Add ping method

deno-runtime/main.ts

@@ -28,6 +28,7 @@ type Handlers = {
     slashcommand: typeof slashcommandHandler;
     videoconference: typeof videoConferenceHandler;
     scheduler: typeof handleScheduler;
+    ping: (method: string, params: unknown) => 'pong';
 };
 
 async function requestRouter({ type, payload }: Messenger.JsonRpcRequest): Promise<void> {
@@ -37,6 +38,7 @@ async function requestRouter({ type, payload }: Messenger.JsonRpcRequest): Promi
         slashcommand: slashcommandHandler,
         videoconference: videoConferenceHandler,
         scheduler: handleScheduler,
+        ping: (_method, _params) => 'pong',
     };
 
     // We're not handling notifications at the moment

src/server/runtime/deno/AppsEngineDenoRuntime.ts

@@ -125,6 +125,14 @@ export class DenoRuntimeSubprocessController extends EventEmitter {
             this.deno = child_process.spawn(denoExePath, options);
 
             this.setupListeners();
+            this.startPing();
+
+            queueMicrotask(() => {
+                if (this.deno.exitCode !== null) {
+                    this.state = 'invalid';
+                    this.debug('Deno subprocess exited with code %d, signal %s', this.deno.exitCode, this.deno.signalCode);
+                }
+            });
         } catch (e) {
             this.state = 'invalid';
             console.error('Failed to start Deno subprocess', e);
@@ -137,6 +145,24 @@ export class DenoRuntimeSubprocessController extends EventEmitter {
         this.runtimeManager = manager.getRuntime();
     }
 
+    private startPing() {
+        const ping = () => {
+            const start = Date.now();
+            this.sendRequest({ method: 'ping', params: [] })
+                .then((result) => {
+                    if (result !== 'pong') {
+                        this.debug(`Expected 'pong', got %s (%d ms)`, result, Date.now() - start);
+                    }
+                })
+                .catch((reason: unknown) => {
+                    this.debug('Ping failed: %s (%d ms)', reason, Date.now() - start);
+                });
+        };
+
+        ping();
+        setInterval(ping, 5000);
+    }
+
     // Debug purposes, could be deleted later
     emit(eventName: string | symbol, ...args: any[]): boolean {
         const hadListeners = super.emit(eventName, ...args);