dagu/docs/reference/continue-on.md

Continue On Conditions

The continueOn configuration allows workflows to continue execution even when steps encounter failures, specific exit codes, or produce certain outputs. This powerful feature enables resilient workflows that can handle errors gracefully and implement sophisticated control flow patterns.

Overview

By default, Dagu stops workflow execution when a step fails (returns a non-zero exit code). The continueOn configuration overrides this behavior, allowing you to:

• Continue execution after failures
• Handle specific exit codes differently
• React to command output patterns
• Mark steps as successful despite failures
• Build fault-tolerant workflows

Configuration Fields

The continueOn configuration supports the following fields:

Field	Type	Description	Default
failure	boolean	Continue execution when the step fails	false
skipped	boolean	Continue execution when the step is skipped	false
exitCode	array	Continue execution for specific exit codes	[]
output	array	Continue execution when output matches patterns	[]
markSuccess	boolean	Mark the step as successful when conditions are met	false

Field Details

failure

When set to true, the workflow continues even if the step fails with any non-zero exit code.

steps:
  - name: optional-cleanup
    command: rm -rf /tmp/cache/*
    continueOn:
      failure: true

skipped

When set to true, the workflow continues when a step is skipped due to unmet preconditions.

steps:
  - name: conditional-task
    command: echo "Processing"
    preconditions:
      - condition: "${ENABLE_FEATURE}"
        expected: "true"
    continueOn:
      skipped: true

exitCode

An array of specific exit codes that should not stop the workflow. This is useful when dealing with commands that use non-zero exit codes for non-error conditions.

steps:
  - name: check-service
    command: echo "Health check OK"
    continueOn:
      exitCode: [0, 1, 2]  # 0=healthy, 1=warning, 2=maintenance

output

An array of patterns to match against the command's stdout output. Supports both literal strings and regular expressions (prefixed with re:).

steps:
  - name: validate-data
    command: echo "Validating"
    continueOn:
      output:
        - "WARNING"                    # Literal string match (substring)
        - "SKIP"                      # Another literal string
        - "re:^INFO:.*"               # Regex: lines starting with "INFO:"
        - "re:WARN-[0-9]+"            # Regex: WARN- followed by numbers

Pattern Matching Rules:

• Literal patterns: Matched as substrings (e.g., "WARNING" matches "WARNING: Low memory")
• Regex patterns: Must start with re: prefix (e.g., re:^ERROR.*)
• Patterns are matched against each line of stdout only (stderr is not checked)
• Matching is case-sensitive

markSuccess

When set to true, the step is marked as successful if any of the continue conditions are met, even if it would normally be considered a failure.

steps:
  - name: best-effort-optimization
    command: echo "Optimizing"
    continueOn:
      failure: true
      markSuccess: true  # Step shows as successful in UI/logs

Common Patterns

Optional Steps

For steps that are nice-to-have but not critical:

steps:
  - name: cache-warmup
    command: echo "Warming cache"
    continueOn:
      failure: true
      
  - name: main-process
    command: echo "Processing"

Handling Known Exit Codes

When working with tools that use exit codes for non-error states:

steps:
  - name: git-diff
    command: git diff --exit-code
    continueOn:
      exitCode: [0, 1]  # 0=no changes, 1=changes exist
      
  - name: process-changes
    command: echo "Handling changes"

Warning Detection

Continue execution but handle warnings differently:

steps:
  - name: lint-code
    command: eslint .
    continueOn:
      output: ["WARNING", "re:.*warning.*"]
      exitCode: [0, 1]  # 0=no issues, 1=warnings only
      
  - name: strict-lint
    command: eslint . --max-warnings 0
    continueOn:
      failure: false  # This one must pass

Graceful Degradation

Build workflows that degrade gracefully:

steps:
  - name: try-optimal-method
    command: echo "Processing with optimal settings"
    continueOn:
      failure: true
      
  - name: fallback-method
    command: echo "Processing with fallback settings"
    preconditions:
      - condition: "${TRY_OPTIMAL_METHOD_EXIT_CODE}"
        expected: "re:[1-9][0-9]*"  # Only run if previous failed

Complex Output Matching

React to specific output patterns:

steps:
  - name: deployment-check
    command: kubectl rollout status deployment/app
    continueOn:
      output:
        - "re:Waiting for.*replicas"
        - "re:deployment.*not found"
        - "Unable to connect"
      exitCode: [1]
      
  - name: handle-deployment-issue
    command: echo "Fixing deployment"

Interaction with Other Features

With Retry Policies

continueOn is evaluated after all retries are exhausted:

steps:
  - name: flaky-service
    command: echo "Calling service"
    retryPolicy:
      limit: 3
      intervalSec: 5
    continueOn:
      exitCode: [503]  # Continue if still 503 after retries

With Lifecycle Handlers

Steps that continue on failure still trigger onFailure handlers:

handlerOn:
  failure:
    command: echo "Logging failure"

steps:
  - name: optional-step
    command: echo "Running optional task"
    continueOn:
      failure: true  # Continues, but failure handler still runs

With Dependencies

Dependent steps see the actual status unless markSuccess is used:

steps:
  - name: step-a
    command: exit 1
    continueOn:
      failure: true
      markSuccess: false  # Default
      
  - name: step-b
    command: echo "Step A status: failed"
    depends: [step-a]  # Runs because of continueOn
    
  - name: step-c
    command: exit 1
    continueOn:
      failure: true
      markSuccess: true  # Override status
      
  - name: step-d
    command: echo "Step C status: success"
    depends: [step-c]  # Sees step-c as successful

Examples

Database Migration with Warnings

steps:
  - name: run-migration
    command: echo "Running migration"
    continueOn:
      output:
        - "re:WARNING:.*already exists"
        - "re:NOTICE:.*will be created"
      exitCode: [0, 1]  # 1 might indicate warnings
      
  - name: verify-migration
    command: echo "Verifying database"

Multi-Cloud Deployment

steps:
  - name: deploy-aws
    command: echo "Deploying to AWS"
    continueOn:
      failure: true  # Continue even if AWS fails
      
  - name: deploy-gcp
    command: echo "Deploying to GCP"
    continueOn:
      failure: true  # Continue even if GCP fails
      
  - name: verify-deployment
    command: echo "Verifying cloud deployment"
    continueOn:
      failure: false  # At least one cloud must be working

Service Health Check

steps:
  - name: check-primary
    command: curl -f https://primary.example.com/health
    continueOn:
      exitCode: [0, 22, 7]  # 22=HTTP error, 7=connection failed
      
  - name: check-secondary
    command: curl -f https://secondary.example.com/health
    preconditions:
      - condition: "${CHECK_PRIMARY_EXIT_CODE}"
        expected: "re:[1-9][0-9]*"  # Only if primary failed