面试题：Node.js 多线程与网络请求结合时的资源管理与错误处理

管理线程间共享资源（以数据库连接池为例）

使用线程安全的数据结构 在 Node.js 中，可以借助 worker_threads 模块来实现多线程。对于数据库连接池这种共享资源，可以使用线程安全的数据结构来管理。例如，使用 Map 来存储连接池，并对其访问进行同步控制。

const { Worker, isMainThread, parentPort } = require('worker_threads');
const mysql = require('mysql2');

if (isMainThread) {
    const connectionPool = mysql.createPool({
        host: 'localhost',
        user: 'root',
        password: 'password',
        database: 'test',
        connectionLimit: 10
    });
    const worker = new Worker(__filename);
    worker.on('message', (message) => {
        console.log('Main thread received:', message);
    });
    worker.postMessage({ connectionPool });
} else {
    parentPort.on('message', (message) => {
        const { connectionPool } = message;
        connectionPool.getConnection((err, connection) => {
            if (err) throw err;
            connection.query('SELECT 1 + 1 AS solution', (error, results, fields) => {
                connection.release();
                if (error) throw error;
                parentPort.postMessage(`Query result: ${results[0].solution}`);
            });
        });
    });
}

锁机制 为了防止多个线程同时访问和修改共享资源（如连接池中的连接），可以引入锁机制。虽然 Node.js 没有内置的锁，但可以通过 Atomics 和 SharedArrayBuffer 来模拟简单的锁。

const { Worker, isMainThread, parentPort, SharedArrayBuffer, Atomics } = require('worker_threads');
const mysql = require('mysql2');

// 模拟锁
class SimpleLock {
    constructor() {
        this.lock = new SharedArrayBuffer(1);
        this.int32View = new Int32Array(this.lock);
        this.int32View[0] = 0;
    }
    acquire() {
        while (Atomics.compareExchange(this.int32View, 0, 0, 1) !== 0);
    }
    release() {
        Atomics.store(this.int32View, 0, 0);
    }
}

if (isMainThread) {
    const connectionPool = mysql.createPool({
        host: 'localhost',
        user: 'root',
        password: 'password',
        database: 'test',
        connectionLimit: 10
    });
    const lock = new SimpleLock();
    const worker = new Worker(__filename);
    worker.on('message', (message) => {
        console.log('Main thread received:', message);
    });
    worker.postMessage({ connectionPool, lock });
} else {
    parentPort.on('message', (message) => {
        const { connectionPool, lock } = message;
        lock.acquire();
        connectionPool.getConnection((err, connection) => {
            lock.release();
            if (err) throw err;
            connection.query('SELECT 1 + 1 AS solution', (error, results, fields) => {
                connection.release();
                if (error) throw error;
                parentPort.postMessage(`Query result: ${results[0].solution}`);
            });
        });
    });
}

优雅处理网络请求错误

网络超时处理 使用 Promise.race 和 setTimeout 来实现网络请求超时。

const fetch = require('node-fetch');

function fetchWithTimeout(url, options = {}, timeout = 5000) {
    return Promise.race([
        fetch(url, options),
        new Promise((_, reject) => {
            setTimeout(() => {
                reject(new Error('Network request timed out'));
            }, timeout);
        })
    ]);
}

fetchWithTimeout('https://example.com', {}, 3000)
   .then(response => response.text())
   .then(data => console.log(data))
   .catch(error => console.error('Error:', error.message));

请求被拒绝处理 在 fetch 或其他网络请求库的 catch 块中捕获请求被拒绝的错误（如 403 状态码等）。

fetch('https://example.com')
   .then(response => {
        if (!response.ok) {
            throw new Error(`Request was rejected with status ${response.status}`);
        }
        return response.text();
    })
   .then(data => console.log(data))
   .catch(error => console.error('Error:', error.message));

综合错误处理 结合上述两种情况，以及其他可能的网络请求错误，进行统一的错误处理。

function fetchWithErrorHandling(url, options = {}, timeout = 5000) {
    return Promise.race([
        fetch(url, options)
           .then(response => {
                if (!response.ok) {
                    throw new Error(`Request was rejected with status ${response.status}`);
                }
                return response.text();
            }),
        new Promise((_, reject) => {
            setTimeout(() => {
                reject(new Error('Network request timed out'));
            }, timeout);
        })
    ]);
}

fetchWithErrorHandling('https://example.com', {}, 3000)
   .then(data => console.log(data))
   .catch(error => console.error('Error:', error.message));

星途面试题库

面试题：Node.js 多线程与网络请求结合时的资源管理与错误处理

知识考点

面试题答案

管理线程间共享资源（以数据库连接池为例）

优雅处理网络请求错误