Docker Executor

Run workflow steps in Docker containers for isolated, reproducible execution.

Basic Usage

steps:
  - name: hello
    executor:
      type: docker
      config:
        image: alpine
        autoRemove: true
    command: echo "hello from container"

Execute in Existing Container

steps:
  - name: exec-in-running
    executor:
      type: docker
      config:
        containerName: my-app
        exec:
          user: root
          workingDir: /app
    command: ./maintenance.sh

Configuration Options

Image Management

executor:
  type: docker
  config:
    image: python:3.13
    pull: always        # always, missing, never
    platform: linux/amd64
    autoRemove: true

Volume Mounts

executor:
  type: docker
  config:
    image: node:22
    host:
      binds:
        - /host/data:/container/data:ro # Read-only
        - ${PWD}/app:/app               # Current directory

Environment Variables

executor:
  type: docker
  config:
    image: postgres:17
    container:
      env:
        - POSTGRES_PASSWORD=secret
        - POSTGRES_USER=admin
        - DEBUG=${DEBUG}  # From host

Working Directory

executor:
  type: docker
  config:
    image: maven:3
    container:
      workingDir: /project
    host:
      binds:
        - ./:/project

Resource Limits

executor:
  type: docker
  config:
    image: stress
    host:
      memory: 536870912  # 512MB
      cpuShares: 512

Real-World Examples

Data Processing Pipeline

steps:
  - name: extract
    executor:
      type: docker
      config:
        image: python:3.13-slim
        autoRemove: true
        host:
          binds:
            - ./data:/data
    command: python extract.py /data/raw.csv

  - name: transform
    executor:
      type: docker
      config:
        image: apache/spark:3.5.6
        autoRemove: true
        host:
          binds:
            - ./data:/data
          memory: 2147483648  # 2GB
    command: spark-submit transform.py

  - name: load
    executor:
      type: docker
      config:
        image: postgres:17
        autoRemove: true
        container:
          env:
            - PGPASSWORD=${DB_PASSWORD}
    command: psql -h db -U user -f load.sql

Build and Deploy

steps:
  - name: build
    executor:
      type: docker
      config:
        image: golang:1.24
        autoRemove: true
        host:
          binds:
            - .:/app
        container:
          workingDir: /app
          env:
            - CGO_ENABLED=0
    command: go build -o server .

  - name: test
    executor:
      type: docker
      config:
        image: golang:1.24
        autoRemove: true
        host:
          binds:
            - .:/app
        container:
          workingDir: /app
    command: go test ./...

  - name: package
    executor:
      type: docker
      config:
        image: docker:latest
        autoRemove: true
        host:
          binds:
            - /var/run/docker.sock:/var/run/docker.sock
            - .:/workspace
    command: docker build -t myapp:${VERSION} /workspace

Database Operations

steps:
  - name: backup
    executor:
      type: docker
      config:
        image: mysql:9.4
        autoRemove: true
        container:
          env:
            - MYSQL_PWD=${DB_PASSWORD}
        host:
          binds:
            - ./backups:/backups
    command: |
      mysqldump -h db.example.com -u root \
        --all-databases --single-transaction \
        > /backups/backup-$(date +%Y%m%d).sql

  - name: compress
    executor:
      type: docker
      config:
        image: alpine
        autoRemove: true
        host:
          binds:
            - ./backups:/backups
    command: gzip /backups/backup-*.sql

Docker in Docker

Using Host Docker Socket

steps:
  - name: docker-operations
    executor:
      type: docker
      config:
        image: docker:latest
        autoRemove: true
        host:
          binds:
            - /var/run/docker.sock:/var/run/docker.sock
    command: docker ps

Docker Compose Setup

# compose.yml for Dagu with Docker support
services:
  dagu:
    image: ghcr.io/dagu-org/dagu:latest
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - ./dags:/var/lib/dagu/dags
    user: "0:0"  # Run as root for Docker access

Advanced Patterns

Multi-Stage Processing

steps:
  - name: compile
    executor:
      type: docker
      config:
        image: rust:1.88
        autoRemove: true
        host:
          binds:
            - ./src:/src
            - ./target:/target
    command: cargo build --release

  - name: package
    executor:
      type: docker
      config:
        image: alpine
        autoRemove: true
        host:
          binds:
            - ./target/release:/app
    command: tar -czf app.tar.gz /app

Platform-Specific Builds

steps:
  - name: build-amd64
    executor:
      type: docker
      config:
        image: golang:1.24
        platform: linux/amd64
        autoRemove: true
    command: GOARCH=amd64 go build

  - name: build-arm64
    executor:
      type: docker
      config:
        image: golang:1.24
        platform: linux/arm64
        autoRemove: true
    command: GOARCH=arm64 go build

Error Handling

Continue on Specific Exit Codes

steps:
  - name: check-data
    executor:
      type: docker
      config:
        image: alpine
        autoRemove: true
    command: test -f /data/input.csv
    continueOn:
      exitCode: [1]  # File not found is OK

  - name: process-if-exists
    executor:
      type: docker
      config:
        image: python:3.13
        autoRemove: true
    command: python process.py || echo "No data to process"

Performance Tips

1. Use specific tags instead of latest for reproducibility
2. Set pull: missing to use cached images
3. Remove containers with autoRemove: true
4. Mount only necessary directories to minimize overhead
5. Use multi-stage builds for smaller final images

Security Considerations

• Docker socket access grants full control over host Docker
• Run as non-root when possible using container.user
• Use read-only mounts for input data
• Avoid mounting sensitive host directories
• Set resource limits to prevent resource exhaustion

See Also

• Shell Executor - Run commands directly
• SSH Executor - Execute on remote hosts
• Execution Control - Advanced patterns