Cache reconstruction mechanism in Java caching technology

In developing high-performance applications, caching technology is an indispensable part. Caching technology is also very common in Java development, but a very important problem will be encountered during the use of cache, which is the update and reconstruction of cache data. This article will introduce the cache reconstruction mechanism in Java caching technology to help readers better understand and use caching technology.

1. The concept and function of the cache reconstruction mechanism

The cache reconstruction mechanism refers to how to update the cache data in a timely manner in the cache system when the cache data changes or expires to ensure that the data accuracy and timeliness.

The cache reconstruction mechanism mainly has the following three aspects:

1. Improve the timeliness of cached data

Because the data in the cache is previously obtained from the database or other data The cached data is queried from the source, so cached data gradually loses their authenticity over time. Through the cache reconstruction mechanism, cached data can be updated in a timely manner to ensure the timeliness of the data and avoid problems caused by using expired data.

2. Improve the accuracy of cached data

When cached data changes, if the cached data is not updated in time, incorrect data results will be obtained when subsequent reads of the cache. Through the cache reconstruction mechanism, cached data can be updated in a timely manner to ensure data accuracy and avoid problems caused by using incorrect data.

3. Avoid the cache avalanche effect

When a large amount of cached data expires at the same time, or the system pressure is too high, the cache avalanche effect may occur. This situation can be avoided by updating the cache data in a timely manner through the cache reconstruction mechanism.

2. Implementation method of cache reconstruction mechanism

According to the implementation method of Java cache technology, it can be divided into two categories: local cache and remote cache. In different cache implementations, the cache reconstruction mechanism is implemented in different ways.

1. Cache reconstruction mechanism in local cache

Local cache is generally a memory-based cache, and the application manages cache data by itself. In the local cache, the cache reconstruction mechanism can be implemented in the following ways:

(1) Clear expired cache data regularly

The data in the local cache usually has a certain timeliness, so Expired cached data needs to be cleared regularly. Regularly clearing expired cache data is a simple and effective cache reconstruction mechanism.

(2) Manually refresh the cached data

When the cached data changes, manually refreshing the cached data is a common implementation method. By manually refreshing the cached data, the cached data can be updated in a timely manner to ensure the accuracy and timeliness of the data. However, manually refreshing cache data requires the application to manage it by itself, and thread safety issues need to be paid attention to.

(3) Asynchronous refresh of cache data

Asynchronous refresh of cache data is a commonly used cache reconstruction mechanism. Asynchronous refresh of cache data can be performed by placing the update operation in another thread without affecting the running of the application. However, asynchronous refresh of cached data also carries certain risks. If the cached data cannot be updated in time, data inconsistency may result.

2. Cache reconstruction mechanism in remote cache

Remote cache is generally managed by a central cache server, and multiple clients can share the same cache data. In remote caching, the cache reconstruction mechanism is usually implemented by the central cache server.

(1) Read and write separation

In the design of read and write separation, read operations use cached data, and write operations update the data in the database. When the write operation is completed, the central cache server will use asynchronous refresh of cache data to update the cache data, thereby ensuring the accuracy and timeliness of the cache data.

(2) Subscription and publishing mechanism

In the subscription and publishing mechanism, the client can subscribe to changes in a certain data source. When the data in the data source changes, the central cache server will automatically update Caching data can ensure the timeliness of data.

(3) Cluster synchronization

In the design of cluster synchronization, data is synchronized between multiple cache servers to ensure data consistency in all cache servers. Cluster synchronization is a relatively complex design method that requires maintaining communication and synchronization between cache servers.

3. Application examples of cache reconstruction mechanism

The cache reconstruction mechanism has many application scenarios in actual applications. The following are some examples of practical application scenarios:

(1) Product price changes on e-commerce websites

Product prices on e-commerce websites are easy to change. If the application directly uses the price data in the database, a database query will be required for each access, which will reduce system performance. . Through the cache reconstruction mechanism, cached data can be updated in time when prices change, ensuring that the price data at the time of access is correct.

(2) Bank transaction query data

Bank transaction query data is a complex system that needs to process a large amount of transaction data efficiently. Through the cache reconstruction mechanism, query results can be cached in memory to improve query efficiency. When the transaction data is updated, the cached data is updated in a timely manner to ensure the accuracy of the query results.

(3) Social network friend list

The friend list of social networks changes frequently. If the database needs to be queried every time it is accessed, performance will be seriously affected. Through the cache reconstruction mechanism, the friend list can be cached in memory to improve performance. When the friend list changes, the cached data is updated in a timely manner to ensure the accuracy of the friend list.

4. How to ensure the cache reconstruction mechanism

The method of ensuring the cache reconstruction mechanism is a very important issue, which mainly includes the following aspects:

(1) Thread safety

The cache reconstruction mechanism needs to consider thread safety issues. During concurrent access by multiple threads, the correctness of cached data needs to be ensured, and thread safety issues also need to be considered.

(2) Retry on failure

The cache reconstruction mechanism needs to consider the handling of abnormal situations. If the cache data update fails, a retry is required to ensure that the data can be updated in time.

(3) Logging

In the implementation of the cache reconstruction mechanism, it is necessary to log the reconstruction operation to facilitate troubleshooting and processing when problems occur.

5. Summary

Through the introduction of the cache reconstruction mechanism in Java cache technology, readers can understand that in practical applications, the cache reconstruction mechanism is a very critical link and can improve the application Program performance and reliability. In practical applications, readers can choose different cache implementation methods and cache reconstruction mechanisms according to their actual needs. At the same time, attention needs to be paid to the security and reliability of the cache reconstruction mechanism to ensure that data can be updated accurately and timely.

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