Java Distributed Locks Explained

The working principle of Java distributed locks mainly includes the following steps:

1. Obtaining a lock: When a thread needs to acquire a distributed lock, it first sends a request to the distributed lock service to obtain the lock.
2. The lock service processes requests by first checking if the lock has already been taken by another thread.
3. The lock is available: If the lock is not in use, it will be set to occupied and the current thread will become the holder of the lock. The request to acquire the lock will be successful.
4. The lock is unavailable: if the lock is already being held by another thread, the lock service will add the request for obtaining the lock to a waiting queue and wait for the lock to be released.
5. Waiting for lock release: Requests in the waiting queue will be awakened according to a certain strategy once the lock holder releases the lock.
6. Lock release: Once the holder of the lock has finished operating on the shared resource, they will send a request to the lock service to release the lock.
7. When a release request is received by the lock service, the lock’s status will be changed to unoccupied and the lock’s holder will be set to null.

This is how distributed locks work in Java. By using distributed locks, it is possible to coordinate between multiple threads or processes to prevent resource contention and data inconsistency. Common implementations of distributed locks include database-based, cache-based (such as Redis’ setnx command), and Zookeeper-based implementations.