A ridiculous Halloween-themed example of stats tracking using Redis bitwise operations

trickortreat.rb

require 'redis'

class TrickOrTreatTracker
  def initialize
    @redis = Redis.new
  end

  def track_trick(user_id)
    key = "trick-#{Time.now.hour}"
    @redis.setbit key, user_id, 1
    @redis.sadd "trick", key
  end

  def track_treat(user_id)
    key = "treat-#{Time.now.hour}"
    @redis.setbit key, user_id, 1
    @redis.sadd "treat", key
  end

  def unique_tricks(hour=nil)
    do_unique(:trick, hour)
  end

  def unique_treats(hour=nil)
    do_unique(:treat, hour)
  end

  def unique_tricks_and_treats(hour=nil)
    do_unique(:trick, hour) + do_unique(:treat, hour)
  end

  def check_user(user_id, hour=nil)
    tricked = false
    treated = false
    if hour.nil?
      tricked = @redis.smembers("trick").any? do |key|
        @redis.getbit(key, user_id) == 1
      end
      treated = @redis.smembers("treat").any? do |key|
        @redis.getbit(key, user_id) == 1
      end
    else
      tricked = (@redis.getbit("#{trick}-#{hour}", user_id) == 1)
      treated = (@redis.getbit("#{treat}-#{hour}", user_id) == 1)
    end
    puts "user #{user_id}: hour=#{hour.nil? ? 'all' : hour} tricked=#{tricked}, treated=#{treated}"
  end

  private

  def do_unique(type, hour)
    # if hour is nil, then do all tricks/treats
    if hour.nil?
      @redis.smembers("#{type}").inject(0) do |total, key|
        total + @redis.bitcount(key)
      end
    else
      @redis.bitcount "#{type}-#{hour}"
    end
  end
end

if __FILE__ == $0
  Redis.new.flushall

  tracker = TrickOrTreatTracker.new

  rand(10).times do
    tracker.track_trick(rand(20))
  end

  rand(10).times do
    tracker.track_treat(rand(20))
  end

  puts "Total Unique Tricks: #{tracker.unique_tricks}"
  puts "Total Unique Treats: #{tracker.unique_treats}"
  puts "Combined Unique Tricks/Treats: #{tracker.unique_tricks_and_treats}"
  (0...20).each do |user_id|
    tracker.check_user user_id
  end
end