Handle failures

What happens when something fails, and how to go another way.

When a step fails

If a step’s function throws, the SDK saves the error and throws a StepError with the same message. Leave it, and the run fails. Catch it to go another way:

import { StepError } from '@nelkap/sdk';

export async function chargeOrder(orderId: string) {
  try {
    await nelkap.step.run('charge', () => chargeCard(orderId));
  } catch (error) {
    if (!(error instanceof StepError)) {
      throw error;
    }

    await nelkap.step.run('payment failed email', () => sendPaymentFailedEmail(orderId));

    return;
  }

  await nelkap.step.run('shipping', () => shipOrder(orderId));
}

On every call after, the failed step throws the same StepError without running again. Your code takes the same path each time.

When a run fails

A run fails when your workflow throws. Its message shows under Error on the run’s page.

Nelkap can also stop a run, with a reason of its own. See Errors.

When Nelkap turns a call down

run and emit throw a NelkapError that names the reason. Inside a workflow, a step Nelkap turns down throws one too. See Errors.

Short outages

If the SDK can’t reach Nelkap, or Nelkap asks it to slow down, the run doesn’t fail. It stops where it is, and Nelkap picks it back up a few minutes later, from its last saved step.

Run it again

Once the cause is fixed, replay the run from its page.