Concurrent-Ruby Promises Example

concurrent_ruby_test.rb

require "bundler/inline"

# https://ruby-concurrency.github.io/concurrent-ruby/1.1.4/Concurrent/Promise.html

gemfile do
  source "https://rubygems.org"
  gem "concurrent-ruby"
  gem "http"
  gem "logger"
  gem "pry"
end

URL = "http://slowwly.robertomurray.co.uk/delay/3000/url/http://www.google.com".freeze
LOGGER = Logger.new("./concurrent_test.log")
EXECUTOR = Concurrent::FixedThreadPool.new(5)

def external_calls(counter, executor, logger)
  Concurrent::Promise.new(executor: executor) { HTTP.get(URL) }
                     .then { HTTP.get(URL) }
                     .then { HTTP.get(URL) }
                     .then { |response| logger.info "#{counter}: #{response.code}" }
                     .on_error { |e| logger.error "#{counter}: #{e}" }
                     .execute
end

(0..5).map { |i| external_calls(i, EXECUTOR, LOGGER) }.each(&:wait)