Server-Timing

src/common/interceptors/server-timing.interceptor.ts

@@ -0,0 +1,42 @@
+import {
+  CallHandler,
+  ExecutionContext,
+  Injectable,
+  Logger,
+  NestInterceptor,
+} from '@nestjs/common';
+import { Observable } from 'rxjs';
+import { finalize } from 'rxjs/operators';
+
+@Injectable()
+export class ServerTimingInterceptor implements NestInterceptor {
+  private readonly logger = new Logger(ServerTimingInterceptor.name);
+
+  intercept(context: ExecutionContext, next: CallHandler): Observable<unknown> {
+    const http = context.switchToHttp();
+    const response = http.getResponse<{
+      setHeader(name: string, value: string): void;
+      getHeader(name: string): string | number | string[] | undefined;
+    }>();
+    const request = http.getRequest<{ method?: string; url?: string }>();
+    const start = performance.now();
+
+    return next.handle().pipe(
+      finalize(() => {
+        const dur = Math.max(0, Math.round(performance.now() - start));
+        const existing = response.getHeader('Server-Timing');
+        const total = `total;dur=${dur}`;
+        response.setHeader(
+          'Server-Timing',
+          existing ? `${String(existing)}, ${total}` : total,
+        );
+        if (process.env.LOG_SERVER_TIMING === 'true') {
+          const route = request.url ?? '';
+          this.logger.log(
+            `${request.method ?? '?'} ${route} total;dur=${dur}`,
+          );
+        }
+      }),
+    );
+  }
+}