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
name: my-workflow          # Optional: defaults to filename
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
    command: echo "Hello"
    depends: previous-step

# 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	-

Data Fields

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

Queue Configuration

Field	Type	Description	Default
queue	string	Queue name	-

Notification Fields

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

mailOn:
  success: true
  failure: true
  
errorMail:
  from: [email protected]
  to: [email protected]
  prefix: "[ALERT]"
  attachLogs: true
  
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: ./notify-failure.sh
  cancel:
    command: ./cleanup.sh
  exit:
    command: ./always-run.sh

Step Fields

Each step in the steps array can have these fields:

Basic Fields

Field	Type	Description	Default
name	string	Required - Step name	-
command	string	Command to execute	-
script	string	Inline script (alternative to command)	-
run	string	Run another DAG	-
depends	string/array	Step dependencies	-

Execution Fields

Field	Type	Description	Default
dir	string	Working directory	Current directory
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	Step-specific environment	-
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:
  - name: process-files
    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	-

steps:
  - name: conditional-step
    command: ./deploy.sh
    preconditions:
      - condition: "${ENVIRONMENT}"
        expected: "production"
      - condition: "`git branch --show-current`"
        expected: "main"
    
  - name: optional-step
    command: ./optional.sh
    continueOn:
      failure: true
      skipped: true
      exitCode: [0, 1, 2]
      output: ["WARNING", "SKIP"]
      markSuccess: true

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

steps:
  - name: retry-example
    command: curl https://api.example.com
    retryPolicy:
      limit: 3
      intervalSec: 30
      exitCodes: [1, 255]  # Retry only on specific codes
    
  - name: repeat-example
    command: check-status.sh
    repeatPolicy:
      repeat: true
      intervalSec: 60
      condition: "${STATUS}"
      expected: "ready"

Executor Configuration

Field	Type	Description	Default
executor	object	Executor configuration	Shell executor

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

Variable Substitution

Parameter References

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

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

Environment Variables

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

steps:
  - name: call-api
    command: curl -H "X-API-Key: ${API_KEY}" ${API_URL}

Command Substitution

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

Output Variables

steps:
  - name: get-version
    command: cat VERSION
    output: VERSION
    
  - name: build
    command: docker build -t app:${VERSION} .
    depends: get-version

JSON Path Access

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

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

Execution Types

Chain (Default)

Steps execute based on dependencies:

steps:
  - name: A
    command: echo "A"
  - name: B
    command: echo "B"
    depends: A
  - name: C
    command: echo "C"
    depends: B

Parallel

All steps without dependencies run in parallel:

steps:
  - name: task1
    command: ./task1.sh
  - name: task2
    command: ./task2.sh
  - name: task3
    command: ./task3.sh

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

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

steps:
  - name: validate-environment
    command: ./scripts/validate.sh
    
  - name: extract-data
    command: python extract.py --date=${DATE}
    depends: validate-environment
    output: RAW_DATA_PATH
    retryPolicy:
      limit: 3
      intervalSec: 300
    
  - name: transform-data
    run: transform-module
    parallel:
      items: [customers, orders, products]
      maxConcurrent: 2
    params: "TYPE=${ITEM} INPUT=${RAW_DATA_PATH}"
    depends: extract-data
    continueOn:
      failure: false
    
  - name: load-data
    command: python load.py --date=${DATE}
    depends: transform-data
    env:
      - LOAD_TIMEOUT: 600
    
  - name: validate-results
    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]