Docker Compose for Node.js and MongoDB: Setup Guide

Use a docker-compose.yml file to define services for node.js and mongodb. This file sets up MongoDB as a database service and Node.js as an app service that connects to it, making it easy to run both with one command.

Syntax

A docker-compose.yml file defines multiple services that run together. Each service has a name and configuration like the image to use, ports to expose, environment variables, and volumes for data.

Key parts:

• version: Docker Compose file format version.
• services: List of containers to run.
• image: Docker image to use for the service.
• ports: Map container ports to host ports.
• environment: Set environment variables inside the container.
• volumes: Persist data or share files between host and container.

yaml

version: '3.8'
services:
  service_name:
    image: image_name:tag
    ports:
      - "host_port:container_port"
    environment:
      - ENV_VAR=value
    volumes:
      - host_path:container_path

Example

This example shows a docker-compose.yml file that runs MongoDB and a Node.js app. MongoDB stores data, and Node.js connects to it using the service name mongodb as the database host.

yaml

version: '3.8'

services:
  mongodb:
    image: mongo:6.0
    restart: always
    ports:
      - "27017:27017"
    volumes:
      - mongo-data:/data/db

  nodeapp:
    build: ./nodeapp
    ports:
      - "3000:3000"
    environment:
      - MONGO_URL=mongodb://mongodb:27017/mydatabase
    depends_on:
      - mongodb

volumes:
  mongo-data:

Output

Starting mongodb ... done
Starting nodeapp ... done

# Node.js app listens on port 3000 and connects to MongoDB at mongodb:27017

Common Pitfalls

• Wrong MongoDB host: Using localhost inside Node.js container won't work; use the MongoDB service name mongodb instead.
• Missing depends_on: Node.js might start before MongoDB is ready; use depends_on to start MongoDB first.
• Data loss: Not using volumes for MongoDB causes data to be lost when container stops.
• Port conflicts: Make sure host ports (like 27017 or 3000) are free before running.

yaml

Wrong example:

services:
  nodeapp:
    environment:
      - MONGO_URL=mongodb://localhost:27017/mydatabase

Right example:

services:
  nodeapp:
    environment:
      - MONGO_URL=mongodb://mongodb:27017/mydatabase
    depends_on:
      - mongodb

Quick Reference

Remember these tips when using Docker Compose with Node.js and MongoDB:

• Use service names as hostnames to connect containers.
• Use volumes to keep MongoDB data safe.
• Use depends_on to control startup order.
• Expose ports to access services from your machine.

Key Takeaways

Define Node.js and MongoDB as services in a single docker-compose.yml file.

Use the MongoDB service name as the database host inside Node.js environment variables.

Add volumes to MongoDB service to persist data across container restarts.

Use depends_on to ensure MongoDB starts before Node.js app.

Map ports to access Node.js app and MongoDB from your host machine.