nodejs dockerized app can't connect to mariadb dockerized database

Question

My setup is :

• Mariadb container with dockerfile launched through docker-compose
• NodeJs container with dockerfile launched through docker-compose

My issue :

I can't connect my nodejs app to the database. I can access the database locally through dbeaver or command line so I know it's working. But when I try to access it thourgh my index.js I get the following error :

Error: connect ECONNREFUSED 127.0.0.1:3306
at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1141:16)
From event:
at _registerHandshakeCmd (/usr/src/app/node_modules/mariadb/lib/connection.js:689:11)
at /usr/src/app/node_modules/mariadb/lib/connection.js:57:11
at new Promise (<anonymous>)
at Connection.connect (/usr/src/app/node_modules/mariadb/lib/connection.js:56:16)
at Object.createConnection (/usr/src/app/node_modules/mariadb/promise.js:17:36)
at Object.<anonymous> (/usr/src/app/src/index.js:24:28)
at Module._compile (internal/modules/cjs/loader.js:1147:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1167:10)
at Module.load (internal/modules/cjs/loader.js:996:32)
at Function.Module._load (internal/modules/cjs/loader.js:896:14) {
    errno: -111,
    code: 'ECONNREFUSED',
    syscall: 'connect',
    address: '127.0.0.1',
    port: 3306,
    fatal: true
}

NodeJs Dockerfile:

FROM node:latest
WORKDIR /usr/src/app
COPY package*.json /usr/usr/app
RUN npm install
COPY . /usr/src/app
EXPOSE 8080
CMD ["npm", "start"]

Mariadb Dockerfile:

FROM mariadb:latest
ENV MYSQL_ROOT_PASSWORD=mdp
ENV MYSQL_DATABASE=dashboard
ENV MYSQL_USER=monty
ENV MYSQL_PASSWORD=monty
USER 1000
EXPOSE 3306

docker-compose.yml:

version: '3'
services: 
    web:
        build: ./backend
        ports:
            - "8080:8080"
        volumes:
            - ./backend:/usr/src/app/
        working_dir: /usr/src/app
        environment:
            - MARIADB_HOST=database
            - MARIADB_PORT_NUMBER=3306
            - MARIADB_USER=monty
            - MARIADB_PASSWORD=monty
            - MARIADB_DATABASE=dashboard
        user: "1000"
        container_name: backend
        depends_on:
            - database
        links:
            - database:database
    database:
        build: ./database
        ports:
            - "3306:3306"
        expose:
            - "3306"
        volumes:
            - /database/data:/var/lib/mysql:rw
        user: "1000"
        hostname: "localhost"
        environment:
            - ALLOW_EMPTY_PASSWORD=yes
            - MARIADB_DATABASE=dashboard
            - MARIADB_PORT=3306
            - MARIADB_USER=monty
            - MARIADB_PASSWORD=monty
        container_name: database

And here is my index.js:

const express = require('express')
const mariadb = require('mariadb');
const cors = require('cors');
const bodyParser = require('body-parser');
const app = express();
app.use(
    bodyParser.urlencoded({
        extended: true
    })
)
app.use(cors());

app.get('/', (req, res) => {
    res.send('hello world');
});

const connection = mariadb.createConnection({
    host: '127.0.0.1',
    user: 'someuser',
    password: 'somepassword',
    database: 'dashboard',
    port: '3306',
}).then(conn => {
    console.log('connection established.');
}).catch(err => {
    console.log(err);
});

app.listen(8080);

If anyone has any tips regarding where to look or where the error might come from I'd be grateful. Thanks!

Answer 1

You are using 127.0.0.1 as db host name in your NodeJS application. But that is the IP address of your NodeJS container. Every container has its own IP address (exception: using docker network host). This causes the error:

Error: connect ECONNREFUSED 127.0.0.1:3306

When using docker-compose, you can access the db using the service name you specified in the docker-compose.yml file. In your example the service name database can be used as host name. Try this:

const connection = mariadb.createConnection({
    host: 'database',
    ...