNS regular expression>
ae health arp // everyone in the arp tables
ae health route // everyone in the route tables

I believe that the scheduler core libraries will likely end up starting/living here in the ae repository. Which means we will likely need some libraries that enable behavior such as:

worker := func() error { return nil } // TODO add work here
sched := scheduler.CIDRIterator()
sched.Work(worker)
err := sched.Run()

such that we can easily perform tasks at scale.

I suspect we will have many scheduler/iterators/walkers as we grow. For example I could also see something like

worker := func() error { return nil } // TODO add work here
sched := scheduler.ClusterWalker("hachyderm.io")
sched.Work(worker)
err := sched.Run()

Then we can just have an interface for all of our valid worker commands, and health is just yet-another-worker implementation that can be passed to any scheduler/iterator/walker.

[dmah42]

i'm iterating on this.

[dmah42]

./bin/ae health cidr 192.168.178.85/29 --port 8080

[dmah42]

./bin/ae health ip 192.168.172.86 --port 8080 also works, as does ./bin/ae health ip 2a02:8012:b1c:0:6ff3:68fd:38e8:396f --port 8080

[krisnova]

Great job pulling things out into /health