Redis lock implementation principle

Redis lock is a distributed lock mechanism, implemented through the following steps: 1. Acquire lock (SETNX); 2. Release lock (DEL); 3. Set expiration time (EXPIRE); 4. Lock competition . Its advantages are distributed, simple, efficient, and scalable, but it has limitations such as deadlock, unguaranteed order, and the need to set expiration times.

Redis lock implementation principle

Redis lock is a distributed lock mechanism implemented using Redis. Solve resource competition problems caused by concurrent access. It is mainly implemented through the following steps:

1. Obtain the lock

• The client sends the SETNX command to the Redis server, trying to set the specified The value of key is set to 1 (representing acquiring the lock).
• If the key does not exist or the value is 0, Redis will set the value of the key to 1 and return 1 (successfully acquiring the lock).
• Otherwise, return 0 (the lock has been acquired by other clients).

2. Release the lock

• The client sends the DEL command to the Redis server to delete the specified key.
• If the key exists and the value is equal to 1, Redis will successfully delete the key (release the lock).
• Otherwise, return 0 (the lock release failed, possibly because the lock has been preempted by other clients or has expired).

3. Set expiration time

• To avoid deadlock, the client usually sets an expiration time for the lock (EXPIREOrder).
• During the expiration period, other clients cannot obtain the lock.
• After the expiration time, the lock is automatically released.

4. Lock competition

• If multiple clients try to acquire the same lock at the same time, only one client can succeed.
• Other clients will retry continuously until the lock is successfully acquired or the lock expires.

Advantages:

• Distributed: Based on Redis implementation, lock acquisition can be coordinated across multiple servers.
• Easy to use: The SETNX and DEL commands are easy to understand and use.
• Efficient: Redis's high performance ensures fast lock acquisition and release.
• Scalable: Redis's cluster architecture allows the lock function to be expanded to meet high concurrency needs.

Limitations:

• Possible deadlock: if the client crashes before releasing the lock, the lock may not be released.
• The order of locks cannot be guaranteed: multiple clients may try to acquire locks at the same time, and the order in which the locks are ultimately acquired cannot be guaranteed.
• The expiration time needs to be set: The expiration time must be set to avoid deadlock, but setting the expiration time too short may lead to frequent lock competition, and setting the expiration time too long may lead to a waste of resources.

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