DevContainers: Big and Bold or Small and Smart?

Recently, I was deep into a project juggling multiple technologies—think of it like trying to cook a gourmet meal with ingredients from five different cuisines. Then, the ultimate question from the customer dropped:

👉 "Should we go with one mega DevContainer to rule them all or split things up into individual containers?"

It sounded simple at first, but as I dove into the details, it became one of those "hold my coffee, let me investigate" moments. After some hands-on exploration, here’s what I found—and it might just save you some dev-time headaches too!

When dealing with a solution containing multiple technologies like React with TypeScript, .NET 9, and Java, the best approach to organizing your Dev Containers depends on your team setup, project requirements, and the level of independence needed for each component.

Options: Single vs. Multiple Dev Containers

Option 1: Single Dev Container

A single Dev Container includes everything needed for all technologies.

Pros:

• Unified environment: All team members have the same tools and dependencies.
• Simplified setup: Only one container to manage.
• Seamless cross-component testing: Easier to run React, .NET, and Java services together for integration testing.

Cons:

• Larger image size: The container might become bloated with unnecessary dependencies.
• Complex configuration: Combining dependencies for multiple runtimes (Node.js, .NET, Java) in one container can be tricky.
• Overhead for non-full-stack devs: Developers focusing on only one part (e.g., frontend) might have unnecessary tools installed.

Recommended When:

• All team members need to work across all components.
• Your projects are tightly coupled and require frequent integration.

Example devcontainer.json (Single Dev Container):

{
  "name": "Full Stack Environment",
  "build": {
    "dockerfile": "Dockerfile"
  },
  "settings": {
    "terminal.integrated.defaultProfile.linux": "bash"
  },
  "extensions": [
    "dbaeumer.vscode-eslint",
    "ms-dotnettools.csharp",
    "redhat.java",
    "esbenp.prettier-vscode"
  ],
  "postCreateCommand": "npm install && dotnet restore && ./gradlew build"
}

Example Dockerfile:

# Base image with Node.js, .NET 9 SDK, and Java 17
FROM mcr.microsoft.com/devcontainers/universal:2

# Install .NET 9 SDK
RUN apt-get update && apt-get install -y dotnet-sdk-9.0

# Install Java (default: OpenJDK 17)
RUN apt-get update && apt-get install -y openjdk-17-jdk

# Set up default work directory
WORKDIR /workspaces/project

Option 2: Multiple Dev Containers

Create separate Dev Containers for each component (React, .NET, Java) and allow developers to work on individual parts independently.

Pros:

• Optimized environments: Each container is lightweight and focused on its technology stack.
• Modular development: Frontend and backend developers can work independently.
• Easier maintenance: Updates and changes to dependencies are isolated.

Cons:

• More setup time: Multiple Dev Containers require more configuration.
• Cross-component challenges: Running and testing the entire system requires additional steps (e.g., Docker Compose).

Recommended When:

• Team members specialize in specific components (frontend vs. backend).
• Your projects are loosely coupled or use APIs to interact.
• Developers often work on just one part at a time.

*Example Setup (Multiple Dev Containers): *

Frontend (React + TypeScript) devcontainer.json:

{
  "name": "React TypeScript Environment",
  "image": "mcr.microsoft.com/devcontainers/javascript-node:16",
  "settings": {
    "terminal.integrated.defaultProfile.linux": "bash"
  },
  "extensions": [
    "dbaeumer.vscode-eslint",
    "esbenp.prettier-vscode"
  ],
  "postCreateCommand": "npm install"
}

Backend .NET (API) devcontainer.json:

{
  "name": ".NET 9 Environment",
  "image": "mcr.microsoft.com/devcontainers/dotnet:9.0",
  "settings": {
    "terminal.integrated.defaultProfile.linux": "bash"
  },
  "extensions": [
    "ms-dotnettools.csharp"
  ],
  "postCreateCommand": "dotnet restore"
}

Backend Java (API) devcontainer.json:

{
  "name": "Java Development Environment",
  "image": "mcr.microsoft.com/devcontainers/java:17",
  "settings": {
    "terminal.integrated.defaultProfile.linux": "bash"
  },
  "extensions": [
    "redhat.java",
    "vscjava.vscode-java-debug"
  ],
  "postCreateCommand": "./gradlew build"```


}

Best Practice for Cross-Component Development

If you choose multiple containers but need them to work together:

Use Docker Compose: Create a docker-compose.yml file to orchestrate containers for the React, .NET, and Java components.

version: '3.8'
services:
  frontend:
    build: ./frontend
    ports:
      - "3000:3000"
  backend-dotnet:
    build: ./backend-dotnet
    ports:
      - "5000:5000"
  backend-java:
    build: ./backend-java
    ports:
      - "8080:8080"

Important! - Enable Network Communication: Ensure each container can communicate over Docker's default bridge network.

Recommendation

• Start with Multiple Dev Containers: Unless your team works full-stack across all components, separate Dev Containers provide better modularity and efficiency.
• Use Docker Compose for Integration: Combine multiple containers during integration and testing phases.
• Document Everything: Clearly document the setup for each Dev Container and how to integrate them.