Distributed locks in Java caching technology

Java caching technology has become an indispensable part of modern IT architecture, and distributed locks are an indispensable technical means when processing cached data. This article will introduce distributed locks in Java cache technology, including its principles, applications, and some precautions in use.

1. Principle of distributed locks
Before discussing distributed locks, we need to understand some common lock types, such as pessimistic locks and optimistic locks. Pessimistic locking locks the resource before executing the operation to prevent other processes from acquiring the resource, and then releases the lock after the operation is completed; optimistic locking does not lock the resource before executing the operation, but compares the version number after the operation is completed. Make judgments in other ways to avoid problems caused by concurrent operations.

In a distributed environment, traditional stand-alone locks can no longer meet the lock requirements, so distributed locks appear. The principle of distributed lock is to use shared memory to store lock information in the shared memory, and to realize lock control through communication and coordination between multiple processes. Distributed locks need to meet the following characteristics:

• Reentrancy: the same thread can acquire the same lock repeatedly.
• Deadlock can be avoided: If a thread holds a lock but does not release the lock for some reason, other threads can avoid deadlock by reserving locks and other methods.
• Mutually exclusive: only one thread can occupy the lock at any time.

2. Application of distributed locks
Distributed locks are widely used in data caching in distributed environments, such as dynamic web pages, database connection objects, local caches, etc. Among them, it is especially widely used in web applications and database connection pools. In some scenarios, we need to ensure that the data in the cache must be the latest, which requires the use of distributed locks to complete access control of cached data.

For example, we need a globally unique activity counter. In order to ensure that the counter does not repeat, we need to use distributed locks to control access to the counter. In Java, common distributed lock implementations are:

• Redis-based distributed lock: Create a distributed lock implementation by using the SETNX command of Redis.
• Zookeeper-based distributed lock: implemented by using Zookeeper’s node monitoring mechanism.

3. Precautions for using distributed locks
When using distributed locks, you need to pay attention to the following points:

• The granularity of the lock should be as small as possible , to prevent the lock from blocking other operations.
• The locking time should be as short as possible. If the lock is held for a long time, it may cause network problems or deadlock.
• Avoid repeated lock acquisition operations to avoid causing an infinite loop.
• Manually release the lock to ensure resource release and lock deletion.

4. Summary
Distributed locks are an important part of Java caching technology. By using distributed locks to control access to cached data, problems such as data duplication or inconsistency can be avoided. . Using distributed locks correctly and following relevant precautions can improve the performance and reliability of distributed systems.

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