The principle of redis lock

Redis lock is a lightweight locking mechanism based on the SETNX principle, used to coordinate access to shared resources. Its working principle includes: setting lock, setting expiration time, checking lock holder, and releasing lock. Advantages include lightweight, high performance, and protection against deadlocks, disadvantages include only working with Redis-managed resources and possible lock contention.

The principle of Redis lock

Redis lock is a lightweight locking mechanism used to coordinate access to shared resources. It is implemented based on the atomicity and single-threaded execution model of Redis.

Detailed explanation of the principle

The principle of Redis lock is based on the SETNX (SET if Not eXists) command. When a client attempts to acquire a lock, it uses SETNX to set a value for a specific key. If the key does not exist, SETNX succeeds and returns 1, indicating that the lock was acquired. If the key already exists, SETNX fails and returns 0, indicating that the lock is already held by another client.

In order to prevent deadlock, the lock usually sets an expiration time. When the lock holder releases the lock, it uses the DEL command to delete the key. If the lock is not released within the expiration time, Redis will automatically delete the key and release the lock.

Steps to acquire a lock

1. Attempt to acquire a lock: Use SETNX to set a value for a unique key.
2. Set expiration time: Use the EXPIRE command to set an expiration time for the lock.
3. Acquiring the lock successfully: If SETNX returns 1, it means the lock has been acquired successfully.
4. Failed to acquire the lock: If SETNX returns 0, it means that the lock is already held by another client.

Steps to release the lock

1. Check the holder of the lock:Use the GET command to obtain the current value of the lock.
2. Determine whether to release the lock: If the obtained value is consistent with the value currently held by the client, release the lock.
3. Release the lock: Use the DEL command to delete the key of the lock.

Advantages and Disadvantages

Advantages:

• Lightweight and high-performance
• Cross-process coordination Resource access
• Prevent deadlock

Disadvantages:

• Only applicable to resources managed by Redis
• There may be lock contention, causing performance issues

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