Exponential backoff retry helper for DurableObjectStub

retry.ts

import { DurableObject } from 'cloudflare:workers';

const attempts = 3;
const baseBackoff = 100;
const maxBackoff = 20000;

function getBackoff(attempt: number) {
  const backoff = baseBackoff * Math.pow(2, attempt) * Math.random();
  return Math.round(Math.min(maxBackoff, backoff));
}

type DurableObjectCallback<T extends DurableObject, R> = (
  stub: DurableObjectStub<T>,
) => Promise<R>;

export async function retry<T extends DurableObject, R>(
  namespace: DurableObjectNamespace<T>,
  name: string,
  callback: DurableObjectCallback<T, R>,
): Promise<R> {
  const id = namespace.idFromName(name);
  let attempt = 0;
  while (true) {
    try {
      const obj = namespace.get(id);
      return await callback(obj);
    } catch (error: any) {
      // Failure was not a transient internal error, so don't retry.
      if (!error.retryable) throw error;
      // Reached max attempts, don't retry.
      if (++attempt >= attempts) throw error;
      const backoff = getBackoff(attempt);
      console.log(`Caught "${error.message}" (attempt ${attempt}/${attempts})`);
      await scheduler.wait(backoff);
    }
  }
}