NodeJS can't connect to MySQL database

Question

i'm trying to build a web app using NodeJS (with expressJS) as backend and MySQL for the database. This is all built and used with a docker-compose.yml, and a dockerfile for nodejs.

Problem is, the server can't connect to the database, it keep giving me this error in docker-compose logs :

/usr/src/app/server.js:17
        if (err) throw err
                 ^

Error: connect ECONNREFUSED 127.0.0.1:3606
    at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1300:16)
    --------------------
    at Protocol._enqueue (/usr/src/app/node_modules/mysql/lib/protocol/Protocol.js:144:48)
    at Protocol.handshake (/usr/src/app/node_modules/mysql/lib/protocol/Protocol.js:51:23)
    at PoolConnection.connect (/usr/src/app/node_modules/mysql/lib/Connection.js:116:18)
    at Pool.getConnection (/usr/src/app/node_modules/mysql/lib/Pool.js:48:16)
    at startServer (/usr/src/app/server.js:16:10)
    at Object. (/usr/src/app/server.js:28:1)
    at Module._compile (node:internal/modules/cjs/loader:1119:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1173:10)
    at Module.load (node:internal/modules/cjs/loader:997:32)
    at Module._load (node:internal/modules/cjs/loader:838:12) {
  errno: -111,
  code: 'ECONNREFUSED',
  syscall: 'connect',
  address: '127.0.0.1',
  port: 3606,
  fatal: true
}

Here is my docker-compose.yml :

services:
  db:
    image: mysql:latest
    restart: unless-stopped
    environment:
      - MYSQL_DATABASE = areadb
      - MYSQL_ROOT_PASSWORD = password
    ports:
      - 3606:3606
    volumes:
      - sql-db:/var/lib/mysql
    networks:
      - backend

  server:
    depends_on:
      - db
    build: ./server
    restart: unless-stopped
    environment:
      - MYSQL_DATABASE = areadb
      - MYSQL_USER = root
      - MYSQL_PASSWORD = password
      - MYSQL_HOST = db
    ports:
      - 8080:8080
    networks:
      - backend

networks:
  backend:

volumes:
  sql-db:

And the server.js file that is used at the start :

const express = require("express");
const mysql = require("mysql");

function startServer() {
    const app = express();
    const port = 8080;
    const pool = mysql.createPool({
        connectionLimit: 10,
        host: "127.0.0.1",
        user: "root",
        password: "password",
        database: "areadb",
        port: "3606"
    });

    pool.getConnection(function (err, connection) {
        if (err) throw err
        else console.log("App successfully connected to MySQL database.");
    });
    app.get("/", (req, res) => {
        res.send("Hello World");
    });
    app.listen(port, function () {
        console.log("Listening on port 8080");
    });
}

startServer();

Please help me understand why this error happens and how can I fix it.

robertklep · Answer

Notice how the correct connection information is all present in your docker-compose.yml:

    environment:
      - MYSQL_DATABASE = areadb
      - MYSQL_USER = root
      - MYSQL_PASSWORD = password
      - MYSQL_HOST = db

So it would be a shame not to use it in your server.js:

host: process.env.MYSQL_HOST,
user: process.env.MYSQL_USER,
password: process.env.MYSQL_PASSWORD,
database: process.env.MYSQL_DATABASE,
port: 3606 // might also want to make this an environment variable

An an aside, instead of port 3606 I think you mean 3306, which is the default MySQL port.

NodeJS can't connect to MySQL database

1 Answers