feat(devops): separate public page server timing diagnostics

src/lib/performance-diagnostics.ts

@@ -7,17 +7,28 @@ export type PerformanceMetrics = Record<Dependency, Measurement> & {
 };
 const context = new AsyncLocalStorage<PerformanceMetrics>();
 
-export async function collectPerformance<T>(work: () => Promise<T>) {
+export async function collectPerformance<T>(
+	work: () => Promise<T>,
+	onComplete?: (metrics: PerformanceMetrics) => void,
+) {
 	const metrics: PerformanceMetrics = {
 		durationMs: 0,
 		database: { count: 0, durationMs: 0, errors: 0 },
 		external: { count: 0, durationMs: 0, errors: 0 },
 	};
 	const start = performance.now();
-	const value = await context.run(metrics, work);
-	metrics.durationMs = performance.now() - start;
-	// Background work may keep the async context: return a detached snapshot.
-	return { value, metrics: structuredClone(metrics) };
+	try {
+		const value = await context.run(metrics, work);
+		metrics.durationMs = performance.now() - start;
+		return { value, metrics: structuredClone(metrics) };
+	} finally {
+		metrics.durationMs = performance.now() - start;
+		try {
+			onComplete?.(structuredClone(metrics));
+		} catch {
+			/* Diagnostics must not change application outcomes. */
+		}
+	}
 }
 
 export async function measureDependency<T>(