Creating Dockerized Microservices

What Does It Mean to Dockerize a Microservice?

Dockerizing a service involves creating a Docker image that contains everything the service needs to run:

• Source code
• Dependencies
• Runtime environment
• Configuration files

This image can then be used to create isolated, reproducible containers across development, testing, and production.

Writing Dockerfiles for Microservices

Let’s take a Node.js-based user-service as an example:

# Use a lightweight Node.js image
FROM node:18-alpine

# Set the working directory inside the container
WORKDIR /app

# Copy dependency files first (for better layer caching)
COPY package*.json ./

# Install only production dependencies
RUN npm install --only=production

# Copy application source code
COPY . .

# Expose the service's port
EXPOSE 5000

# Run the service
CMD ["node", "server.js"]

This Dockerfile ensures small image size and fast builds by using caching effectively and limiting unnecessary files.

Building & Running the Service in a Container

To build the Docker image and run it as a container:

// Build the image and name it user-service
docker build -t user-service .

// Run the container in detached mode on port 5000
docker run -d -p 5000:5000 user-service

The -p flag maps the container's internal port to your host system so you can access the service via http://localhost:5000.

Dockerizing Multiple Microservices

Here’s an example setup for a small e-commerce system:

microservices-app/
├── user-service/
│   ├── Dockerfile
│   ├── server.js
│   └── package.json
├── order-service/
│   ├── Dockerfile
│   ├── server.js
│   └── package.json
├── product-service/
│   ├── Dockerfile
│   ├── server.js
│   └── package.json

Each service lives in its own directory with its own configuration and dependencies.

Best Practices

• Keep Dockerfiles minimal and clean
• Use multi-stage builds if needed (e.g., for Go or Java apps)
• Use .dockerignore to prevent unnecessary files from being copied
• Use environment variables for configuration, not hardcoded values

Example: .dockerignore

Helps reduce image size and build time:

node_modules
npm-debug.log
Dockerfile
.dockerignore

With each microservice Dockerized, you're ready to run them together using Docker Compose, manage shared resources, and prepare for inter-service communication.