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Deno and Docker

Using Deno with Docker Jump to heading

Deno provides official Docker files and images.

To use the official image, create a Dockerfile in your project directory:

FROM denoland/deno:latest

# Create working directory
WORKDIR /app

# Copy source
COPY . .

# Compile the main app
RUN deno cache main.ts

# Run the app
CMD ["deno", "run", "--allow-net", "main.ts"]

Best Practices Jump to heading

Use Multi-stage Builds Jump to heading

For smaller production images:

# Build stage
FROM denoland/deno:latest AS builder
WORKDIR /app
COPY . .
RUN deno cache main.ts

# Production stage
FROM denoland/deno:latest
WORKDIR /app
COPY --from=builder /app .
CMD ["deno", "run", "--allow-net", "main.ts"]

Permission Flags Jump to heading

Specify required permissions explicitly:

CMD ["deno", "run", "--allow-net=api.example.com", "--allow-read=/data", "main.ts"]

Development Container Jump to heading

For development with hot-reload:

FROM denoland/deno:latest

WORKDIR /app
COPY . .

CMD ["deno", "run", "--watch", "--allow-net", "main.ts"]

Common Issues and Solutions Jump to heading

  1. Permission Denied Errors

    • Use --allow-* flags appropriately
    • Consider using deno.json permissions

  2. Large Image Sizes

    • Use multi-stage builds
    • Include only necessary files
    • Add proper .dockerignore

  3. Cache Invalidation

    • Separate dependency caching
    • Use proper layer ordering

Example .dockerignore Jump to heading

.git
.gitignore
Dockerfile
README.md
*.log
_build/
node_modules/

Available Docker Tags Jump to heading

Deno provides several official tags:

  • denoland/deno:latest - Latest stable release
  • denoland/deno:alpine - Alpine-based smaller image
  • denoland/deno:distroless - Google's distroless-based image
  • denoland/deno:ubuntu - Ubuntu-based image
  • denoland/deno:1.x - Specific version tags

Environment Variables Jump to heading

Common environment variables for Deno in Docker:

ENV DENO_DIR=/deno-dir/
ENV DENO_INSTALL_ROOT=/usr/local
ENV PATH=${DENO_INSTALL_ROOT}/bin:${PATH}

# Optional environment variables
ENV DENO_NO_UPDATE_CHECK=1
ENV DENO_NO_PROMPT=1

Running Tests in Docker Jump to heading

FROM denoland/deno:latest

WORKDIR /app
COPY . .

# Run tests
CMD ["deno", "test", "--allow-none"]

Using Docker Compose Jump to heading

// filepath: docker-compose.yml
version: "3.8"
services:
  deno-app:
    build: .
    volumes:
      - .:/app
    ports:
      - "8000:8000"
    environment:
      - DENO_ENV=development
    command: ["deno", "run", "--watch", "--allow-net", "main.ts"]

Health Checks Jump to heading

HEALTHCHECK --interval=30s --timeout=3s \
  CMD deno eval "try { await fetch('http://localhost:8000/health'); } catch { Deno.exit(1); }"

Common Development Workflow Jump to heading

For local development:

  1. Build the image: docker build -t my-deno-app .
  2. Run with volume mount:
docker run -it --rm \
  -v ${PWD}:/app \
  -p 8000:8000 \
  my-deno-app

Security Considerations Jump to heading

  • Run as non-root user:
# Create deno user
RUN addgroup --system deno && \
    adduser --system --ingroup deno deno

# Switch to deno user
USER deno

# Continue with rest of Dockerfile
  • Use minimal permissions:
CMD ["deno", "run", "--allow-net=api.example.com", "--allow-read=/app", "main.ts"]
  • Consider using --deny-* flags for additional security

Working with Workspaces in Docker Jump to heading

When working with Deno workspaces (monorepos) in Docker, there are two main approaches:

1. Full Workspace Containerization Jump to heading

Include the entire workspace when you need all dependencies:

FROM denoland/deno:latest

WORKDIR /app

# Copy entire workspace
COPY deno.json .
COPY project-a/ ./project-a/
COPY project-b/ ./project-b/

WORKDIR /app/project-a
CMD ["deno", "run", "-A", "mod.ts"]

2. Minimal Workspace Containerization Jump to heading

For smaller images, include only required workspace members:

  1. Create a build context structure:
project-root/
├── docker/
│   └── project-a/
│       ├── Dockerfile
│       ├── .dockerignore
│       └── build-context.sh
├── deno.json
├── project-a/
└── project-b/
  1. Create a .dockerignore:
// filepath: docker/project-a/.dockerignore
*
!deno.json
!project-a/**
!project-b/**  # Only if needed
  1. Create a build context script:
// filepath: docker/project-a/build-context.sh
#!/bin/bash

# Create temporary build context
BUILD_DIR="./tmp-build-context"
mkdir -p $BUILD_DIR

# Copy workspace configuration
cp ../../deno.json $BUILD_DIR/

# Copy main project
cp -r ../../project-a $BUILD_DIR/

# Copy only required dependencies
if grep -q "\"@scope/project-b\"" "../../project-a/mod.ts"; then
    cp -r ../../project-b $BUILD_DIR/
fi
  1. Create a minimal Dockerfile:
// filepath: docker/project-a/Dockerfile
FROM denoland/deno:latest

WORKDIR /app

# Copy only necessary files
COPY deno.json .
COPY project-a/ ./project-a/
# Copy dependencies only if required
COPY project-b/ ./project-b/

WORKDIR /app/project-a

CMD ["deno", "run", "-A", "mod.ts"]
  1. Build the container:
cd docker/project-a
./build-context.sh
docker build -t project-a -f Dockerfile tmp-build-context
rm -rf tmp-build-context

Best Practices Jump to heading

  • Always include the root deno.json file
  • Maintain the same directory structure as development
  • Document workspace dependencies clearly
  • Use build scripts to manage context
  • Include only required workspace members
  • Update .dockerignore when dependencies change

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