perf(web): queue dashboard tile hydration

apps/web/src/lib/client/dashboard-refresh.test.ts

@@ -1,7 +1,9 @@
 import { describe, expect, test } from "vitest";
 import {
   attachDashboardRefreshLifecycle,
+  createDashboardTileBackoff,
   createDashboardRequestAborter,
+  runDashboardHydrationQueue,
   shouldPauseDashboardRefresh,
 } from "./dashboard-refresh";
 
@@ -73,4 +75,69 @@ describe("dashboard refresh lifecycle", () => {
 
     expect(calls).toEqual(["pause", "pause", "pause", "load", "load"]);
   });
+
+  test("limits tile hydration concurrency", async () => {
+    let active = 0;
+    let maxActive = 0;
+    const started: number[] = [];
+    const releases = new Map<number, () => void>();
+
+    const queue = runDashboardHydrationQueue({
+      concurrency: 2,
+      items: [1, 2, 3, 4],
+      signal: new AbortController().signal,
+      hydrate: async (item) => {
+        active += 1;
+        maxActive = Math.max(maxActive, active);
+        started.push(item);
+        await new Promise<void>((resolve) => releases.set(item, resolve));
+        active -= 1;
+      },
+    });
+
+    await waitFor(() => started.length === 2);
+    expect(started).toEqual([1, 2]);
+    expect(maxActive).toBe(2);
+
+    releases.get(1)?.();
+    await waitFor(() => started.length === 3);
+    expect(started).toEqual([1, 2, 3]);
+    expect(maxActive).toBe(2);
+
+    releases.get(2)?.();
+    releases.get(3)?.();
+    await waitFor(() => started.length === 4);
+    releases.get(4)?.();
+    await queue;
+    expect(maxActive).toBe(2);
+  });
+
+  test("backs off failed tile keys and resets after success", () => {
+    const backoff = createDashboardTileBackoff();
+
+    backoff.recordFailure("telemetry:infra-ram", 1_000);
+    expect(backoff.canAttempt("telemetry:infra-ram", 15_999)).toBe(false);
+    expect(backoff.canAttempt("telemetry:infra-ram", 16_000)).toBe(true);
+
+    backoff.recordFailure("telemetry:infra-ram", 16_000);
+    expect(backoff.canAttempt("telemetry:infra-ram", 45_999)).toBe(false);
+    expect(backoff.canAttempt("telemetry:infra-ram", 46_000)).toBe(true);
+
+    backoff.recordFailure("telemetry:infra-ram", 46_000);
+    backoff.recordFailure("telemetry:infra-ram", 106_000);
+    expect(backoff.canAttempt("telemetry:infra-ram", 225_999)).toBe(false);
+    expect(backoff.canAttempt("telemetry:infra-ram", 226_000)).toBe(true);
+
+    backoff.recordSuccess("telemetry:infra-ram");
+    expect(backoff.canAttempt("telemetry:infra-ram", 107_000)).toBe(true);
+  });
 });
+
+async function waitFor(predicate: () => boolean) {
+  for (let attempt = 0; attempt < 20; attempt += 1) {
+    if (predicate()) return;
+    await Promise.resolve();
+  }
+
+  throw new Error("condition was not met");
+}