redis counts

run.rb

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'redis'
  gem "hiredis-client" 
  # gem 'rspec'
end

require "hiredis-client" # speed optimized redis client
require 'date'

# CONSTANTS

NUM_VIEWS = 10
PROPERTY_IDS = [42, 43]
DAYS_TRACKED = 2
SECONDS_IN_A_DAY = 24 * 60 * 60

# METHODS

def cache_key(property_id, date)
  "properties:views:#{property_id}:#{date}"
end

def set_key_expiry(redis, key, date)
  expiry_date_timestamp = date + (DAYS_TRACKED * SECONDS_IN_A_DAY) + 1
  redis.expireat(key, expiry_date_timestamp)
end

def track_property_view(redis, property_id, date)
  # generate the cache key
  key = cache_key(property_id, date)

  # always increment
  view_count = redis.incr(key)

  # if view_count is 1, this is a new key. then also set expiry
  set_key_expiry(redis, key, date) if view_count == 1

  # puts "#{key}: #{view_count} views, expires at: #{Time.at(redis.expiretime(key))}"
end

def get_property_views(redis, property_id, date_keys)
  keys = date_keys.map { |date| cache_key(property_id, date) }
  redis.mget(*keys).sum(&:to_i)
end

# START CODE

redis = Redis.new  
redis.flushall

# generate an array of unix timestamps for the last DAYS_TRACKED days

date_keys = ((Date.today - DAYS_TRACKED + 1)..Date.today).map { |date| date.to_time.utc.to_i }

# generate some fake property views (sample data)

NUM_VIEWS.times do |i|
  property_id = PROPERTY_IDS.sample
  date = date_keys.sample
  track_property_view(redis, property_id, date)
end

# show views

PROPERTY_IDS.each do |property_id|
  views_count = get_property_views(redis, property_id, date_keys)
  puts "Property #{property_id}: #{views_count} views in the last #{DAYS_TRACKED} days"
end