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Resume When Network Returns ​

Problem ​

Jobs enqueued while offline remain queued until the processor next claims them. The application should flush the outbox as soon as connectivity returns rather than waiting for the next scheduled wake.

Solution ​

Subscribe to Sentinel's network state and call flush() when online becomes true. Postmaster does not import Sentinel; the integration lives in application code.

ts
import { createNetwork } from '@vielzeug/sentinel';
import { createPostmaster, defineJobs } from '@vielzeug/postmaster';
import { createIndexedDbPostmasterStore } from '@vielzeug/postmaster/indexeddb';

const store = createIndexedDbPostmasterStore({ name: 'outbox' });
const postmaster = createPostmaster({
  jobs: defineJobs({
    sync: {
      version: 1,
      validate: (v: unknown) => v as { id: string },
      key: (p) => p.id,
      execute: async (payload, { key, signal }) => {
        await fetch(`/api/sync/${payload.id}`, {
          headers: { 'Idempotency-Key': key },
          signal,
        });
      },
      retry: { maxAttempts: 20, shouldRetry: (error) => error instanceof TypeError },
    },
  }),
  store,
});

const network = createNetwork();
const unsubscribe = network.subscribe(() => {
  if (network.value.online) void postmaster.flush();
});

await postmaster.start();

// On teardown:
// unsubscribe();
// network.dispose();
// await postmaster.dispose();
// await store.dispose();

Pitfalls ​

  • navigator.onLine is a hint, not proof that a request will succeed; keep shouldRetry defensive.
  • flush() processes every available job synchronously; avoid calling it on every network event if the outbox is large.
  • Dispose the Sentinel subscription before the Postmaster to avoid flushing after teardown.