How nodejs uses caching

With the development of the Internet, network applications are becoming more and more complex, and there are more and more access requests. To improve application performance, caching has become an important option, and Node.js, as a fast server-side JavaScript language, also supports multiple ways to use caching. This article will introduce how Node.js uses caching to improve application performance.

1. Basic principles of caching

Cache can save some frequently used data in memory or disk. When the data needs to be used, it can be obtained directly from the cache, reducing the need for each query time, improving the response speed of the system. Caches generally store data in the form of key-value pairs, where keys can be any type of data and values ​​can be strings, numbers, JavaScript objects, or other data types.

In Node.js, we can use the core module cache to create our own cache. This module provides the following methods:

• cache.get(key): Get the data corresponding to the specified key value.
• cache.set(key, value, ttl): Store the specified value into the cache, using the specified key as the identifier. ttl represents the time to live (Time To Live in English), that is, within this time, the data can be accessed from the cache.
• cache.del(key): Delete the data corresponding to the specified key value.
• cache.clear(): Clear all caches.

It should be noted that the data cached using the built-in cache module of Node.js can only be shared within the current process and cannot be shared between processes. If you need to achieve inter-process sharing, you can use a third-party cache module, such as Memcached or Redis.

2. Use the built-in cache module of Node.js

In actual development, we can use the built-in cache module of Node.js to cache data. Here is a simple example:

const cache = require('cache');
let data = null;

if (cache.get('data')) {
  data = cache.get('data');
} else {
  // 数据库查询操作
  data = db.query('SELECT * FROM users');
  // 将数据存储到缓存中，使用'users'作为键，存活时间为1小时
  cache.set('users', data, 3600);
}

// 使用data数据

In the above example, we first try to get the data from the cache, and if the corresponding key is found, the data in the cache is used directly. If not found, the database is queried and the queried data is stored in the cache to reduce the number of database queries. The survival time of this data is 1 hour. After expiration, you need to re-query the database and update the data in the cache.

3. Use Redis cache

In addition to using the built-in cache module of Node.js, we can also use third-party cache modules, such as Redis. Redis is a memory-based cache database that enables caching of Internet applications. The following is an example of using Redis cache:

const redis = require('redis');
const client = redis.createClient();

let data = null;
client.get('users', (err, result) => {
  if (result) {
    data = result;
  } else {
    // 数据库查询操作
    data = db.query('SELECT * FROM users');
    // 将数据存储到Redis中，使用'users'作为键，存活时间为1小时
    client.setex('users', 3600, JSON.stringify(data));
  }
});

// 使用data数据

In the above example, we use Redis's get method to obtain data. If the corresponding key is found, the cache is used directly. data in. If not found, query the database and store the queried data in Redis to reduce the number of database queries. The survival time of this data is 1 hour. After expiration, you need to re-query the database and update the data in Redis.

4. Cache invalidation processing

The cached data always remains the same during the survival time, but when the cached data expires, the database needs to be re-queried and the data in the cache needs to be updated. In order to ensure the real-time nature of the data, we can use a timer to regularly clear expired data in the cache. For example, clear the cache every 5 minutes:

setInterval(() => {
  cache.clear();
}, 300000);

In the above example, we use the setInterval method to regularly clear expired data in the cache. The time interval is 5 minutes, that is, every Clean every 5 minutes.

5. Caching strategies

When using cache, you need to consider some caching strategies to improve application performance.

1. Cache elimination strategy

The cache elimination strategy means that after the cache reaches a certain size or the survival time reaches a certain period, some elimination strategies need to be adopted to clean up the data in the cache. . Common elimination strategies are:

• FIFO (first in, first out): clear out the data that first enters the cache.
• LIFO (last in, first out): Clear out the last data that entered the cache.
• LFU (Least Recently Used): Clear the data with the least usage.
• LRU (most recently unused): Clear the most recently unused data.

In actual development, different elimination strategies can be adopted according to specific application scenarios to improve cache efficiency.

2. Cache update strategy

The cache update strategy refers to how to ensure that the data in the cache remains synchronized with the data in the database when the data in the database is updated. Common cache update strategies are:

• Cache-Aside (bypass cache): When we need to read a piece of data, we first search it from the cache, and return it directly if it is found. Otherwise, we query it from the database and store the queried data in the cache. in and return data. When we need to update data, we first update the data in the database, and then delete the data from the cache. When we read the data again, we will read it from the database again and update the data in the cache.
• Write-Through (write-through cache): When we need to insert or update a piece of data, we first update the data in the database, and then store the data in the cache. When we need to read a piece of data, we first search it from the cache, and return it directly if it is found. Otherwise, we query it from the database, store the queried data in the cache, and return the data. When data needs to be deleted, we first delete the data in the database and then delete the data from the cache.

In actual development, different cache update strategies can be adopted according to specific application scenarios to ensure data consistency between the cache and the database.

6. Summary

Caching is one of the important means to improve application performance. In Node.js, we can use the built-in cache module to implement caching, or we can use third-party caching modules, such as Redis. When using cache, you need to consider cache elimination strategies and cache update strategies to improve cache efficiency and data consistency. While caching can improve application performance, there are also cache security and management costs to be aware of.

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