document, add tests

Signed-off-by: Johan Haals <johan.haals@gmail.com>

packages/backend-app-api/api-report.md

@@ -67,7 +67,7 @@ export type HttpRouterFactoryOptions = {
   indexPlugin?: string;
 };
 
-// @public (undocumented)
+// @public
 export const lifecycleFactory: (
   options?: undefined,
 ) => ServiceFactory<BackendLifecycle>;

packages/backend-app-api/src/services/implementations/lifecycleService.test.ts

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { getVoidLogger } from '@backstage/backend-common';
+import { BackendLifecycleImpl } from './lifecycleService';
+
+describe('lifecycleService', () => {
+  it('should execute registered shutdown hook', async () => {
+    const service = new BackendLifecycleImpl(getVoidLogger());
+    const hook = jest.fn();
+    service.addShutdownHook({
+      pluginId: 'test',
+      fn: async () => {
+        hook();
+      },
+    });
+    // should not execute the hook more than once.
+    await service.shutdown();
+    await service.shutdown();
+    await service.shutdown();
+    expect(hook).toHaveBeenCalledTimes(1);
+  });
+
+  it('should not throw errors', async () => {
+    const service = new BackendLifecycleImpl(getVoidLogger());
+    service.addShutdownHook({
+      pluginId: 'test',
+      fn: async () => {
+        throw new Error('oh no');
+      },
+    });
+    await expect(service.shutdown()).resolves.toBeUndefined();
+  });
+});

packages/backend-app-api/src/services/implementations/lifecycleService.ts

@@ -25,7 +25,7 @@ import {
 import { Logger } from 'winston';
 
 const CALLBACKS = ['SIGTERM', 'SIGINT', 'beforeExit'];
-class BackendLifecycleImpl {
+export class BackendLifecycleImpl {
   constructor(private readonly logger: Logger) {
     CALLBACKS.map(signal => process.on(signal, () => this.shutdown()));
   }
@@ -76,7 +76,9 @@ class PluginScopedLifecycleImpl implements BackendLifecycle {
   }
 }
 
-/** @public */
+/**
+ * Allows plugins to register shutdown hooks that are run when the process is about to exit.
+ * @public */
 export const lifecycleFactory = createServiceFactory({
   service: lifecycleServiceRef,
   deps: {