An example use case for make multi-threaded HTTP requests and using shared variables

print_gh_user_summaries.rb

require "json"
require "net/http"
require "ostruct"
require "amazing_print"

user_summaries = []
req_total_ms = 0

host = "api.github.com"

usernames = %w[
  dhh
  HarlemSquirrel
  jarednorman
  matz
  matzbot
  nateberkopec
  octocat
  tenderlove
]


Thread.abort_on_exception = true
semaphore = Thread::Mutex.new

puts "Getting #{usernames.size} user summaries..."
start_time = Time.now

threads = usernames.map do |username|
  Thread.new do
    Net::HTTP.start(host, use_ssl: true) do |http|
      path = "/users/#{username}"
      req_start_time = Time.now
      response = http.get(path)
      duration_ms = ((Time.now - req_start_time) * 1000).round(0)
      parsed_response_body = JSON.parse(response.body)
      user = OpenStruct.new(parsed_response_body)
      user_summary = {
        username: username,
        location: user.location,
        followers: user.followers,
        blog: user.blog,
        response_ms: duration_ms,
      }

      # Access shared variables
      semaphore.synchronize do
        user_summaries << user_summary
        req_total_ms += duration_ms
      end
    end
  end
end

threads.each(&:join)

real_time_ms = ((Time.now - start_time) * 1000).round(0)

puts user_summaries
puts "\nLoaded #{user_summaries.size} summaries in #{real_time_ms}ms"
puts "Total request time: #{req_total_ms}ms"