rinterface: Ruby to Erlang client

rinterface is a pure Ruby client that can send RPC calls to an Erlang node. It’s very much a work in progress.

Requirements

• Erlang 12B-5
• Ruby
• Ruby gems
• Eventmachine

Try it out

1. Open a terminal, Cd into the test directory and run: ‘make’ ‘make run’

This will start the erlang node named ‘math’

2. Open another terminal, and run: ‘ruby sample.rb’

How to use?

In your Ruby code, make a call to the Erlang node like this:

Erlang::Node(nodename,module,function,args) => [:ok,Response] | [:badprc,Reason]

  r = Erlang::Node.rpc("math","math_server","add",[10,20])

 if r[0] == :badrpc
   puts "Got and Error. Reason #{r[1]}"
 else
   puts "Success: #{r[1]}"
 end

Where:

• math is the node name (the -sname of the Erlang node)
• math_server is the name of the module
• add is the funtion to call
• [10,20] is an array of arguments to pass to the function

The result will always be an Array of the form:

 [:ok,Response] where Response is the result from the Erlang

or
[:badrpc,Reason] where Reason is the ‘why’ it failed

So you wanna call Erlang from your Rails app…

Here’s a quick and simple example. Make sure you put the rinterface lib into RAILS_ROOT/lib and start the math_server in ‘test’

In the controller:

controllers/math_controller.rb

require "lib/rinterface"

class MathController < ApplicationController
  def index
    a = params[:a]
    b = params[:b]
    r = Erlang::Node.rpc("math","math_server","add",[a.to_i,b.to_i])
    
    if r[0] == :badrpc
      @result = "Error"
    else
      @result = r[1]
    end
    
  end
end

Finally, add a template for the view, and try ‘http://localhost:3000/math?a=2&b=3’.

This is not ideal yet and not something I’d use yet in production, but it’s a starting point for experimenting.