backend-app-api: move signal handlers to backend initializer + exit

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/red-kiwis-compare.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-app-api': patch
+---
+
+The shutdown signal handlers are now installed as part of the backend instance rather than the lifecycle service, and explicitly cause the process to exit.

packages/backend-app-api/src/services/implementations/rootLifecycle/rootLifecycleFactory.ts

@@ -22,11 +22,8 @@ import {
   LoggerService,
 } from '@backstage/backend-plugin-api';
 
-const CALLBACKS = ['SIGTERM', 'SIGINT', 'beforeExit'];
 export class BackendLifecycleImpl implements RootLifecycleService {
-  constructor(private readonly logger: LoggerService) {
-    CALLBACKS.map(signal => process.on(signal, () => this.shutdown()));
-  }
+  constructor(private readonly logger: LoggerService) {}
 
   #isCalled = false;
   #shutdownTasks: Array<LifecycleServiceShutdownHook> = [];

packages/backend-app-api/src/wiring/BackendInitializer.ts

@@ -87,6 +87,18 @@ export class BackendInitializer {
     }
     this.#started = true;
 
+    for (const event of ['SIGTERM', 'SIGINT', 'beforeExit']) {
+      process.on(event, async () => {
+        try {
+          await this.stop();
+          process.exit(0);
+        } catch (error) {
+          console.error(error);
+          process.exit(1);
+        }
+      });
+    }
+
     // Initialize all root scoped services
     for (const ref of this.#serviceHolder.getServiceRefs()) {
       if (ref.scope === 'root') {