@asterql/sync-server

The server side of the AsterQL sync protocol: per-scope envelope ledgers, sequenced publishing, replay from client cursors, and a transport-agnostic connection handler. Pairs with @asterql/sync on the client.

Install

npm install @asterql/sync-server @asterql/view-protocol

Usage

import { SyncHub, InMemorySyncLedger } from "@asterql/sync-server";
import { WebSocketServer } from "ws";

const hub = new SyncHub({
  ledger: new InMemorySyncLedger({ retain: 10_000 }),
  authorize: (scope, user) => canRead(user, scope),
});

const wss = new WebSocketServer({ noServer: true });
server.on("upgrade", (request, socket, head) => {
  const user = authenticate(request); // your session check
  if (!user) return socket.destroy();
  wss.handleUpgrade(request, socket, head, (ws) => {
    const connection = hub.connect(ws, user);
    ws.on("message", (data) => connection.handleMessage(String(data)));
    ws.on("close", () => connection.close());
  });
});

// The one write path — mutations publish envelopes; the ledger assigns seq:
await hub.publish("run:r1", (seq) => ({
  eventId: crypto.randomUUID(),
  kind: "patch",
  scope: "run:r1",
  seq,
  entities: [
    {
      key: "message:m1",
      patches: [{ op: "appendText", path: "/text", delta: "…" }],
    },
  ],
}));

Semantics

• Ledgers assign sequence numbers. publish(scope, makeEnvelope) appends atomically; the ledger passes the next contiguous seq to your factory. Clients replay any range gap-free because the ledger — not delivery order — is the source of truth.
• Replay from cursors. A sub with since replays everything after the cursor before going live; since omitted means live-from-now. A cursor below the retention floor gets scopeError snapshot_required — the client re-bootstraps from a registered view and resubscribes.
• Seed snapshots. Publish a kind: "snapshot" envelope as each scope's first entry so replay-from-zero is deterministic for any consumer.
• Transport-agnostic. connect() takes anything with send(string); feed inbound frames to handleMessage. Works with ws, Durable Object sockets, or test fakes.
• Multi-instance. Pass a shared SyncBus (Postgres LISTEN/NOTIFY, Redis pub/sub) and a shared persistent SyncScopeLedger; the in-memory implementations are correct for one process and for tests.