threads

non_threadsafe.rb

require 'open-uri'

def link_valid?(url)
  open(url)
  true
rescue
  false
end

def validate_urls(urls)
  urls = urls.dup

  threads = 3.times.map do |url_subset|
    Thread.new do
      while !urls.empty?
        url = urls.pop
        yield url, link_valid?(url)
      end
    end
  end

  p threads.map(&:join)
end

urls = %w(
  http://rubysource.com
  http://xaviershay.com
  http://twitter.com
  not_a_link
  http://bogus.bogus
)

validate_urls(urls) do |url, valid|
  puts "#{url} was #{valid ? "valid" : "invalid"}"
end

queue_threadsafe.rb

require 'thread'

queue = Queue.new
# with an array, this will give some problems
# queue = []

producer = Thread.new do
  5.times do |i|
    sleep rand(i) # simulate expense
    queue << i
    puts "#{i} produced"
  end
end

consumer = Thread.new do
  5.times do |i|
    value = queue.pop
    sleep rand(i/2) # simulate expense
    puts "consumed #{value}"
  end
end

consumer.join

simple_thread.rb

require 'open-uri'

def link_valid?(url)
  open(url)
  true
rescue
  false
end

def validate_urls(urls)
  number_of_threads = (urls.length / 3.0).round # 3 threads

  puts "Creating #{number_of_threads} threads"

  threads = urls.each_slice(number_of_threads).map do |url_subset|
    Thread.new do
      url_subset.each do |url|
        yield url, link_valid?(url)
      end
    end
  end

  p threads.map(&:join)
end

urls = %w(
  http://rubysource.com
  http://xaviershay.com
  http://twitter.com
  not_a_link
  http://bogus.bogus
)

validate_urls(urls) do |url, valid|
  puts "#{url} was #{valid ? "valid" : "invalid"}"
end

urls_threadsafe.rb

require 'open-uri'
require 'thread'

def link_valid?(url)
  open(url)
  true
rescue
  false
end

def validate_urls(urls)
  queue = Queue.new
  urls.each { |u| queue << u }

  threads = 5.times.map do
    Thread.new do
      while !queue.empty?
        url = queue.pop
        yield url, link_valid?(url)
      end
    end
  end

  p threads.map(&:join)
end

urls = %w(
  http://rubysource.com
  http://xaviershay.com
  http://twitter.com
  not_a_link
  http://bogus.bogus
)

validate_urls(urls) do |url, valid|
  puts "#{url} was #{valid ? "valid" : "invalid"}"
end

urls_threadsafe_and_sync.rb

require 'open-uri'
require 'thread'

def link_valid?(url)
  open(url)
  true
rescue
  false
end

def validate_urls(urls)
  queue = Queue.new
  semaphore = Mutex.new
  urls.each { |u| queue << u }

  threads = 5.times.map do
    Thread.new do
      while !queue.empty?
        url = queue.pop
        valid = link_valid?(url)

        semaphore.synchronize {
          yield url, valid
        }
      end
    end
  end

  p threads.map(&:join)
end

urls = %w(
  http://rubysource.com
  http://xaviershay.com
  http://twitter.com
  not_a_link
  http://bogus.bogus
)

validate_urls(urls) do |url, valid|
  puts "#{url} was #{valid ? "valid" : "invalid"}"
end