This is an small Erlang application demostrating some of the features of Erlang/OTP.

I commented the core modules heavily. So hopefully they can be read by those having no prior exposure to Erlang whatsoever.

The recommended order is below:

1. src/coordinator.erl

   Implements the coordinator behavior that accepts abstract CPU-intensive jobs, deduplicates them when possible, computes job results limiting maximum parallelism.

2. src/demo_worker.erl

   Instantiates the coordinator behavior telling it how to compute Fibonacci numbers (in a way that is deliberately very slow).

   An instance of this process will be running on each Erlang node.

3. src/demo.erl

   A wrapper module that distributes jobs to demo_worker processes an connected nodes using consistent hashing.

4. src/demo_rest.erl

   Optional (as I didn't leave any comments here). This module exposes the APIs exposed by demo via HTTP.

$ rebar3 compile
$ rebar3 release

$ ./start.sh --node [email protected] --cookie secret --port 8080

$ ./start.sh --node [email protected] --cookie secret --bootstrap [email protected] --port 8081

$ curl -s -XGET http://127.0.0.1:8080/stats | jq .
{
  "[email protected]": {
    "ok": 129,
    "failed": 0,
    "computed_ok": 88,
    "computed_failed": 0,
    "accepted": 135
  }
}

$ curl -s -XDELETE http://127.0.0.1:8080/stats | jq .
"ok"

$ curl -s -XGET http://127.0.0.1:8080/fibonacci/42 | jq .
{
  "result": 433494437,
  "n": 42
}