Adding support for Consul tests

[armon]

This is probably a very newb PR so please forgive. I've cargo-culted most of this to make it work based on the etcd work. The one thing is it seems Jepsen does value based CAS while Consul does index based CAS. I've worked around to first do a read to get the index and then do the CAS operation. Not sure if there is a way to improve this by passing the index from a read into the CAS operation. Thanks!

[jpfuentes2]

I was still looking to clean this up if you're interested. One of the things I wanted to remove was the etcd workarounds that accounts for the startup failure bug. Also, I'm looking to finish up a Clojure-consul client soon enough.

I think we can handle the index-based CAS by passing it to the op since it's just a hash-map:

Roughly:

:read  (try (let [response (consul-get client)
                  value (parse-value response)
                  idx (parse-index response)]
              (assoc op :type :ok :value value :index idx))

:cas   (try
           (let [[value value'] (:value op)
                 ok?            (consul-cas client
                                            (:index op)
                                            (json/generate-string value)
                                            (json/generate-string value'))]

[aphyr]

Sorry for the delay; came into work and found a fire. Lemme see.

[aphyr]

If you have init scripts for Consul, it might be more concise to install and call them using service consul start.

[armon]

@aphyr Thanks for the feedback. Been a long day, will try to cleanup the PR tomorrow and work with @jpfuentes2 on it.

[jpfuentes2]

Okay, I made a lot of changes to clean up some of the cruft and copy-pasta from the etcd example. Also improved the style to be a better Clojure citizen.

I welcome further review whenever you have a chance. Thanks!

[aphyr]

Teardown actually gets called for you prior to setup!, so you can elide this too. :)

[jpfuentes2]

Thanks, I see that now:

(defn cycle!
  "Tries to tear down, then set up, the given DB."
  [db test node]
  (try (teardown! db test node)
       (catch RuntimeException _))
  (setup! db test node))

[aphyr]

OK, all this looks generally good to me! Sorry about the insane wait, I'm whittling down the PR backlog this month. :)

[jpfuentes2]

Sounds good to me. Do you want me to try my hand at resolving merge conflicts?

[aphyr]

Got it merged, porting your stuff forward to the new code structure now.

[aphyr]

OK, so I hooked up the dependency machinery and all; you can run the tests with lein with-profile +consul test jepsen.system.consul-test, but they crash with /var/log/consul.log: Permission denied; probably just an issue in the setup permissions but I'm not gonna dig into it too deep right now.