perf(web): cache dashboard tile responses

apps/web/src/server/routes/dashboard.test.ts

@@ -1,6 +1,12 @@
 import { describe, expect, test, vi } from "vitest";
 import { dimensionLabDashboardFixture } from "$lib/dashboard-seed/dimensionlab";
-import { loadDashboardResponse, loadDashboardTileResponse } from "./dashboard";
+import {
+  createDashboardTileCache,
+  dashboardTileCacheKey,
+  handleDashboardTileRoute,
+  loadDashboardResponse,
+  loadDashboardTileResponse,
+} from "./dashboard";
 
 describe("dashboard API route", () => {
   test("returns the ready dashboard shell without hydrating live datasources", async () => {
@@ -145,6 +151,243 @@ describe("dashboard API route", () => {
     });
   });
 
+  test("caches ready tile responses until the tile ttl expires", async () => {
+    const cache = createDashboardTileCache();
+    let now = 1_000;
+    const fetch = vi.fn(async () =>
+      jsonResponse({
+        status: "UP",
+        ping: 42,
+      }),
+    );
+    const tile = { kind: "service", groupId: "essentials", id: "vaultwarden" } as const;
+
+    const first = await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now,
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+    const second = await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now + 29_999,
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+    now += 30_001;
+    const third = await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now,
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+
+    expect(first).toEqual(second);
+    expect(third.state).toBe("ready");
+    expect(fetch).toHaveBeenCalledTimes(2);
+  });
+
+  test("keeps telemetry tiles cached for fifteen seconds", async () => {
+    const cache = createDashboardTileCache();
+    let now = 1_000;
+    const fetch = telemetryFetch();
+    const tile = { kind: "telemetry", id: "infra-ram" } as const;
+
+    await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now,
+      prometheusBaseUrl: "https://prometheus.example",
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+    await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now + 14_999,
+      prometheusBaseUrl: "https://prometheus.example",
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+    now += 15_001;
+    await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now,
+      prometheusBaseUrl: "https://prometheus.example",
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+
+    expect(fetch).toHaveBeenCalledTimes(4);
+  });
+
+  test("keeps weather module tiles cached for ten minutes", async () => {
+    const cache = createDashboardTileCache();
+    let now = 1_000;
+    const fetch = vi.fn(async () =>
+      jsonResponse({
+        current: {
+          apparent_temperature: 19,
+          temperature_2m: 20,
+          weather_code: 0,
+          wind_speed_10m: 11,
+        },
+      }),
+    );
+    const tile = { kind: "module", id: "weather-amsterdam" } as const;
+
+    await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now,
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+    await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now + 599_999,
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+    now += 600_001;
+    await loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => now,
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+
+    expect(fetch).toHaveBeenCalledTimes(2);
+  });
+
+  test("coalesces concurrent tile requests for the same cache key", async () => {
+    const cache = createDashboardTileCache();
+    let resolveFetch: ((response: Response) => void) | undefined;
+    const fetch = vi.fn(() =>
+      new Promise<Response>((resolve) => {
+        resolveFetch = resolve;
+      })
+    );
+    const tile = { kind: "service", groupId: "essentials", id: "vaultwarden" } as const;
+
+    const first = loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => 1_000,
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+    const second = loadDashboardTileResponse(tile, {
+      fetch,
+      now: () => 1_000,
+      refreshSeedDocument: true,
+      seedIfEmpty: true,
+      tileCache: cache,
+    });
+
+    await Promise.resolve();
+    expect(fetch).toHaveBeenCalledTimes(1);
+
+    resolveFetch?.(jsonResponse({ status: "UP", ping: 42 }));
+    expect(await first).toEqual(await second);
+  });
+
+  test("uses structured tile cache keys when identifiers contain delimiters", () => {
+    expect(
+      dashboardTileCacheKey({ kind: "service", groupId: "a:b", id: "c" }),
+    ).not.toBe(
+      dashboardTileCacheKey({ kind: "service", groupId: "a", id: "b:c" }),
+    );
+    expect(
+      dashboardTileCacheKey({ kind: "status", stripId: "a:b", id: "c" }),
+    ).not.toBe(
+      dashboardTileCacheKey({ kind: "status", stripId: "a", id: "b:c" }),
+    );
+  });
+
+  test("uses thirty-second status aggregate and five-minute static status ttl buckets", async () => {
+    const cache = createDashboardTileCache();
+    const fetch = vi.fn(async () => jsonResponse({ status: "UP", ping: 42 }));
+    const serviceCheckCount = dimensionLabDashboardFixture.serviceGroups
+      .flatMap((group) => group.services).length;
+
+    await loadDashboardTileResponse(
+      { kind: "status", stripId: "footer-status", id: "system-status" },
+      {
+        fetch,
+        now: () => 1_000,
+        refreshSeedDocument: true,
+        seedIfEmpty: true,
+        tileCache: cache,
+      },
+    );
+    await loadDashboardTileResponse(
+      { kind: "status", stripId: "footer-status", id: "system-status" },
+      {
+        fetch,
+        now: () => 31_001,
+        refreshSeedDocument: true,
+        seedIfEmpty: true,
+        tileCache: cache,
+      },
+    );
+
+    await loadDashboardTileResponse(
+      { kind: "status", stripId: "footer-status", id: "auto-refresh" },
+      {
+        fetch,
+        now: () => 1_000,
+        refreshSeedDocument: true,
+        seedIfEmpty: true,
+        tileCache: cache,
+      },
+    );
+    await loadDashboardTileResponse(
+      { kind: "status", stripId: "footer-status", id: "auto-refresh" },
+      {
+        fetch,
+        now: () => 300_999,
+        refreshSeedDocument: true,
+        seedIfEmpty: true,
+        tileCache: cache,
+      },
+    );
+    await loadDashboardTileResponse(
+      { kind: "status", stripId: "footer-status", id: "auto-refresh" },
+      {
+        fetch,
+        now: () => 301_001,
+        refreshSeedDocument: true,
+        seedIfEmpty: true,
+        tileCache: cache,
+      },
+    );
+
+    expect(fetch).toHaveBeenCalledTimes(serviceCheckCount * 2);
+  });
+
+  test("serves tile route responses with short private cache headers", async () => {
+    const response = await handleDashboardTileRoute(
+      "/api/dashboard/tile/service/essentials/vaultwarden",
+      {
+        fetch: vi.fn(async () => jsonResponse({ status: "UP", ping: 42 })),
+        refreshSeedDocument: true,
+        seedIfEmpty: true,
+        tileCache: createDashboardTileCache(),
+      },
+    );
+
+    expect(response.headers.get("cache-control")).toBe(
+      "private, max-age=5, stale-while-revalidate=30",
+    );
+  });
+
   test("does not hydrate tile routes when live datasources are disabled", async () => {
     const previous = process.env.DISABLE_LIVE_DATASOURCES;
     process.env.DISABLE_LIVE_DATASOURCES = "1";
@@ -179,3 +422,43 @@ function jsonResponse(payload: unknown): Response {
     headers: { "content-type": "application/json" },
   });
 }
+
+function telemetryFetch() {
+  return vi.fn(async (input: RequestInfo | URL) => {
+    const url = String(input);
+
+    if (url.startsWith("https://prometheus.example/api/v1/query_range")) {
+      return jsonResponse({
+        status: "success",
+        data: {
+          result: [
+            {
+              metric: { host: "linux-infra" },
+              values: [
+                [1771430000, "10"],
+                [1771430060, "20"],
+                [1771430120, "42"],
+              ],
+            },
+          ],
+        },
+      });
+    }
+
+    if (url.startsWith("https://prometheus.example/api/v1/query")) {
+      return jsonResponse({
+        status: "success",
+        data: {
+          result: [
+            {
+              metric: { host: "linux-infra" },
+              value: [1771430400, "42"],
+            },
+          ],
+        },
+      });
+    }
+
+    throw new Error(`Unhandled test request: ${url}`);
+  });
+}

apps/web/src/server/routes/dashboard.ts

@@ -1,3 +1,4 @@
+import type { DashboardDocument } from "@dimensionlab/dashboard-model";
 import {
   loadDashboardRuntime,
   type DashboardRuntimeOptions,
@@ -19,6 +20,63 @@ export interface LoadDashboardResponseOptions
     DatasourceResolutionOptions {
   disableLiveDatasources?: boolean;
   hydrateLiveDatasources?: boolean;
+  now?: () => number;
+  tileCache?: DashboardTileCache;
+}
+
+interface DashboardTileCacheEntry {
+  expiresAt: number;
+  response: DashboardTileResolution;
+}
+
+export interface DashboardTileCache {
+  resolve(
+    key: string,
+    ttlMs: number,
+    now: number,
+    load: () => Promise<DashboardTileResolution>,
+  ): Promise<DashboardTileResolution>;
+}
+
+const dashboardTileResponseHeaders = {
+  "Cache-Control": "private, max-age=5, stale-while-revalidate=30",
+};
+
+const defaultDashboardTileCache = createDashboardTileCache();
+
+export function createDashboardTileCache(): DashboardTileCache {
+  const entries = new Map<string, DashboardTileCacheEntry>();
+  const inFlight = new Map<string, Promise<DashboardTileResolution>>();
+
+  return {
+    async resolve(key, ttlMs, now, load) {
+      const cached = entries.get(key);
+      if (cached && cached.expiresAt > now) {
+        return cached.response;
+      }
+
+      const active = inFlight.get(key);
+      if (active) return active;
+
+      const request = load()
+        .then((response) => {
+          if (response.state === "ready") {
+            entries.set(key, {
+              expiresAt: now + ttlMs,
+              response,
+            });
+          }
+
+          return response;
+        })
+        .finally(() => {
+          inFlight.delete(key);
+        });
+
+      inFlight.set(key, request);
+      return request;
+    },
+  };
 }
 
 export async function loadDashboardResponse(
@@ -88,14 +146,25 @@ export async function loadDashboardTileResponse(
     };
   }
 
-  return resolveDashboardTile(dashboard.document, tile, options);
+  const cache = options.tileCache || defaultDashboardTileCache;
+  const now = options.now?.() ?? Date.now();
+
+  return cache.resolve(
+    dashboardTileCacheKey(tile),
+    dashboardTileTtlMs(dashboard.document, tile),
+    now,
+    () => resolveDashboardTile(dashboard.document, tile, options),
+  );
 }
 
 export async function handleDashboardRoute(): Promise<Response> {
   return Response.json(await loadDashboardResponse());
 }
 
-export async function handleDashboardTileRoute(pathname: string): Promise<Response> {
+export async function handleDashboardTileRoute(
+  pathname: string,
+  options: LoadDashboardResponseOptions = {},
+): Promise<Response> {
   const tile = parseDashboardTilePath(pathname);
   if (!tile) {
     return Response.json(
@@ -104,12 +173,42 @@ export async function handleDashboardTileRoute(pathname: string): Promise<Respon
     );
   }
 
-  const response = await loadDashboardTileResponse(tile);
+  const response = await loadDashboardTileResponse(tile, options);
   return Response.json(response, {
     status: response.state === "not_found" ? 404 : 200,
+    headers: dashboardTileResponseHeaders,
   });
 }
 
+export function dashboardTileCacheKey(tile: DashboardTileReference): string {
+  return JSON.stringify(tile);
+}
+
+function dashboardTileTtlMs(
+  document: DashboardDocument,
+  tile: DashboardTileReference,
+): number {
+  if (tile.kind === "telemetry") return 15_000;
+  if (tile.kind === "service") return 30_000;
+
+  if (tile.kind === "module") {
+    const module = document.modules?.find((item) => item.id === tile.id);
+    if (
+      module?.datasource?.type === "external" &&
+      module.datasource.adapter === "weather"
+    ) {
+      return 10 * 60_000;
+    }
+    return 30_000;
+  }
+
+  if (["system-status", "uptime", "load-avg"].includes(tile.id)) {
+    return 30_000;
+  }
+
+  return 5 * 60_000;
+}
+
 function parseDashboardTilePath(pathname: string): DashboardTileReference | null {
   const parts = pathname.split("/").filter(Boolean);
   const [, dashboard, tileRoot, kind, firstId, secondId] = parts;