似乎無法保持redis計數器正確

Question

我有幾個計數器存儲在REDIS中，這些計數器在customer.rb中的狀態更改時得到更新。我需要存儲的事情是：

1）與用戶相關聯的客戶的計數（用戶的has_many客戶） 2）具有（使用aasm_state）「開」或「權利」 3的狀態的客戶計）具有（使用aasm_state）狀態的客戶數「打開

每當客戶狀態發生變化時，我相應地增加/減少redis計數器。但是，無論我嘗試過什麼，計數似乎總是在一定時間後關閉。

我正在使用Sidekiq，但我不認爲這是一個併發問題，因爲REDIS不應該受到併發問題，對吧？

這裏是我的計數方法更新：

def reset_stats 
    if aasm_state_was == 'open' && aasm_state == 'claimed' # open => assigned 
     # update company and user 
     user.redis_increment_my_customers_length 
     company.redis_decrement_open_customers_length 

    elsif user_id_changed? && aasm_state_was == 'claimed' && aasm_state == 'claimed' # assigned => assigned 
     # update users (assigner and assignee) 
     user_was = User.find(user_id_was) 
     user.redis_increment_my_customers_length 
     user_was.redis_decrement_my_customers_length 

    elsif aasm_state_was == 'claimed' && aasm_state == 'closed' # assigned => closed 
     # update company and user 
     user_was = User.find(user_id_was) 
     user_was.redis_decrement_my_customers_length 
     company.redis_decrement_all_customers_length 

    elsif aasm_state_was == 'closed' && aasm_state == 'claimed' # closed => assigned 
     # update company and user 
     user.redis_increment_my_customers_length 
     company.redis_increment_all_customers_length 

    elsif aasm_state_was == 'closed' && aasm_state == 'open' # closed => open 
     # update company 
     company.redis_increment_all_customers_length 
     company.redis_increment_open_customers_length 

    elsif aasm_state_was == 'open' && aasm_state == 'closed' # open => closed 
     # update company 
     company.redis_decrement_all_customers_length 
     company.redis_decrement_open_customers_length 

    end 

和user.rb：

def redis_length_key 
    "my_customers_length_for_#{id}" 
    end 

    def set_my_customers_length(l) 
    RED.set(redis_length_key, l) 
    l.to_i 
    end 

    def redis_increment_my_customers_length 
    RED.get(redis_length_key) ? RED.incr(redis_length_key) : my_customers_length 
    end 

    def redis_decrement_my_customers_length 
    RED.get(redis_length_key) ? RED.decr(redis_length_key) : my_customers_length 
    end 

    def my_customers_length 
    if l = RED.get(redis_length_key) 
     l.to_i 
    else 
     set_my_customers_length(my_customers.length) 
    end 
    end 

和company.rb：

def open_customers 
    customers.open 
    end 

    def redis_open_length_key 
    "open_customers_length_for_#{id}" 
    end 

    def set_open_customers_length(l) 
    RED.set(redis_open_length_key, l) 
    l.to_i 
    end 

    def redis_increment_open_customers_length 
    RED.get(redis_open_length_key) ? RED.incr(redis_open_length_key) : open_customers_length 
    end 

    def redis_decrement_open_customers_length 
    RED.get(redis_open_length_key) ? RED.decr(redis_open_length_key) : open_customers_length 
    end 

    def open_customers_length 
    if l = RED.get(redis_open_length_key) 
     return l.to_i 
    else 
     set_open_customers_length(open_customers.length) 
    end 
    end 

    def redis_all_length_key 
    "all_customers_length_for_#{id}" 
    end 

    def set_all_customers_length(l) 
    RED.set(redis_all_length_key, l) 
    l 
    end 

    def redis_increment_all_customers_length 
    RED.get(redis_all_length_key) ? RED.incr(redis_all_length_key) : all_customers_length 
    end 

    def redis_decrement_all_customers_length 
    RED.get(redis_all_length_key) ? RED.decr(redis_all_length_key) : all_customers_length 
    end 

    def all_customers_length 
    if l = RED.get(redis_all_length_key) 
     l.to_i 
    else 
     set_all_customers_length(open_or_claimed_customers.length) 
    end 
    end 

    def open_or_claimed_customers 
    customers.open_or_claimed 
    end 

有沒有更好的模式什麼我正在努力完成？這一直非常令人沮喪，因爲這些計數在一段時間後似乎總是不正確。請幫忙！

Answer 1

在您撥打電話號碼set_my_customers_length(my_customers_length + 1)和撥打電話RED.set(redis_open_length_key, l)之間的時間段內，您會遇到競爭狀況。

1. 兩個過程開始。
2. my_customers_length在第一次調用這兩個進程時爲5。
3. 第一個進程進行第二次調用，並將Redis設置爲6.
4. 第二個進程進行第二次調用，並將Redis再次設置爲6。
5. Redis的價值其實應該是7

考慮使用Redis的INCR與DECR功能原子更新值。

• http://redis.io/commands/incr
• http://redis.io/commands/decr
• http://redis.io/commands/incrby
• http://redis.io/commands/decrby

Answer 2

你有一個競爭條件在這裏：

RED.get(redis_all_length_key) ? RED.incr(redis_all_length_key) : all_customers_length 

你不能做任何邏輯類型B在閱讀和寫信給Redis之前。