How to ensure consistency between redis and mysql

Methods to ensure consistency between Redis and MySQL include direct writing to MySQL and transaction compensation mechanisms: direct writing to MySQL: synchronizing MySQL data changes to Redis through triggers, ensuring consistency but lower performance; transaction compensation Mechanism: Write to Redis first, and record compensation transactions at the same time, tolerating short-term unavailability, but the consistency is slightly lower and the system complexity is higher.

How to ensure the consistency between Redis and MySQL

In system design, when using Redis as a cache, how to Ensuring data consistency with the back-end database MySQL is a common challenge. Two common methods are introduced below:

1. Write directly to MySQL

The most direct method is to write the data directly to MySQL and then synchronize the copy to Redis In cache. The advantage of this method is that data consistency is guaranteed, but it also brings performance losses.

2. Transaction compensation mechanism

Another method is to use the transaction compensation mechanism. When data is written to the Redis cache, a compensating transaction is recorded at the same time. If an error occurs while updating MySQL, a compensating transaction is triggered to roll back the data in the Redis cache.

The implementation, advantages and disadvantages of these two methods are introduced in detail below:

1. Directly write to MySQL

Implementation:

• In the application, write data directly to the MySQL database.
• Use triggers or other mechanisms to synchronize data changes in the MySQL database to the Redis cache.

Advantages:

• High data consistency because data is always written directly to MySQL.

Disadvantages:

• The performance overhead is large because each write operation involves two storage systems, MySQL and Redis.

2. Transaction compensation mechanism

Implementation:

• In the application, transfer the data Write to the Redis cache first.
• Also records a compensating transaction that updates data to the MySQL database.
• If the compensation transaction fails to execute, the compensation mechanism is triggered and the data in the Redis cache is rolled back.

Advantages:

• Performance is higher because writing to the Redis cache is asynchronous.
• Tolerate temporary unavailability of the MySQL database because compensating transactions can be executed later.

Disadvantages:

• Data consistency is not as good as writing directly to MySQL, because the data in Redis may be inconsistent with MySQL before the MySQL update is successful. .
• Needs to implement a compensation mechanism, which increases system complexity.

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