who_is_online

# Defining the keys
 
def current_key
  key(Time.now.strftime("%M"))
end
 
def keys_in_last_5_minutes
  now = Time.now
  times = (0..5).collect {|n| now - n.minutes }
  times.collect{ |t| key(t.strftime("%M")) }
end
 
def key(minute)
  "online_users_minute_#{minute}"
end
 
# Tracking an Active User
 
def track_user_id(id)
  key = current_key
  redis.sadd(key, id)
end
 
# Who's online
 
def online_user_ids
  redis.sunion(*keys_in_last_5_minutes)
end
 
def online_friend_ids(interested_user_id)
  redis.sunionstore("online_users", *keys_in_last_5_minutes)
  redis.sinter("online_users", "user:#{interested_user_id}:friend_ids")
end