Error Handling, Retry & Timeout

When a transition throws an error, the framework rolls back all changes and gives you three ways to recover: auto-retry with backoff, transition to a custom error state, or manual retry via the UI.

Retry Modes

Auto-Retry

Automatically re-run a failed transition with exponential backoff:

@Transition({ from: 'fetching', to: 'done', retry: 3 })
async fetchData() {
  await this.httpClient.call({ url: 'https://api.example.com/data' });
}

If fetchData throws, the framework retries up to 3 times with exponential delays (1s, 2s, 4s). The workflow stays at the fetching place during retries.

Custom Error Place

Route to a dedicated error state when a transition fails:

@Transition({ from: 'processing', to: 'done', retry: { place: 'error_processing' } })
async processData() {
  await this.processor.call({ data: this.rawData });
}
 
@Transition({ from: 'error_processing', to: 'done', wait: true })
async handleProcessingError() {
  // Recovery logic — user clicks a "Recover" button to trigger this
  await this.repository.save(MessageDocument, {
    role: 'assistant',
    content: 'Processing failed. Retrying with fallback strategy.',
  });
}

The workflow transitions to error_processing where you define recovery logic via wait: true transitions (buttons in the UI).

Manual Retry (Default)

When no retry config is specified, the workflow stays at the current place and shows a “Retry” button:

@Transition({ from: 'sending', to: 'sent' })
async sendEmail() {
  await this.email.call({ to: 'user@example.com', body: this.content });
}

If it fails, the user sees the error message and can retry manually. No auto-retry, no error place — just pause and let the user decide.

Hybrid: Auto-Retry + Error Place

Combine auto-retry with a fallback error state:

@Transition({
  from: 'deploying',
  to: 'deployed',
  retry: { attempts: 2, place: 'deploy_failed' },
})
async deploy() {
  await this.deployer.call({ target: 'production' });
}
 
@Transition({ from: 'deploy_failed', to: 'deployed', wait: true })
async retryDeploy() {
  // Manual recovery after auto-retries exhausted
}

Retries twice automatically. If both fail, transitions to deploy_failed for manual intervention.

Retry Configuration

retry: number                    // Shorthand: number of auto-retry attempts
retry: {
  attempts?: number,             // Auto-retry count (-1 = manual only, 0 = go to error place immediately)
  delay?: number,                // Base delay in ms (default: 1000)
  backoff?: 'fixed' | 'exponential',  // Backoff strategy (default: 'exponential')
  maxDelay?: number,             // Backoff cap in ms (default: 30000)
  place?: string,                // Custom error place when retries exhausted
}

Backoff calculation (exponential): delay * 2^(attempt - 1), capped at maxDelay.

Timeout

Kill a transition that takes too long:

@Transition({ from: 'analyzing', to: 'analyzed', timeout: 5000 })
async analyzeData() {
  await this.analyzer.call({ dataset: this.data });
}

If analyzeData takes longer than 5 seconds, it’s interrupted with Error: Transition 'analyzeData' timed out after 5000ms. The error flows through the normal retry logic — so you can combine timeout with retry:

@Transition({
  from: 'analyzing',
  to: 'analyzed',
  timeout: 5000,
  retry: 2,
})
async analyzeData() {
  await this.analyzer.call({ dataset: this.data });
}

Times out after 5s, retries up to 2 times, then falls to manual retry.

What Gets Rolled Back

When a transition fails, the framework rolls back:

• Documents created during the transition (restored from snapshot)
• Database changes within the transition’s transaction
• Workflow state stays at the pre-transition place

What is not rolled back:

• An ErrorDocument is saved after rollback as an audit trail
• The error message is stored in workflow metadata
• Workflow instance variables (this.someField) persist across retries — useful for attempt counters

ErrorDocument

Every failed transition creates an ErrorDocument with the error message:

// Automatically created by the framework:
{
  className: 'ErrorDocument',
  content: { error: 'Connection refused: api.example.com' }
}

Multiple ErrorDocuments accumulate if retries fail repeatedly — giving a full audit trail of each attempt.

Registry References

• error-retry-example-workflow  — Demonstrates all five retry modes: auto-retry, manual retry, custom error place, timeout, and hybrid