backend: Add support for lifecycle events

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

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

@@ -24,6 +24,11 @@ export interface BackendFeature {
   register(reg: BackendRegistrationPoints): void;
 }
 
+// @public (undocumented)
+export interface BackendLifecycle {
+  addShutdownHook(options: ShutdownHookOptions): void;
+}
+
 // @public (undocumented)
 export interface BackendModuleConfig<TOptions> {
   // (undocumented)
@@ -158,6 +163,9 @@ export interface HttpRouterService {
 // @public (undocumented)
 export const httpRouterServiceRef: ServiceRef<HttpRouterService, 'plugin'>;
 
+// @public (undocumented)
+export const lifecycleServiceRef: ServiceRef<BackendLifecycle, 'plugin'>;
+
 // @public (undocumented)
 export interface Logger {
   // (undocumented)
@@ -235,6 +243,11 @@ export type ServiceRef<
   $$ref: 'service';
 };
 
+// @public (undocumented)
+export type ShutdownHookOptions = {
+  fn: () => Promise<void>;
+};
+
 // @public (undocumented)
 export const tokenManagerServiceRef: ServiceRef<TokenManager, 'plugin'>;
 

packages/backend-plugin-api/src/services/definitions/index.ts

@@ -28,4 +28,9 @@ export { permissionsServiceRef } from './permissionsServiceRef';
 export { schedulerServiceRef } from './schedulerServiceRef';
 export { rootLoggerServiceRef } from './rootLoggerServiceRef';
 export { pluginMetadataServiceRef } from './pluginMetadataServiceRef';
+export { lifecycleServiceRef } from './lifecycleServiceRef';
+export type {
+  BackendLifecycle,
+  ShutdownHookOptions,
+} from './lifecycleServiceRef';
 export type { PluginMetadata } from './pluginMetadataServiceRef';

packages/backend-plugin-api/src/services/definitions/lifecycleServiceRef.ts

@@ -0,0 +1,42 @@
+/*
+ * 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 { createServiceRef } from '../system/types';
+
+/**
+ * @public
+ **/
+export type ShutdownHookOptions = {
+  fn: () => Promise<void>;
+};
+
+/**
+ * @public
+ **/
+export interface BackendLifecycle {
+  /**
+   * Register a function to be called and when the backend is shutting down.
+   */
+  addShutdownHook(options: ShutdownHookOptions): void;
+}
+
+/**
+ * @public
+ */
+export const lifecycleServiceRef = createServiceRef<BackendLifecycle>({
+  id: 'core.lifecycle',
+  scope: 'plugin',
+});