refactor(common,express): rename graceful shutdown option

Rename gracefulShutdown to return503OnClosing to align the HTTP
option name with Fastify's terminology. The previous name was too
vague and could imply broader behavior (connection draining, grace
periods) beyond what it actually does.

Author: manureja64

integration/graceful-shutdown/e2e/express.spec.ts

@@ -14,9 +14,9 @@ describe('Graceful Shutdown (Express)', () => {
     }
   });
 
-  it('should allow in-flight requests to complete when gracefulShutdown is enabled', async () => {
+  it('should allow in-flight requests to complete when return503OnClosing is enabled', async () => {
     app = await NestFactory.create(AppModule, new ExpressAdapter() as any, {
-      gracefulShutdown: true,
+      return503OnClosing: true,
       logger: false,
     });
     await app.listen(0);
@@ -53,7 +53,7 @@ describe('Graceful Shutdown (Express)', () => {
 
   it('should return 503 for NEW queued requests on existing connections during shutdown', async () => {
     app = await NestFactory.create(AppModule, new ExpressAdapter() as any, {
-      gracefulShutdown: true,
+      return503OnClosing: true,
       logger: false,
     });
     await app.listen(0);

packages/common/interfaces/nest-application-options.interface.ts

@@ -31,10 +31,9 @@ export interface NestApplicationOptions extends NestApplicationContextOptions {
    */
   forceCloseConnections?: boolean;
   /**
-   * Whether to enable graceful shutdown behavior.
-   * When enabled, the server will return 503 Service Unavailable for new requests
-   * during the shutdown process, but allow existing in-flight requests to complete.
+   * Whether to return 503 Service Unavailable for new requests during the shutdown process,
+   * while allowing existing in-flight requests to complete.
    * @default false
    */
-  gracefulShutdown?: boolean;
+  return503OnClosing?: boolean;
 }

packages/platform-express/adapters/express-adapter.ts

@@ -304,7 +304,7 @@ export class ExpressAdapter extends AbstractHttpAdapter<
       this.httpServer = http.createServer(this.getInstance());
     }
 
-    if (options?.gracefulShutdown) {
+    if (options?.return503OnClosing) {
       this.instance.use((req: any, res: any, next: any) => {
         if (this.isShuttingDown) {
           res.set('Connection', 'close');