Docker环境下Express/NodeJS无法连接Redis但MySQL正常的问题

问题 #

核心问题：NodeJS本地运行时可正常连接MySQL和Redis；Docker容器中运行时仅能连接MySQL，无法连接Redis。

Docker Compose配置 #

version: '3'
services:
    express-app:
        build:
            context: .
        ports:
            - 3000:3000
        depends_on:
            - redis-db
            - mysql-db
        environment:
            - MYSQL_HOST=mysql-db
            - REDIS_HOST=redis-db

    mysql-db:
        image: mysql:latest
        environment:
            MYSQL_DATABASE: twitter
            MYSQL_USER: user
            MYSQL_PASSWORD: user-password
            MYSQL_ROOT_PASSWORD: root-password
        ports:
            - '3306:3306'
        volumes:
            - my-twitter-db-mount:/var/lib/mysql

    redis-db:
        image: redis
        ports:
            - '6379:6379'
        volumes:
            - my-twitter-redis-mount:/var/lib/redis/data

volumes:
    my-twitter-db-mount:
    my-twitter-redis-mount:

NodeJS代码 #

const mysql = require('mysql2');
const redis = require('redis');

var connection;
var redisConnection;
const getConnection = (() => {
    console.log("################ "+process.env.MYSQL_HOST) ;
    console.log("################ "+process.env.REDIS_HOST) ;
    
    connection = mysql.createConnection({
        host: process.env.MYSQL_HOST || 'localhost',
        port: 3306,
        user: 'user',
        password: 'user-password'
    });
    
    redisConnection = redis.createClient({
        port: 6379,
        host: process.env.REDIS_HOST || 'localhost'
    });
    
    connection.connect();
    redisConnection.connect();
});

const queryFollowers = (async (ownerId) => {
    getConnection();
    let val = await redisConnection.get(`OwnerCache_${ownerId}`);
    if (val) {
        console.log("Returning the cached value "+val);
        return new Promise((resolve, reject)  => resolve(val));
    }
    console.log("No Cached value found for "+val+ " Querying database...");
    return new Promise((resolve, reject) => { 
        connection.query(`SELECT * from twitter.Users where id IN  (SELECT follower_id from twitter.User_Follower  WHERE user_id = ${ownerId})`, (err, rows, fields) => {
            if (err) reject(err);
            console.log("ROWS "+rows);
            let followers = [];
            if(rows.length > 0)  {
                rows.forEach(user => {
                    followers.push(user);
                });
                redisConnection.set(`OwnerCache_${ownerId}`, JSON.stringify(followers));
                redisConnection.expire(`OwnerCache_${ownerId}`, 10);
                resolve(followers);
            }
        });
    });
});

错误信息 #

使用桥接网络名称mysql-db可正常连接MySQL，但使用redis-db却无法连接Redis（本地运行时Node可连接两者，此时默认使用localhost）。

Listening on port 3000
Returning all the followers for ownerID 1
################ mysql-db
################ redis-db
node:internal/process/promises:288
            triggerUncaughtException(err, true /* fromPromise */);
            ^
Error: connect ECONNREFUSED 127.0.0.1:6379
    at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1246:16)
Emitted 'error' event on Commander instance at:
    at RedisSocket.<anonymous> (/app/node_modules/@node-redis/client/dist/lib/client/index.js:339:14)
    at RedisSocket.emit (node:events:513:28)
    at RedisSocket._RedisSocket_connect (/app/node_modules/@node-redis/client/dist/lib/client/socket.js:117:14)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async Commander.connect (/app/node_modules/@node-redis/client/dist/lib/client/index.js:162:9) {
  errno: -111,
  code: 'ECONNREFUSED',
  syscall: 'connect',
  address: '127.0.0.1',
  port: 6379
}
Node.js v18.6.0

解决思路 #

1. 修正Redis客户端参数格式
   你使用的是@node-redis/client（v4+版本），该版本不再支持将host和port作为顶级参数传入createClient，需要嵌套在socket对象中，或者使用URL格式：

   // 方式1：使用socket对象
   redisConnection = redis.createClient({
       socket: {
           host: process.env.REDIS_HOST || 'localhost',
           port: 6379
       }
   });
   
   // 方式2：使用URL格式
   redisConnection = redis.createClient({
       url: `redis://${process.env.REDIS_HOST || 'localhost'}:6379`
   });
   

2. 确保Redis服务就绪后再连接
   depends_on仅保证容器启动顺序，不保证Redis服务完全就绪。可以在代码中添加重试逻辑：

   async function connectRedis() {
       try {
           await redisConnection.connect();
           console.log('Redis连接成功');
       } catch (err) {
           console.log('Redis连接失败，2秒后重试...');
           setTimeout(connectRedis, 2000);
       }
   }
   // 替换原redisConnection.connect()为connectRedis()
   

3. 验证容器间网络连通性
   进入express-app容器，执行以下命令测试与Redis容器的网络连通性：

   docker exec -it <express-app容器ID> ping redis-db
   docker exec -it <express-app容器ID> telnet redis-db 6379
   

   如果telnet不通，查看Redis容器日志排查启动问题：

   docker logs redis-db
   

4. 检查Redis挂载目录权限
   Redis容器默认使用redis用户运行，若挂载目录权限不正确会导致服务启动失败。可以在docker-compose.yml中显式指定用户：

   redis-db:
       image: redis
       ports:
           - '6379:6379'
       volumes:
           - my-twitter-redis-mount:/var/lib/redis/data
       command: redis-server --appendonly yes
       user: "redis"
   

内容的提问来源于stack exchange，提问作者Frederick Scott Smith