YAML Specification

Overview

Dagu workflows are defined using YAML files. Each file represents a DAG (Directed Acyclic Graph) that describes your workflow steps and their relationships.

Basic Structure

# Workflow metadata
description: "What this workflow does"
tags: [production, etl]    # Optional: for organization

# Scheduling
schedule: "0 * * * *"      # Optional: cron expression

# Execution control
maxActiveRuns: 1           # Max concurrent runs
maxActiveSteps: 10         # Max parallel steps
timeoutSec: 3600           # Workflow timeout (seconds)

# Parameters
params:
  - KEY: default_value
  - ANOTHER_KEY: "${ENV_VAR}"

# Environment variables
env:
  - VAR_NAME: value
  - PATH: ${PATH}:/custom/path

# Workflow steps
steps:
  - name: step-name        # Optional
    command: echo "Hello"
    depends: previous-step # Optional

# Lifecycle handlers
handlerOn:
  success:
    command: notify-success.sh
  failure:
    command: cleanup-on-failure.sh

Root Fields

Metadata Fields

Field	Type	Description	Default
name	string	Workflow name	Filename without extension
description	string	Human-readable description	-
tags	array	Tags for categorization	[]
group	string	Group name for organization	-

Scheduling Fields

Field	Type	Description	Default
schedule	string/array	Cron expression(s)	-
skipIfSuccessful	boolean	Skip if already succeeded today	false
restartWaitSec	integer	Wait seconds before restart	0

Schedule Formats

# Single schedule
schedule: "0 2 * * *"

# Multiple schedules
schedule:
  - "0 9 * * MON-FRI"   # 9 AM weekdays
  - "0 14 * * SAT,SUN"  # 2 PM weekends

# With timezone
schedule: "CRON_TZ=America/New_York 0 9 * * *"

# Start/stop schedules
schedule:
  start:
    - "0 8 * * MON-FRI"   # Start at 8 AM
  stop:
    - "0 18 * * MON-FRI"  # Stop at 6 PM
  restart:
    - "0 12 * * MON-FRI"  # Restart at noon

Execution Control Fields

Field	Type	Description	Default
maxActiveRuns	integer	Max concurrent workflow runs (-1 = unlimited)	1
maxActiveSteps	integer	Max parallel steps	1
timeoutSec	integer	Workflow timeout in seconds	0 (no timeout)
delaySec	integer	Initial delay before start (seconds)	0
maxCleanUpTimeSec	integer	Max cleanup time (seconds)	300
preconditions	array	Workflow-level preconditions	-
runConfig	object	User interaction controls when starting DAG	-

Data Fields

Field	Type	Description	Default
params	array	Default parameters	[]
env	array	Environment variables	[]
dotenv	string/array	.env files to load	[".env"]
workingDir	string	Working directory for the DAG	Directory of DAG file
logDir	string	Custom log directory	System default
histRetentionDays	integer	History retention days	30
maxOutputSize	integer	Max output size per step (bytes)	1048576

Container Configuration

Field	Type	Description	Default
container	object	Default container configuration for all steps	-

container:
  image: python:3.11
  pullPolicy: missing      # always, missing, never
  env:
    - API_KEY=${API_KEY}
  volumes:
    - /data:/data:ro
  workingDir: /app
  platform: linux/amd64
  user: "1000:1000"
  ports:
    - "8080:8080"
  network: host
  startup: keepalive       # keepalive | entrypoint | command
  command: ["sh", "-c", "my-daemon"]   # when startup: command
  waitFor: running         # running | healthy
  logPattern: "Ready to accept connections"  # optional regex
  restartPolicy: unless-stopped              # optional: no|always|unless-stopped
  keepContainer: false     # Keep container after DAG run

Note: A DAG‑level container is started once and kept alive while the workflow runs; each step executes via docker exec inside that container. This means step commands do not pass through the image’s ENTRYPOINT/CMD. If your image’s entrypoint dispatches subcommands, invoke it explicitly in the step command (see Execution Model and Entrypoint Behavior). Readiness waiting (running/healthy and optional logPattern) times out after 120 seconds with a clear error including the last known state.

SSH Configuration

Field	Type	Description	Default
ssh	object	Default SSH configuration for all steps	-

ssh:
  user: deploy
  host: production.example.com
  port: "22"           # Optional, defaults to "22"
  key: ~/.ssh/id_rsa   # Optional, defaults to standard keys
  password: "${SSH_PASSWORD}" # Optional; prefer keys for security
  strictHostKey: true  # Optional, defaults to true for security
  knownHostFile: ~/.ssh/known_hosts  # Optional, defaults to ~/.ssh/known_hosts

When configured at the DAG level, all steps using SSH executor will inherit these settings:

# DAG-level SSH configuration
ssh:
  user: deploy
  host: app.example.com
  key: ~/.ssh/deploy_key

steps:
  # These steps inherit the DAG-level SSH configuration
  - systemctl status myapp
  - systemctl restart myapp
  
  # Step-level config overrides DAG-level
  - executor:
      type: ssh
      config:
        user: backup      # Override user
        host: db.example.com  # Override host
        key: ~/.ssh/backup_key  # Override key
    command: mysqldump mydb > backup.sql

Important Notes:

• SSH and container fields are mutually exclusive at the DAG level
• Step-level SSH configuration completely overrides DAG-level configuration (no partial overrides)
• Password authentication is supported but not recommended; prefer key-based auth
• Default SSH keys are tried if no key is specified: ~/.ssh/id_rsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ed25519, ~/.ssh/id_dsa

Working Directory and Volume Resolution

When using container volumes with relative paths, the paths are resolved relative to the DAG's workingDir:

# DAG with working directory and container volumes
workingDir: /app/project
container:
  image: python:3.11
  volumes:
    - ./data:/data        # Resolves to /app/project/data:/data
    - .:/workspace        # Resolves to /app/project:/workspace
    - /abs/path:/other   # Absolute paths are unchanged

steps:
  - python process.py

Working Directory Inheritance:

• Steps inherit workingDir from the DAG if not explicitly set
• Step-level workingDir overrides DAG-level workingDir
• Both dir and workingDir set the working directory (use one or the other)

# Example of workingDir inheritance
workingDir: /project          # DAG-level working directory

steps:
  - pwd                   # Outputs: /project
  - workingDir: /custom   # Override DAG workingDir
    command: pwd          # Outputs: /custom

Queue Configuration

Field	Type	Description	Default
queue	string	Queue name	-

OpenTelemetry Configuration

Field	Type	Description	Default
otel	object	OpenTelemetry tracing configuration	-

otel:
  enabled: true
  endpoint: "localhost:4317"  # OTLP gRPC endpoint
  headers:
    Authorization: "Bearer ${OTEL_TOKEN}"
  insecure: false
  timeout: 30s
  resource:
    service.name: "dagu-${DAG_NAME}"
    service.version: "1.0.0"
    deployment.environment: "${ENVIRONMENT}"

See OpenTelemetry Tracing for detailed configuration.

Notification Fields

Field	Type	Description	Default
mailOn	object	Email notification triggers	-
errorMail	object	Error email configuration	-
infoMail	object	Info email configuration	-
smtp	object	SMTP server configuration	-

mailOn:
  success: true
  failure: true
  
errorMail:
  from: [email protected]
  to: [email protected]  # Single recipient (string)
  # Or multiple recipients (array):
  # to:
  #   - [email protected]
  #   - [email protected]
  prefix: "[ALERT]"
  attachLogs: true
  
infoMail:
  from: [email protected]
  to: [email protected]  # Single recipient (string)
  # Or multiple recipients (array):
  # to:
  #   - [email protected]
  #   - [email protected]
  prefix: "[INFO]"
  attachLogs: false
  
smtp:
  host: smtp.gmail.com
  port: "587"
  username: [email protected]
  password: ${SMTP_PASSWORD}

Handler Fields

Field	Type	Description	Default
handlerOn	object	Lifecycle event handlers	-

handlerOn:
  success:
    command: echo "Workflow succeeded"
  failure:
    command: echo "Notifying failure"
  cancel:
    command: echo "Cleaning up"
  exit:
    command: echo "Always running"

RunConfig

The runConfig field allows you to control user interactions when starting DAG runs:

Field	Type	Description	Default
disableParamEdit	boolean	Prevent parameter editing when starting DAG	false
disableRunIdEdit	boolean	Prevent custom run ID input when starting DAG	false

Example usage:

# Prevent users from modifying parameters at runtime
runConfig:
  disableParamEdit: true
  disableRunIdEdit: false

params:
  - ENVIRONMENT: production  # Users cannot change this
  - VERSION: 1.0.0           # This is fixed

This is useful when:

• You want to enforce specific parameter values for production workflows
• You need consistent run IDs for tracking purposes
• You want to prevent accidental parameter changes

Step Fields

Each step in the steps array can have these fields:

Basic Fields

Field	Type	Description	Default
name	string	Step name (optional - auto-generated if not provided)	Auto-generated
command	string	Command to execute	-
script	string	Inline script (alternative to command)	-
run	string	Run another DAG	-
depends	string/array	Step dependencies	-

Step Definition Formats

Steps can be defined in multiple formats:

Standard Format

steps:
  - echo "Hello"

Shorthand String Format

steps:
  - echo "Hello"     # Equivalent to: {command: echo "Hello"}
  - ls -la          # Equivalent to: {command: ls -la}

Nested Array Format (Parallel Steps)

steps:
  - echo "Sequential step 1"
  - 
    - echo "Parallel step 2a"
    - echo "Parallel step 2b"
  - echo "Sequential step 3"

In the nested array format:

• Steps within a nested array run in parallel
• They automatically depend on the previous sequential step
• The next sequential step automatically depends on all parallel steps in the group
• Auto-generated names follow the pattern: parallel_{group}_{command}_{index}

Execution Fields

Field	Type	Description	Default
dir	string	Working directory	Current directory
workingDir	string	Working directory (alternative to dir, inherits from DAG)	DAG's workingDir
shell	string	Shell to use	System default
stdout	string	Redirect stdout to file	-
stderr	string	Redirect stderr to file	-
output	string	Capture output to variable	-
env	array/object	Step-specific environment variables (overrides DAG-level)	-
params	string	Parameters for sub-DAG	-

Parallel Execution

Field	Type	Description	Default
parallel	array	Items to process in parallel	-
maxConcurrent	integer	Max parallel executions	No limit

steps:
  - run: file-processor
    parallel:
      items: [file1.csv, file2.csv, file3.csv]
      maxConcurrent: 2
    params: "FILE=${ITEM}"

Conditional Execution

Field	Type	Description	Default
preconditions	array	Conditions to check before execution	-
continueOn	object	Continue workflow on certain conditions	-

ContinueOn Fields

Field	Type	Description	Default
failure	boolean	Continue execution when step fails	false
skipped	boolean	Continue when step is skipped due to preconditions	false
exitCode	array	List of exit codes that allow continuation	[]
output	array	List of stdout patterns that allow continuation (supports regex with re: prefix)	[]
markSuccess	boolean	Mark step as successful when continue conditions are met	false

steps:
  - command: echo "Deploying"
    preconditions:
      - condition: "${ENVIRONMENT}"
        expected: "production"
      - condition: "`git branch --show-current`"
        expected: "main"
    
  - command: echo "Running optional task"
    continueOn:
      failure: true
      skipped: true
      exitCode: [0, 1, 2]
      output: ["WARNING", "SKIP", "re:^INFO:.*"]
      markSuccess: true

See the Continue On Reference for detailed documentation.

Error Handling

Field	Type	Description	Default
retryPolicy	object	Retry configuration	-
repeatPolicy	object	Repeat configuration	-
mailOnError	boolean	Send email on error	false
signalOnStop	string	Signal to send on stop	SIGTERM

Retry Policy Fields

Field	Type	Description	Default
limit	integer	Maximum retry attempts	-
intervalSec	integer	Base interval between retries (seconds)	-
backoff	any	Exponential backoff multiplier. true = 2.0, or specify custom number > 1.0	-
maxIntervalSec	integer	Maximum interval between retries (seconds)	-
exitCode	array	Exit codes that trigger retry	All non-zero

Exponential Backoff: When backoff is set, intervals increase exponentially using the formula:
interval * (backoff ^ attemptCount)

Repeat Policy Fields

Field	Type	Description	Default
repeat	string	Repeat mode: "while" or "until"	-
intervalSec	integer	Base interval between repetitions (seconds)	-
backoff	any	Exponential backoff multiplier. true = 2.0, or specify custom number > 1.0	-
maxIntervalSec	integer	Maximum interval between repetitions (seconds)	-
limit	integer	Maximum number of executions	-
condition	string	Condition to evaluate	-
expected	string	Expected value/pattern	-
exitCode	array	Exit codes that trigger repeat	-

Repeat Modes:

• while: Repeats while the condition is true or exit code matches
• until: Repeats until the condition is true or exit code matches

Exponential Backoff: When backoff is set, intervals increase exponentially using the formula:
interval * (backoff ^ attemptCount)

steps:
  - command: curl https://api.example.com
    retryPolicy:
      limit: 3
      intervalSec: 30
      exitCode: [1, 255]  # Retry only on specific codes
      
  - command: curl https://api.example.com
    retryPolicy:
      limit: 5
      intervalSec: 2
      backoff: true        # Exponential backoff (2.0x multiplier)
      maxIntervalSec: 60   # Cap at 60 seconds
      exitCode: [429, 503] # Rate limit or unavailable
    
  - command: check-process.sh
    repeatPolicy:
      repeat: while        # Repeat WHILE process is running
      exitCode: [0]        # Exit code 0 means process found
      intervalSec: 60
      limit: 30
      
  - command: echo "Checking status"
    output: STATUS
    repeatPolicy:
      repeat: until        # Repeat UNTIL status is ready
      condition: "${STATUS}"
      expected: "ready"
      intervalSec: 5
      backoff: 1.5         # Custom backoff multiplier
      maxIntervalSec: 300  # Cap at 5 minutes
      limit: 60

Executor Configuration

Field	Type	Description	Default
executor	object	Executor configuration	Shell executor

steps:
  - executor:
      type: docker
      config:
        image: python:3.11
        volumes:
          - /data:/data:ro
        env:
          - API_KEY=${API_KEY}
    command: python process.py

Distributed Execution

Field	Type	Description	Default
workerSelector	object	Worker label requirements for distributed execution	-

When using distributed execution, specify workerSelector to route tasks to workers with matching labels:

steps:
  - run: gpu-training
---
# Run on a worker with gpu
name: gpu-training
workerSelector:
  gpu: "true"
  memory: "64G"
steps:
  - python train_model.py

Worker Selection Rules:

• All labels in workerSelector must match exactly on the worker
• Label values are case-sensitive strings
• Steps without workerSelector can run on any available worker
• If no workers match the selector, the task waits until a matching worker is available

See Distributed Execution for complete documentation.

Variable Substitution

Parameter References

params:
  - USER: john
  - DOMAIN: example.com

steps:
  - echo "Hello ${USER} from ${DOMAIN}"

Environment Variables

env:
  - API_URL: https://api.example.com
  - API_KEY: ${SECRET_API_KEY}  # From system env

steps:
  - curl -H "X-API-Key: ${API_KEY}" ${API_URL}

Loading Environment from .env Files

The dotenv field allows loading environment variables from .env files:

# Default behavior - loads .env file if it exists
# No dotenv field needed, defaults to [".env"]

# Load specific .env file
dotenv: .env.production

# Load multiple .env files (later files override earlier ones)
dotenv:
  - .env.defaults
  - .env.local

# Disable .env loading
dotenv: []

Important Notes:

• If dotenv is not specified, Dagu automatically tries to load .env file
• Files are loaded relative to the DAG's workingDir
• Later files in the array override variables from earlier files
• System environment variables take precedence over .env file variables
• .env files are loaded at DAG startup, before any steps execute

Example .env file:

# .env file
DATABASE_URL=postgres://localhost/mydb
API_KEY=secret123
DEBUG=true

# DAG using .env variables
workingDir: /app
dotenv: .env          # Optional, this is the default

steps:
  - psql ${DATABASE_URL}
  - echo "Debug is ${DEBUG}"

Command Substitution

steps:
  - echo "Today is `date +%Y-%m-%d`"
    
  - command: deploy.sh
    preconditions:
      - condition: "`git branch --show-current`"
        expected: "main"

Output Variables

steps:
  - command: cat VERSION
    output: VERSION
  - command: docker build -t app:${VERSION} .

JSON Path Access

steps:
  - command: cat config.json
    output: CONFIG
  - command: echo "Port is ${CONFIG.server.port}"

Special Variables

These variables are automatically available:

Variable	Description
DAG_NAME	Current DAG name
DAG_RUN_ID	Unique run identifier
DAG_RUN_LOG_FILE	Path to workflow log
DAG_RUN_STEP_NAME	Current step name
DAG_RUN_STEP_STDOUT_FILE	Step stdout file path
DAG_RUN_STEP_STDERR_FILE	Step stderr file path
ITEM	Current item in parallel execution

Complete Example

name: production-etl
description: Daily ETL pipeline for production data
tags: [production, etl, critical]
schedule: "0 2 * * *"

maxActiveRuns: 1
maxActiveSteps: 5
timeoutSec: 7200
histRetentionDays: 90

params:
  - DATE: "`date +%Y-%m-%d`"
  - ENVIRONMENT: production

env:
  - DATA_DIR: /data/etl
  - LOG_LEVEL: info
  
dotenv:
  - /etc/dagu/production.env

# Default container for all steps
container:
  image: python:3.11-slim
  pullPolicy: missing
  env:
    - PYTHONUNBUFFERED=1
  volumes:
    - ./data:/data
    - ./scripts:/scripts:ro

preconditions:
  - condition: "`date +%u`"
    expected: "re:[1-5]"  # Weekdays only

steps:
  - ./scripts/validate.sh
    
  - command: python extract.py --date=${DATE}
    depends: validate-environment
    output: RAW_DATA_PATH
    retryPolicy:
      limit: 3
      intervalSec: 300
    
  - run: transform-module
    parallel:
      items: [customers, orders, products]
      maxConcurrent: 2
    params: "TYPE=${ITEM} INPUT=${RAW_DATA_PATH}"
    continueOn:
      failure: false

 # Use different executor for this step   
  - executor:
      type: docker
      config:
        image: postgres:16
        env:
          - PGPASSWORD=${DB_PASSWORD}
    command: psql -h ${DB_HOST} -U ${DB_USER} -f load.sql
    
  - command: python validate_results.py --date=${DATE}
    depends: load-data
    mailOnError: true

handlerOn:
  success:
    command: |
      echo "ETL completed successfully for ${DATE}"
      ./scripts/notify-success.sh
  failure:
    executor:
      type: mail
      config:
        to: [email protected]
        subject: "ETL Failed - ${DATE}"
        body: "Check logs at ${DAG_RUN_LOG_FILE}"
        attachLogs: true
  exit:
    command: ./scripts/cleanup.sh ${DATE}

mailOn:
  failure: true
  
smtp:
  host: smtp.company.com
  port: "587"
  username: [email protected]