Cache update mechanism in Java caching technology

Java caching technology is becoming more and more common in modern software development because of its ability to significantly improve application responsiveness and performance. In use, we often encounter the problem of updating cached data. This article will introduce the cache update mechanism in Java cache technology.

1. Cache update strategy

In applications, cache data update strategies mainly include the following:

1. Regular refresh

Scheduled refresh is one of the most common cache update strategies. In this case, the program periodically checks the cache item's timestamp or other data, and if the data is out of date, it removes it from the cache and reloads the latest data.

This method can ensure timely refresh of data, but it will reduce system performance during the update period, and the data refresh cycle needs to match the system load and data update frequency.

2. Refresh on update

In the refresh on update strategy, cache items are reloaded when updated. This strategy requires the ability of the cache user to intervene when data is updated. .

This strategy can avoid the performance degradation caused by scheduled refresh, but requires additional code to support data update logic.

3. Asynchronous refresh

Asynchronous refresh is a relatively complex solution. In this case, cached read requests are stored in an asynchronous queue similar to a message queue. When a cache item expires, the program re-reads the data with a read request in the asynchronous queue, and then updates the cache with the new data.

This solution can ensure high performance of the system and timely updating of data, but it requires additional development investment and system management investment.

2. Cache update mechanism

Common cache update mechanisms include the following:

1. Cache clearing

Cache clearing is One of the simplest cache update mechanisms. In this case, the program will directly clear all cache items and reload the latest data.

This method is relatively violent and inefficient, but it is also a good solution in some specific scenarios.

2. Cache invalidation

Cache invalidation is a popular cache update mechanism. In this case, the cache item is marked as expired, and the program reloads the data the next time it is read. This mechanism requires a successful synchronization process between the timestamp of the cache item and the update time of the data.

This solution is relatively simple, but there will also be additional performance overhead issues caused by cache items that may expire between multiple requests.

3. Cache eviction

Cache eviction is a mechanism to clear cache items after they reach a certain number or exceed a specific number of operations. In this case, the program will determine the cache items that need to be eliminated based on a series of algorithms (such as LRU).

This method is relatively controllable and efficient, but there are certain risks, because it may cause business problems when choosing which cache item to eliminate.

3. Precautions for cache update

In the process of using cache, we need to pay attention to the following points:

1. The cache should be updated in time, but do not refresh frequently

In order to ensure the accuracy of the data, the frequency of cache updates must match the frequency of data updates. On this basis, the program also needs to take into account system load and performance. Both the scheduled refresh mechanism and the asynchronous refresh mechanism can solve this problem.

2. Please try to avoid locks when updating the cache

When multiple threads update the same cache item at the same time, lock competition may occur. In this case, the program must require lock management to ensure concurrency safety. In order to avoid lock competition, it can be solved by refreshing the mechanism during update.

3. Pay attention to null values ​​in the cache

The program should ensure that there are no null values ​​in the cache. When reading cache entries, programs should return a default value to avoid throwing exceptions. Otherwise, unexpected results may occur when the program returns a null value.

Summary

The cache update mechanism in Java cache technology is an important means to improve system performance and response time. When choosing a specific caching strategy and cache update mechanism, we need to consider data accuracy and system performance. In addition, we also need to ensure the concurrency safety and data consistency of cache operations.

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