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Typed Error Handling ​

Problem ​

Retry, load shedding, and shutdown require different worker failure handling.

Solution ​

Branch on Familiar's typed errors.

ts
import {
  FamiliarQueueFullError,
  FamiliarTaskError,
  FamiliarTimeoutError,
} from '@vielzeug/familiar';

function handleWorkerError(error: unknown): void {
  if (error instanceof FamiliarTimeoutError) console.log('retry later');
  else if (error instanceof FamiliarQueueFullError) console.log('shed load');
  else if (error instanceof FamiliarTaskError) throw error.cause;
  else throw error;
}

try {
  throw new FamiliarTimeoutError(500);
} catch (error) {
  handleWorkerError(error);
}

Pitfalls ​

  • AbortError represents caller cancellation, not Familiar failure.
  • FamiliarTaskError.cause carries worker handler failure.