Debugging a NestJS application running inside a Docker container involves a few steps, but it's quite manageable. Here's a general guide along with an example:

  1. Enable Debugging in Your NestJS Application:

    • Ensure your NestJS application is configured to support debugging. You typically do this by setting up a debugging configuration in your package.json or tsconfig.json.

  2. Expose Debugging Ports:

    • When running your NestJS application inside a Docker container, you need to expose the debugging port to your host machine. This allows you to attach a debugger from your development environment.

  3. Update Dockerfile:

    • Modify your Dockerfile to include the necessary debugging configurations and expose the debugging port.

  4. Build Docker Image:

    • Build your Docker image with the updated Dockerfile.

  5. Run Docker Container:

    • Start your Docker container, ensuring that you map the exposed debugging port to a port on your host machine.

  6. Attach Debugger:

    • Finally, attach your debugger from your development environment to the debugging port on your host machine.

Here's an example of how you might update your NestJS application and Docker configuration:

1. Enable Debugging in Your NestJS Application

Add a debugging configuration in your package.json:

"scripts": {
  "start:debug": "nest start --debug --watch"
}

2. Update Dockerfile

# Use node:latest as base image
FROM node:latest

# Set working directory
WORKDIR /app

# Copy package.json and package-lock.json
COPY package*.json ./

# Install dependencies
RUN npm install

# Copy the rest of the application code
COPY . .

# Expose debugging port
EXPOSE 9229

# Command to run the application
CMD ["npm", "run", "start:debug"]

3. Build Docker Image

Build your Docker image:

docker build -t my-nest-app .

4. Run Docker Container

Run your Docker container, mapping the debugging port to a port on your host machine:

docker run -p 3000:3000 -p 9229:9229 my-nest-app

5. Attach Debugger

In your development environment (e.g., Visual Studio Code), attach your debugger to localhost:9229.

With these steps and configurations, you should be able to debug your NestJS application running inside a Docker container effectively.