Docker Nodejs ERROR: connect ECONNREFUSED 127.0.0.1:3306, how to connect to MySQL?

Question

Node.js

Hello!
I am developing a site on nodejs + express + sequelize-cli
There was a task for development to deploy everything through docker.
You need to run mysql, adminer, backend at startup Docker

-compose.yml file:

version: '3'

services:
  backend:
    build: ./backend
    ports:
      - 5000:5000

  db:
    image: mysql
    command: --default-authentication-plugin=mysql_native_password
    restart: always
    environment:
      MYSQL_DATABASE: database_development
      MYSQL_ROOT_PASSWORD: password_development

  adminer:
    image: adminer
    restart: always
    ports:
      - 8080:8080

Dockerfile (backend):

FROM node:latest

COPY . /app

WORKDIR /app

RUN npm install
RUN npx sequelize db:migrate
RUN npx sequelize db:seed:all

EXPOSE 5000

VOLUME .:/app

CMD npm run dev

After running the command: docker-composer up

This error appears:

Step 5/9 : RUN npx sequelize db:migrate
 ---> Running in 08fd366ceb86

Sequelize CLI [Node: 15.5.0, CLI: 6.2.0, ORM: 6.3.5]

Loaded configuration file "database/config.json".
Using environment "development".

ERROR: connect ECONNREFUSED 127.0.0.1:3306

npm ERR! code 1
npm ERR! path /app
npm ERR! command failed
npm ERR! command sh -c sequelize db:migrate

npm ERR! A complete log of this run can be found in:
npm ERR!     /root/.npm/_logs/2020-12-28T07_22_31_094Z-debug.log
ERROR: Service 'backend' failed to build : The command '/bin/sh -c npx sequelize db:migrate' returned a non-zero code: 1

As I understand it is not connected to the database. On the Internet, it was advised to use depends_on, after applying depends_on, the build order just changed, but the error remained ... Tell me how to fix it. Thank you!

Answer 1

read how the network is arranged in docker.
you need to connect not to 127.0.0.1:3306 , but to db:3306