feat(devops): diagnose slow HK requests and dependency timings

src/lib/performance-diagnostics.test.ts

@@ -0,0 +1,87 @@
+import { describe, expect, it } from "vitest";
+import {
+	collectPerformance,
+	instrumentDatabase,
+	measureDependency,
+	routeTemplate,
+} from "./performance-diagnostics";
+
+describe("performance diagnostics", () => {
+	it("isolates concurrent requests and preserves results and errors", async () => {
+		const error = new Error("private SQL parameters");
+		const [a, b] = await Promise.all([
+			collectPerformance(async () => {
+				await measureDependency("database", async () => 42);
+				await expect(
+					measureDependency("external", async () => {
+						throw error;
+					}),
+				).rejects.toBe(error);
+				return "first";
+			}),
+			collectPerformance(async () => "second"),
+		]);
+		expect(a.value).toBe("first");
+		expect(a.metrics.database.count).toBe(1);
+		expect(a.metrics.external.count).toBe(1);
+		expect(a.metrics.external.errors).toBe(1);
+		expect(b.metrics.database.count).toBe(0);
+		expect(JSON.stringify(a.metrics)).not.toContain("private");
+	});
+	it("measures pool and transaction queries without changing receiver or arguments", async () => {
+		const connection = {
+			query: async (sql: string) => sql,
+			release() {
+				return this;
+			},
+		};
+		const original = {
+			marker: 42,
+			async execute(value: number) {
+				return this.marker + value;
+			},
+			async getConnection() {
+				return connection;
+			},
+		};
+		const pool = instrumentDatabase(original);
+		const result = await collectPerformance(async () => {
+			expect(await pool.execute(8)).toBe(50);
+			const conn = await pool.getConnection();
+			expect(await conn.query("secret SQL")).toBe("secret SQL");
+			expect(conn.release()).toBe(connection);
+		});
+		expect(result.metrics.database.count).toBe(2);
+		expect(JSON.stringify(result.metrics)).not.toContain("secret");
+	});
+	it("removes query strings and dynamic path values including encoded catch-all segments", () => {
+		expect(
+			routeTemplate("/api/admin/users/Life?token=private", {
+				username: "Life",
+			}),
+		).toBe("/api/admin/users/[username]");
+		expect(
+			routeTemplate("/api/admin/assets/a%20b/file.png", {
+				path: ["a b", "file.png"],
+			}),
+		).toBe("/api/admin/assets/[path]/[path]");
+	});
+});
+
+it("does not change a completed snapshot when background work finishes", async () => {
+	let finish!: () => void;
+	let background!: Promise<void>;
+	const result = await collectPerformance(async () => {
+		background = measureDependency(
+			"external",
+			() =>
+				new Promise<void>((resolve) => {
+					finish = resolve;
+				}),
+		);
+	});
+	expect(result.metrics.external.count).toBe(0);
+	finish();
+	await background;
+	expect(result.metrics.external.count).toBe(0);
+});