Fix orphaned python processes on exit

backend/src/server_host.py

@@ -307,6 +307,12 @@ async def setup_sse(request: Request):
             break
 
 
+@app.post("/shutdown")
+async def shutdown(request: Request):
+    await close_server(request.app)
+    return json(success_response())
+
+
 async def import_packages(
     config: ServerConfig,
     update_progress_cb: UpdateProgressFn,

backend/src/server_process_helper.py

@@ -47,19 +47,25 @@ def __init__(self, flags: list[str]):
         self._stop_event = threading.Event()
 
         # Create a separate thread to read and print the output of the subprocess
-        threading.Thread(
+        self._reader_thread = threading.Thread(
             target=self._read_output,
             daemon=True,
             name="output reader",
-        ).start()
+        )
+        self._reader_thread.daemon = True
+        self._reader_thread.start()
 
     def close(self):
+        logger.info("Closing worker process...")
         self._stop_event.set()
-        self._process.terminate()
-        self._process.kill()
+        if self._process is not None:
+            self._process.terminate()
+            self._process.kill()
+            self._process = None
+            self._reader_thread = None
 
     def _read_output(self):
-        if self._process.stdout is None:
+        if self._process is None or self._process.stdout is None:
             return
         for line in self._process.stdout:
             if self._stop_event.is_set():

src/common/Backend.ts

@@ -255,6 +255,10 @@ export class Backend {
             package: pkg.id,
         });
     }
+
+    shutdown(): Promise<void> {
+        return this.fetchJson('/shutdown', 'POST');
+    }
 }
 
 const backendCache = new Map<string, Backend>();

src/main/backend/process.ts

@@ -111,6 +111,10 @@ export class OwnedBackendProcess implements BaseBackendProcess {
         this.errorListeners.push(listener);
     }
 
+    clearErrorListeners() {
+        this.errorListeners = [];
+    }
+
     private setNewProcess(process: ChildProcessWithoutNullStreams): void {
         this.process = process;
 
@@ -136,9 +140,9 @@ export class OwnedBackendProcess implements BaseBackendProcess {
     /**
      * Kills the current backend process.
      *
-     * @throws If the backend process could n
+     * @throws If the backend process couldn't exit
      */
-    kill() {
+    async kill() {
         log.info('Attempting to kill backend...');
 
         if (!this.process) {
@@ -153,11 +157,10 @@ export class OwnedBackendProcess implements BaseBackendProcess {
             return;
         }
 
+        await getBackend(this.url).shutdown();
         if (this.process.kill()) {
             this.process = undefined;
             log.info('Successfully killed backend.');
-        } else {
-            throw new Error('Unable to the backend process. Kill returned false.');
         }
     }
 
@@ -166,16 +169,16 @@ export class OwnedBackendProcess implements BaseBackendProcess {
      *
      * This function is guaranteed to throw no errors, it will only log errors if any occur.
      */
-    tryKill() {
+    async tryKill() {
         try {
-            this.kill();
+            await this.kill();
         } catch (error) {
             log.error('Error killing backend.', error);
         }
     }
 
-    restart() {
-        this.tryKill();
+    async restart() {
+        await this.tryKill();
 
         const backend = OwnedBackendProcess.spawnProcess(this.port, this.python, this.env);
         this.setNewProcess(backend);

src/main/gui/main-window.ts

@@ -257,12 +257,15 @@ const registerEventHandlerPostSetup = (
             app.exit(1);
         });
 
-        app.on('before-quit', () => backend.tryKill());
+        app.on('before-quit', () => {
+            backend.clearErrorListeners();
+            backend.tryKill().catch(log.error);
+        });
     }
 
-    ipcMain.handle('restart-backend', () => {
+    ipcMain.handle('restart-backend', async () => {
         if (backend.owned) {
-            backend.restart();
+            await backend.restart();
         } else {
             log.warn('Tried to restart non-owned backend');
         }
@@ -281,10 +284,14 @@ const registerEventHandlerPostSetup = (
 
     const restartChainner = (): void => {
         if (backend.owned) {
-            backend.tryKill();
+            backend
+                .tryKill()
+                .finally(() => {
+                    app.relaunch();
+                    app.exit();
+                })
+                .catch(log.error);
         }
-        app.relaunch();
-        app.exit();
     };
 
     ipcMain.on('reboot-after-save', () => {