Internal Docker Standards

This document outlines the mandatory standards and best practices for containerizing applications within our organization. These guidelines ensure consistency, security, and performance across all projects.

1. Project Initialization & Structure

Every project must be containerized. The root of the repository must contain the necessary configuration to build and run the application independently.

File Requirements

Dockerfile: Defines the build process.

.dockerignore: Excludes unnecessary files from the build context.

docker-compose.yml: Defines the production/integration infrastructure.

docker-compose.dev.yml: Defines the local development environment.

The .dockerignore File

To optimize build speed and security, you must exclude all files not required for the application runtime. This prevents secrets (.env) and local build artifacts (node_modules) from accidentally entering the image.

Standard Exclusion List

.git
.vscode
.editorconfig
.env
README.md
Dockerfile
docker-compose*.yml
node_modules
.venv
__pycache__
.pytest_cache
.nuxt
dist

2. Dockerfile Development

Base Images & Tagging

No latest tags: Never depend on the latest tag. It is mutable and leads to non-reproducible builds.
Pin Versions: Use specific version tags (e.g., node:24-alpine or python:3.13-alpine).
For Web Applications which are sperated in Frontend and Backend services, ensure compatibility when the Major and Minor version are the same. Patch versions can differ. So for example 1.3.1 and 1.3.5 are compatible, but 1.2.x and 1.3.x are not.
Minimal Base Images: Prefer alpine or slim (only if alpine fails) variants to reduce image size and download time.

Multi-Stage Builds

Use multi-stage builds to separate build dependencies (compilers, headers, full CLI tools) from runtime dependencies.

Build Layer: Compiles code, installs dependencies, builds assets.
Run Layer: Copies only the artifacts from the Build Layer.

Security Context

Rootless Execution: Containers should not run as root. Create a specific user or use the default non-root user provided by the base image (e.g., node user in Node images).
Privileged Mode: Do not run containers in --privileged mode.
Kubernetes pod security standards prohibit "run as root" containers.

Nuxt Layer Configuration with Build Arguments

When building Nuxt applications that use our Nuxt Layers, some layers require environment variables that specify which implementation to use (e.g., AUTH_LAYER_URI, LOGGER_LAYER_URI). These variables are resolved at build time during nuxt build, not at runtime.

Important

Layer URI environment variables must be passed as Docker build arguments (ARG), not runtime environment variables. If you only set them at runtime, the layer will already be compiled with the wrong (or missing) implementation.

Required Build Arguments for Nuxt Layers

Build Argument	Description	Example Value
`AUTH_LAYER_URI`	Authentication implementation layer	`github:DCC-BS/nuxt-layers/azure-auth`
`LOGGER_LAYER_URI`	Logger implementation layer	`github:DCC-BS/nuxt-layers/pino-logger`

Dockerfile Pattern

Add these lines to your Nuxt Dockerfile after FROM and before the build step:

dockerfile

# Define build arguments (available as env vars during RUN commands)
ARG AUTH_LAYER_URI
ARG LOGGER_LAYER_URI

# ... then run the build (ARGs are injected into the shell environment)
RUN bun x nuxi build

No ENV Needed

Docker injects ARG values into the shell environment during RUN commands. There's no need to duplicate them with ENV — the values are available to nuxt build via process.env and won't persist into the final image.

Building the Image

Pass the values using --build-arg:

bash

docker build \
  --build-arg AUTH_LAYER_URI=github:DCC-BS/nuxt-layers/azure-auth \
  --build-arg LOGGER_LAYER_URI=github:DCC-BS/nuxt-layers/pino-logger \
  -t my-nuxt-app:latest .

Docker Compose Configuration

In your docker-compose.yml or docker/services.compose.yml:

yaml

services:
  app-frontend:
    build:
      context: .
      dockerfile: Dockerfile
      args:
        AUTH_LAYER_URI: ${AUTH_LAYER_URI:-github:DCC-BS/nuxt-layers/no-auth}
        LOGGER_LAYER_URI: ${LOGGER_LAYER_URI:-github:DCC-BS/nuxt-layers/pino-logger}

Then create a .env file with your desired values or set them in your shell before running docker compose build.

Key Differences: ARG vs ENV

Aspect	ARG (Build Argument)	ENV (Environment Variable)
Available during	`RUN` commands in build stage	Build and runtime
Accessible to processes	✅ Injected into shell env during `RUN`	✅ Always in `process.env`
Set via	`--build-arg` flag	`-e` flag, `environment:` in compose, or `ENV` instruction
Persisted in image	❌ No	✅ Yes
Use for Layer URIs	✅ Yes (build-time only, not persisted)	❌ Unnecessary duplication

Full Documentation

For comprehensive documentation on Nuxt layer configuration and all available layers, see Nuxt Layers - Environment Configuration in Docker.

Examples

Node.js / Nuxt (Bun)

dockerfile

# Stage 1: Build
FROM node:24-alpine AS build

# Install Bun
RUN npm install -g bun

WORKDIR /app

# Build arguments for Nuxt layer configuration (see section above)
ARG AUTH_LAYER_URI
ARG LOGGER_LAYER_URI

# Dependency caching layer
COPY package.json bun.lock ./
RUN bun install --frozen-lockfile

# Build layer - ARGs are injected as env vars, Nuxt reads via process.env
COPY . .
RUN bun x nuxi prepare
RUN bun x nuxi build

# Stage 2: Runtime (ARGs not needed - layers compiled into .output)
FROM node:24-alpine

WORKDIR /app

# Security: Set non-root user
USER node

# Copy artifacts
COPY --from=build --chown=node:node /app/.output ./

EXPOSE 3000
ENV NODE_ENV=production

ENTRYPOINT ["node", "./server/index.mjs"]

Python (Alpine)

# Stage 1: Builder
FROM python:3.13-alpine as builder
COPY --from=ghcr.io/astral-sh/uv:latest /uv /uvx /bin/

WORKDIR /app

ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1
ENV UV_COMPILE_BYTECODE=1
ENV UV_LINK_MODE=copy

# Install build dependencies
RUN apk add --no-cache gcc musl-dev

# Copy dependency files
COPY pyproject.toml uv.lock ./

# Install dependencies
# --locked: Sync with lockfile
# --no-dev: Exclude development dependencies
# --no-install-project: Install dependencies only (caching layer)
RUN --mount=type=cache,target=/root/.cache/uv \
    uv sync --locked --no-dev --no-install-project --no-editable

# Copy application code
COPY . /app

# Sync project
RUN --mount=type=cache,target=/root/.cache/uv \
    uv sync --locked --no-dev --no-editable

# Stage 2: Runtime
FROM python:3.13-alpine

WORKDIR /app

# Create non-root user (Alpine syntax)
RUN addgroup -S app && adduser -S app -G app

# Copy the environment, but not the source code
COPY --from=builder --chown=app:app /app/.venv /app/.venv

# Copy application code
COPY . /app

# Enable virtual environment
ENV PATH="/app/.venv/bin:$PATH"

RUN chown -R app:app /app

USER app

CMD ["uv", "run", "main"]

3. Orchestration & Composition

We utilize a modular Docker Compose strategy to avoid duplication between development and production configurations.

The "Extends" Pattern

docker/services.compose.yml: The base definition. Contains image names, build contexts, and shared environment variables.
docker-compose.dev.yml: Extends the base. Adds hot-reloading (volumes), debugging ports, and local overrides.
docker-compose.yml: Extends the base. Defines production networks, restart policies, and resource limits.

Example Directory Structure

project-root/
├── docker/
│   └── services.compose.yml
│   └── .env.backend
│   └── nginx.conf
├── Dockerfile
├── .dockerignore
├── docker-compose.dev.yml
├── docker-compose.yml

Syntax Reference

# docker-compose.dev.yml
services:
  app-backend:
    extends:
      file: ./docker/services.compose.yml
      service: app-backend
    environment:
      - DEBUG=true
    ports:
      - "8000:8000"
  llm:
    extends:
      file: ./docker/services.compose.yml
      service: llm

# docker-compose.yml
networks:
  app-network:
    driver: bridge

services:
  nginx:
    extends:
      file: ./docker/services.compose.yml
      service: nginx
    depends_on:
      - app-frontend
    networks:
      - app-network

  llm:
    extends:
      file: ./docker/services.compose.yml
      service: llm
    networks:
      - app-network

  app-backend:
    extends:
      file: ./docker/services.compose.yml
      service: app-backend
    networks:
      - app-network

  app-frontend:
    extends:
      file: ./docker/services.compose.yml
      service: app-frontend
    networks:
      - app-network

# docker/services.compose.yml
services:
  nginx:
    image: nginx:alpine
    ports:
      - '8090:80'
      - '8443:443'
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
  llm:
    platform: linux/amd64
    image: vllm/vllm-openai:v0.11.2
    container_name: llm
    expose:
      - "8000"
    env_file: ".env.backend"
    runtime: nvidia
    deploy:
      resources:
        reservations:
          devices:
            - driver: nvidia
              count: all
              capabilities: [ gpu ]
    ipc: host
    volumes:
      - ~/.cache/huggingface:/root/.cache/huggingface
    command: >
      Qwen/Qwen3-32B-AWQ
      --port 8000
      --max-model-len 10000
      --max-num-seqs 1
      --kv-cache-dtype fp8
      --gpu-memory-utilization 0.95
      --enable-auto-tool-choice
      --tool-call-parser hermes
      --tensor-parallel-size 1
      --reasoning-parser qwen3
      --uvicorn-log-level warning
      --disable-log-requests
  app-backend:
    image: ghcr.io/dcc-bs/app-backend:latest
    expose:
     - "8000"
    env_file:
     - .env.backend
  app-frontend:
    container_name: app-frontend
    build:
      context: .
      dockerfile: ../Dockerfile
    env_file: "../.env"
    environment:
      - NUXT_API_URL=http://app-backend:8000
      - PORT=3000
    expose:
      - 3000

# nginx.conf
events {
    worker_connections 1024;
}

http {
    # Increase buffer sizes for large headers/cookies
    client_header_buffer_size 16k;
    large_client_header_buffers 4 16k;
    client_max_body_size 50M;
    
    upstream app-frontend {
        server app-frontend:3000;
    }

    upstream app-backend {
        server app-backend:8000;
    }

    # Frontend proxy
    server {
        listen 80;
        server_name localhost;

        # Proxy frontend
        location / {
            proxy_pass http://app-frontend;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            
            # WebSocket support
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
            
            # Increase proxy buffer sizes for large headers
            proxy_buffer_size 16k;
            proxy_buffers 4 16k;
            proxy_busy_buffers_size 16k;
        }

        # Proxy backend API (with fallback for when backend is down)
        location /backend/ {
            proxy_pass http://app-backend/;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            
            # Handle backend unavailable gracefully
            proxy_connect_timeout 2s;
            proxy_send_timeout 2s;
            proxy_read_timeout 2s;
            
            # Return 503 if backend is unavailable
            error_page 502 503 504 = @backend_unavailable;
        }
        
        location @backend_unavailable {
            default_type application/json;
            return 503 '{"error": "Backend service is currently unavailable"}';
        }
    }
}

4. Quality Assurance & Optimization

Static Analysis & Linting

SonarQube: Ensure Dockerfiles are scanned during the CI process to detect security smells (e.g., hardcoded secrets, sudo usage).
Hadolint: Recommended for local linting of Dockerfile syntax.

Installation

Windows: scoop install hadolint
Ubuntu:

sudo wget -qO /usr/local/bin/hadolint https://github.com/hadolint/hadolint/releases/latest/download/hadolint-Linux-x86_64

sudo chmod a+x /usr/local/bin/hadolint

Usage

Local CLI: hadolint Dockerfile

Image Optimization

Size Analysis: Use Dive to inspect image layers and identify wasted space.
Layer Caching: Leverage the build cache by ordering instructions from stable to volatile. Copy dependency definitions (e.g., package.json) and install packages before copying the source code to avoid re-installing dependencies on every code change.
Clean Artifacts: Clear package manager caches (e.g., apk cache clean, rm -rf /var/lib/apt/lists/*) within the same RUN instruction as the installation to prevent temporary files from committing to the layer.
Further Reading: Guide to Reducing Docker Image Size

5. Deployment & CI/CD

Registry

Images are pushed to GHCR (GitHub Container Registry).
Namespace convention: ghcr.io/dcc-bs/<service-name>.

Versioning Strategy

Development: Tag with the branch name or dev.
Staging/Production: Tag with the Git Commit SHA (sha-xyz123) and the Semantic Version (v1.0.0).
Avoid Overwriting: Do not overwrite stable tags.

CI Workflow

Checkout Code.
Lint Dockerfile (Hadolint/SonarQube).
Build Image (using BuildKit).
Run Tests against the container.
Push to GHCR.

6. Docker Configuration (Host)

Rootless Daemon: Run the Docker daemon in rootless mode to mitigate privilege escalation vulnerabilities on the host machine.
Resource Limits: Configure global resource quotas to prevent a single container from exhausting host memory or CPU.

Composables

Components

Internal Docker Standards

1. Project Initialization & Structure

File Requirements

The .dockerignore File

Standard Exclusion List

2. Dockerfile Development

Base Images & Tagging

Multi-Stage Builds

Security Context

Nuxt Layer Configuration with Build Arguments

Required Build Arguments for Nuxt Layers

Dockerfile Pattern

Building the Image

Docker Compose Configuration

Key Differences: ARG vs ENV

Examples

Node.js / Nuxt (Bun)

Python (Alpine)

3. Orchestration & Composition

The "Extends" Pattern

Example Directory Structure

Syntax Reference

4. Quality Assurance & Optimization

Static Analysis & Linting

Installation

Usage

Image Optimization

5. Deployment & CI/CD

Registry

Versioning Strategy

CI Workflow

6. Docker Configuration (Host)

Internal Docker Standards ​

1. Project Initialization & Structure ​

File Requirements ​

The .dockerignore File ​

Standard Exclusion List ​

2. Dockerfile Development ​

Base Images & Tagging ​

Multi-Stage Builds ​

Security Context ​

Nuxt Layer Configuration with Build Arguments ​

Required Build Arguments for Nuxt Layers ​

Dockerfile Pattern ​

Building the Image ​

Docker Compose Configuration ​

Key Differences: ARG vs ENV ​

Examples ​

Node.js / Nuxt (Bun) ​

Python (Alpine) ​

3. Orchestration & Composition ​

The "Extends" Pattern ​

Example Directory Structure ​

Syntax Reference ​

4. Quality Assurance & Optimization ​

Static Analysis & Linting ​

Installation ​

Usage ​

Image Optimization ​

5. Deployment & CI/CD ​

Registry ​

Versioning Strategy ​

CI Workflow ​

6. Docker Configuration (Host) ​

Internal Docker Standards

1. Project Initialization & Structure

File Requirements

The .dockerignore File

Standard Exclusion List

2. Dockerfile Development

Base Images & Tagging

Multi-Stage Builds

Security Context

Nuxt Layer Configuration with Build Arguments

Required Build Arguments for Nuxt Layers

Dockerfile Pattern

Building the Image

Docker Compose Configuration

Key Differences: ARG vs ENV

Examples

Node.js / Nuxt (Bun)

Python (Alpine)

3. Orchestration & Composition

The "Extends" Pattern

Example Directory Structure

Syntax Reference

4. Quality Assurance & Optimization

Static Analysis & Linting

Installation

Usage

Image Optimization

5. Deployment & CI/CD

Registry

Versioning Strategy

CI Workflow

6. Docker Configuration (Host)