feat: update devtools almost real time using signals

Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>

plugins/devtools-backend/api-report.md

@@ -11,6 +11,7 @@ import express from 'express';
 import { ExternalDependency } from '@backstage/plugin-devtools-common';
 import { Logger } from 'winston';
 import { PermissionEvaluator } from '@backstage/plugin-permission-common';
+import { SignalService } from '@backstage/plugin-signals-node';
 
 // @public (undocumented)
 export function createRouter(options: RouterOptions): Promise<express.Router>;
@@ -40,5 +41,7 @@ export interface RouterOptions {
   logger: Logger;
   // (undocumented)
   permissions: PermissionEvaluator;
+  // (undocumented)
+  signalService?: SignalService;
 }
 ```

plugins/devtools-backend/package.json

@@ -38,6 +38,7 @@
     "@backstage/plugin-devtools-common": "workspace:^",
     "@backstage/plugin-permission-common": "workspace:^",
     "@backstage/plugin-permission-node": "workspace:^",
+    "@backstage/plugin-signals-node": "workspace:^",
     "@backstage/types": "workspace:^",
     "@manypkg/get-packages": "^1.1.3",
     "@types/express": "*",

plugins/devtools-backend/src/service/router.ts

@@ -33,6 +33,7 @@ import { errorHandler } from '@backstage/backend-common';
 import express from 'express';
 import { getBearerTokenFromAuthorizationHeader } from '@backstage/plugin-auth-node';
 import { createPermissionIntegrationRouter } from '@backstage/plugin-permission-node';
+import { SignalService } from '@backstage/plugin-signals-node';
 
 /** @public */
 export interface RouterOptions {
@@ -40,17 +41,28 @@ export interface RouterOptions {
   logger: Logger;
   config: Config;
   permissions: PermissionEvaluator;
+  signalService?: SignalService;
 }
 
 /** @public */
 export async function createRouter(
   options: RouterOptions,
 ): Promise<express.Router> {
-  const { logger, config, permissions } = options;
+  const { logger, config, permissions, signalService } = options;
 
   const devToolsBackendApi =
     options.devToolsBackendApi || new DevToolsBackendApi(logger, config);
 
+  if (signalService) {
+    // Publish info periodically using the signal service
+    setInterval(async () => {
+      if (signalService.hasSubscribers('devtools:info')) {
+        const info = await devToolsBackendApi.listInfo();
+        await signalService.publish('*', 'devtools:info', info);
+      }
+    }, 5000);
+  }
+
   const router = Router();
   router.use(express.json());
   router.use(