Node.js连接到MySQL Docker容器ECONNREFUSED

Question

Before you flag this question as a duplicate, please note that I did read other answers, but it didn't solve my problem.

I have a Docker compose file consisting of two services:

version: "3"
services:
  mysql:
    image: mysql:5.7
    environment:
      MYSQL_HOST: localhost
      MYSQL_DATABASE: mydb
      MYSQL_USER: mysql
      MYSQL_PASSWORD: 1234
      MYSQL_ROOT_PASSWORD: root
    ports:
      - "3307:3306"
    expose:
      - 3307
    volumes:
      - /var/lib/mysql
      - ./mysql/migrations:/docker-entrypoint-initdb.d
    restart: unless-stopped
  web:
    build:
      context: .
      dockerfile: web/Dockerfile
    volumes:
      - ./:/web
    ports:
      - "3000:3000"
    environment:
      NODE_ENV: development
      PORT: 3000
    links:
      - mysql:mysql
    depends_on:
      - mysql
    expose:
      - 3000
    command: ["./wait-for-it.sh", "mysql:3307"]

/web/Dockerfile:

FROM node:6.11.1

RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

COPY package.json /usr/src/app/
RUN npm install

COPY . /usr/src/app

CMD [ "npm", "start" ]

After docker-compose up --build the services start up, however the "wait-for-it.sh" script times out when waiting for mySQL to start (so temporarily I am not using it when testing for DB connectivity, I just wait until the console shows that MySQL is ready for accepting incoming connections)

When MySQL is running from the host machine I can login using Sequel Pro and query the DB and get the sample records from ./mysql/migrations

I can also SSH into the running MySQL container and do the same.

However, my Node.js app yields ECONNREFUSED 127.0.0.1:3307 when connecting

MySQL init:

import * as mysql from 'promise-mysql'

const config = {
    host: 'localhost',
    database: 'mydb',
    port: '3307',
    user: 'mysql',
    password: '1234',
    connectionLimit: 10
}

export let db = mysql.createPool(config);

MySQL query:

import { db } from '../db/client'

export let get = () => {

return db.query('SELECT * FROM users', [])
    .then((results) => {
        return results

    })
    .catch((e) => {
        return Promise.reject(e)
    })
}

Route invoked when hitting url /

import { Router } from 'express';
import * as repository from '../repository'
export let router = Router();

router.get('/', async (req, res) => {

    let users;

    try{
        users = await repository.users.get();
    } catch(e){
        // ECONNREFUSED 127.0.0.1:3307
    }

    res.render('index', {
        users: users
    });
});

It's unlikely to be a race condition because at the same time when Node.js fails I can query using Sequel Pro or SSH into the running Docker container and query. So it's probably a case of Node.js not being able to access to MySQL container?

{
    error: connect ECONNREFUSED 127.0.0.1:3307
    code: 'ECONNREFUSED',
    errno: 'ECONNREFUSED',
    syscall: 'connect',
    address: '127.0.0.1',
    port: 3307,
    fatal: true
}

Answer 1

This:

mysql:
    image: mysql:5.7
    environment:
    ...
    ports:
      - "3307:3306"

Means that Docker will map the 3307 port of the host to the 3306 port of the container. So you can access from Sequel to localhost:3307 .

However, it does not mean that the container is listenting to 3307 ; the container is in fact still listening to 3306 . When others containers tries to access the mysql DNS, it gets translated to the internal container IP, therefore you must connect to 3306 .

So your node config should look like:

const config = {
    host: 'mysql',
    database: 'mydb',
    port: '3306',
    user: 'mysql',
    password: '1234',
    connectionLimit: 10
}

And this in your docker-compose.yml:

command: ["./wait-for-it.sh", "mysql:3306"]