test ruby -> python interop via pipes

master.rb

require 'open3'
require 'json'
require 'pry'

module Interop
  def self.send json
    result, status = Open3.capture2("python slave.py",
                                    stdin_data: json)
    status.to_s # noop, get rid of unused variable warning
    JSON.parse(result)["return"]
  end
end

module Model
  def self.match query, num_results, min_score
    Interop.send JSON.generate({method: "match",
                                args: [query, num_results, min_score]
    })
  end
end

thread_pool = []

# simulate multiple users
10.times do |i|
  thread_pool << Thread.new do
    puts "Calling interop from thread #{i}"
    
    # Call python:
    # It looks like a regular method call!
    result = Model.match "i", i, 0
    
    puts "Got result back: #{result}"
  end
end
thread_pool.each {|t| t.join}

# open an interactive shell
binding.pry

slave.py

from json import loads, dumps
from sys import stdin, stdout

class Model:
    def match(self, query, n, min_score):
        return ["Mocked model.match called with:", query, n, min_score]

model_instance  = Model()

switcher = {
    "match": getattr(model_instance, "match")
}

caller_map      = loads(stdin.read())
method_desired  = caller_map["method"]
method_args     = caller_map["args"]

retval = switcher[method_desired](*method_args)
stdout.write(dumps({'return': retval}))
stdout.flush()