Node.js connect to MySQL Docker container ECONNREFUSED - mysql

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"]
Note: wait-for-it.sh script comes from: https://github.com/vishnubob/wait-for-it