I am using docker compose with my app and are trying to connect mongodb to the server. When i run my app locally outside of docker i get this as output(works as intended)

[nodemon] 2.0.15
[nodemon] to restart at any time, enter `rs`
[nodemon] watching path(s): *.*
[nodemon] watching extensions: js,mjs,json
[nodemon] starting `node index.js`
Server running
Mongoose connected to db...
Mongodb connected....

When i run the docker-compose up command and the server runs in the container i get this output

[nodemon] 2.0.15
docker-server  | [nodemon] to restart at any time, enter `rs`
docker-server  | [nodemon] watching path(s): *.*
docker-server  | [nodemon] watching extensions: js,mjs,json
docker-server  | [nodemon] starting `node index.js`
docker-server  | Works
docker-server  | Works
docker-server  | Mongoose connection is disconnected...

After a while the mongoose disconnects.

My package.json is

{
  "name": "make-me-a-sandwich",
  "version": "1.1.0",
  "description": "This is the Swagger 2.0 API for Web Architectures course group project work.        ",
  "main": "index.js",
  "scripts": {
    "prestart": "npm install",
    "start": "nodemon index.js"
  },
  "keywords": [
    "swagger"
  ],
  "license": "Unlicense",
  "private": true,
  "dependencies": {
    "connect": "^3.2.0",
    "js-yaml": "^3.3.0",
    "swagger-tools": "0.10.1",
    "mongoose": "^6.1.5",
    "nodemon": "^2.0.15"
}

}

My index.js file is

const http = require('http');
const connect = require('./models/db');

const PORT = 80;
const server = http.createServer(function (request, response) {

const { url, method, headers } = request;
const filePath = new URL(url, `http://${headers.host}`).pathname;

if (filePath === '/' && method.toUpperCase() === 'GET') {
    console.log("Works")
    response.statusCode = 200;
    response.setHeader('Content-Type', 'text/plain');
    response.end('Hello, World! GET\n');
} else {
    response.statusCode = 200;
    response.setHeader('Content-Type', 'text/plain');
    response.end('Hello, World! Teemu\n');
}

});

server.on('error', err => {
   console.error(err);
   server.close();
});

server.on('close', () => console.log('Server closed.'));

server.listen(PORT, () => {
    console.log("Server running");
});
connect.connectDB();

model/db.js

const mongoose = require('mongoose');

function connectDB() {
   mongoose
       .connect('mongodb://mongo_db:27017', {
           useNewUrlParser: true,
       })
       .then(() => {
           console.log('Mongodb connected....');
       })
       .catch(err => console.log(err.message));

   mongoose.connection.on('connected', () => {
       console.log('Mongoose connected to db...');
   });

   mongoose.connection.on('error', err => {
       console.log(err.message);
   });

   mongoose.connection.on('disconnected', () => {
       console.log('Mongoose connection is disconnected...');
   });
};
function disconnectDB() {
    mongoose.disconnect();
}

module.exports = { connectDB, disconnectDB };

Dockerfile

FROM node:17.3.0

WORKDIR /server

COPY package.json .

RUN npm install

COPY . .

EXPOSE 80

CMD ["npm", "start"]

docker-compose file

version: "3"

services:
  server-a:
    container_name: docker-server
    build:
      dockerfile: Dockerfile
      context:  ./backend/server-a
    ports:
      - "3000:80"
    links: 
      - mongo_db
    networks:
      - backend
  mongo_db:
    container_name: mongo
    image: mongo:latest
    ports:
      - '27017:27017'
networks:
  backend:

Help would be really appreciated. Let me also know if i can offer any other information.

CodePudding user response：

Different containers need to be on the same Compose network to communicate. If a service doesn't have a networks: block, Compose automatically attaches it to a default network. So in your example, the server-a container is only on the backend network, but the mongo_db container is only on the default network, and that's why they can't communicate.

The easiest way to resolve this is to delete all of the networks: blocks in the file. Then Compose will attach all of the containers to the default network. Removing other unnecessary options, you could reduce this Compose file to just

version: "3.8"
services:
  server-a:
    build: ./backend/server-a
    ports:
      - "3000:80"
  mongo_db:
    image: mongo:latest
    ports:
      - '27017:27017'

In a comment you suggest that it's important to keep a second named network. If that's the case, then you need to make sure the database container also has a networks: block that names a network in common with the application container.