Implement push

backend/client-state.ts

@@ -15,20 +15,12 @@ export interface Socket {
 export type ClientState = {
   socket: Socket;
 
-  // A list of mutations awaiting application from this client. This list has
-  // a funny invariant. It is sorted by mutationID AND serverTimestamp ascending.
-  // The list needs to be sorted by mutationID because we need to process
-  // mutations in that order to preserve causality. But it also needs to be sorted
-  // by serverTimestamp so that mutations get processed in an order roughly
-  // corresponding to realtime. The push handler (below) ensures this invariant
-  // is preserved by adjusting serverTimestamp if necessary so that it is
-  // monotonically increasing.
-  pending: PendingMutation[];
+  // A list of mutations awaiting application from this client. Sorted by
+  // lastMutationID and de-duplicated. The timestamps in these mutations
+  // are in the server's timeframe. Note that they will generally increase
+  // with respect to mutationID but that is not guaranteed.
+  pending: Mutation[];
 
   // How long is the client's timestamp behind the local timestamp?
   clockBehindByMs: number;
 };
-
-export type PendingMutation = Mutation & {
-  serverTimestamp: number;
-};

backend/lock.test.ts

@@ -2,6 +2,7 @@ import { expect } from "chai";
 import { test } from "mocha";
 import { resolver } from "../frontend/resolver";
 import { Lock } from "./lock";
+import { sleep } from "./test-utils";
 
 test("Lock", async () => {
   type Task = () => Promise<void>;
@@ -17,10 +18,6 @@ test("Lock", async () => {
     return [task, resolve] as [Task, () => void];
   }
 
-  function sleep(ms: number) {
-    return new Promise((resolve) => setTimeout(resolve, ms));
-  }
-
   const [t1, r1] = makeTask("t1");
   const [t2, r2] = makeTask("t2");
   const [t3, r3] = makeTask("t3");
@@ -29,18 +26,18 @@ test("Lock", async () => {
   loop.withLock(t1);
   loop.withLock(t2);
 
-  await sleep(0);
+  await sleep();
   expect(log).deep.equal(["t1 enter"]);
   r1();
-  await sleep(0);
+  await sleep();
   expect(log).deep.equal(["t1 enter", "t1 exit", "t2 enter"]);
   r2();
-  await sleep(0);
+  await sleep();
   expect(log).deep.equal(["t1 enter", "t1 exit", "t2 enter", "t2 exit"]);
 
   r3();
   loop.withLock(t3);
-  await sleep(0);
+  await sleep();
   expect(log).deep.equal([
     "t1 enter",
     "t1 exit",