The magical combination of MULTI and EXEC in Redis transactions

Table of contents

introduction

A brief introduction to Redis transactions

MULTI: Open the door to business

EXEC: the time when the transaction is committed

DISCARD: The savior of canceling transactions

Best practice: combined application of MULTI and EXEC

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introduction

In Redis, transactions are a powerful and flexible feature that provides developers with a mechanism to package multiple commands and execute them atomically. The core commands MULTI and EXEC and the auxiliary commands DISCARD together form the basis of Redis transactions.

A brief introduction to Redis transactions

Redis transactions allow developers to package a series of Redis commands into an atomic operation unit, ensuring that these commands either all execute successfully or all fail. This feature of atomic execution is particularly important in distributed systems to ensure data consistency and reliability.

MULTI: Open the door to business

MULTI is the entry command of Redis transaction, and its function is to start a transaction. Once the MULTI command is called, all subsequent Redis commands will be put into a transaction queue, but will not be executed immediately. This provides developers with an opportunity to package multiple commands, ensuring that they are executed atomically.

MULTI
SET key1 value1
SET key2 value2

In the above example, two commands, SET key1 value1 and SET key2 value2, are placed in the transaction queue.

EXEC: the time when the transaction is committed

EXEC is the key command in the Redis transaction. Its function is to execute all commands in the transaction queue and submit them to the Redis server as an atomic operation. Once EXEC is called, Redis will execute the commands in sequence in the transaction queue.

MULTI
SET key1 value1
SET key2 value2
EXEC

In the above example, the two commands SET key1 value1 and SET key2 value2 will not be actually executed until EXEC is called. If an error occurs during transaction execution, the entire transaction is rolled back to maintain data consistency.

DISCARD: The savior of canceling transactions

DISCARD is the savior of Redis transactions. Its function is to cancel the transaction and abandon all enqueued commands. is an effective method when there is a problem with the commands in the transaction or when the transaction needs to be canceled between the execution of MULTI and EXEC means. DISCARD

MULTI
SET key1 value1
SET key2 value2
DISCARD

In the above example, the two commands SET key1 value1 and SET key2 value2 will be cleared when DISCARD is called, and the entire The transaction was cancelled.

Best practice: combined application of MULTI and EXEC

Jedis jedis = new Jedis("localhost", 6379);
Transaction transaction = jedis.multi();

try {
    // 事务中的命令
    transaction.set("key1", "value1");
    transaction.set("key2", "value2");
    
    // 提交事务
    List<Object> result = transaction.exec();
    
    // 处理事务执行结果
    if (result == null) {
        // 事务执行失败，执行回滚或其他操作
        transaction.discard();
    } else {
        // 事务执行成功，继续其他业务逻辑
    }
} catch (Exception e) {
    // 处理异常，执行回滚或其他操作
    transaction.discard();
} finally {
    jedis.close();
}

In Java, more complex transaction operations can be implemented through the combination of MULTI and EXEC and the exception handling mechanism. Each command in the transaction will be executed atomically to ensure data consistency and reliability.