Notify the user when a notebook kernel autorestarts

package.json

@@ -26,7 +26,7 @@
     "clean:src": "jlpm run clean",
     "clean:test": "lerna run clean --scope \"@jupyterlab/test-*\"",
     "clean:utils": "cd buildutils && jlpm run clean",
-    "coverage": "lerna run coverage --scope \"@jupyterlab/test-*\" --stream --concurrency 1",
+    "coverage": "lerna run coverage --scope \"@jupyterlab/test-*\" --stream --concurrency 1 --no-bail",
     "create:package": "node buildutils/lib/create-package.js",
     "create:test": "node buildutils/lib/create-test-package.js",
     "create:theme": "node buildutils/lib/create-theme.js",

packages/apputils/src/clientsession.tsx

@@ -878,26 +878,25 @@ export namespace ClientSession {
    *
    * Returns a promise resolving with whether the kernel was restarted.
    */
-  export function restartKernel(
+  export async function restartKernel(
     kernel: Kernel.IKernelConnection
   ): Promise<boolean> {
     let restartBtn = Dialog.warnButton({ label: 'RESTART ' });
-    return showDialog({
+    const result = await showDialog({
       title: 'Restart Kernel?',
       body:
         'Do you want to restart the current kernel? All variables will be lost.',
       buttons: [Dialog.cancelButton(), restartBtn]
-    }).then(result => {
-      if (kernel.isDisposed) {
-        return Promise.resolve(false);
-      }
-      if (result.button.accept) {
-        return kernel.restart().then(() => {
-          return true;
-        });
-      }
-      return false;
     });
+
+    if (kernel.isDisposed) {
+      return false;
+    }
+    if (result.button.accept) {
+      await kernel.restart();
+      return true;
+    }
+    return false;
   }
 
   /**

packages/apputils/src/toolbar.tsx

@@ -3,6 +3,8 @@
 
 import { UseSignal, ReactWidget } from './vdom';
 
+import { Kernel } from '@jupyterlab/services';
+
 import { Button } from '@jupyterlab/ui-components';
 
 import { IIterator, find, map, some } from '@phosphor/algorithm';
@@ -400,8 +402,7 @@ export namespace Toolbar {
    * Create a kernel status indicator item.
    *
    * #### Notes
-   * It show display a busy status if the kernel status is
-   * not idle.
+   * It will show a busy status if the kernel status is busy.
    * It will show the current status in the node title.
    * It can handle a change to the context or the kernel.
    */
@@ -679,10 +680,20 @@ namespace Private {
         return;
       }
       let status = session.status;
-      this.toggleClass(TOOLBAR_IDLE_CLASS, status === 'idle');
-      this.toggleClass(TOOLBAR_BUSY_CLASS, status !== 'idle');
+      const busy = this._isBusy(status);
+      this.toggleClass(TOOLBAR_BUSY_CLASS, busy);
+      this.toggleClass(TOOLBAR_IDLE_CLASS, !busy);
       let title = 'Kernel ' + status[0].toUpperCase() + status.slice(1);
       this.node.title = title;
     }
+
+    /**
+     * Check if status should be shown as busy.
+     */
+    private _isBusy(status: Kernel.Status): boolean {
+      return (
+        status === 'busy' || status === 'starting' || status === 'restarting'
+      );
+    }
   }
 }

packages/console/src/widget.ts

@@ -784,8 +784,7 @@ export class CodeConsole extends Widget {
       if (!kernel) {
         return;
       }
-      kernel
-        .requestKernelInfo()
+      kernel.ready
         .then(() => {
           if (this.isDisposed || !kernel || !kernel.info) {
             return;
@@ -797,6 +796,7 @@ export class CodeConsole extends Widget {
         });
     } else if (this.session.status === 'restarting') {
       this.addBanner();
+      this._handleInfo(this.session.kernel.info);
     }
   }
 

packages/notebook/src/panel.ts

@@ -9,7 +9,12 @@ import { Message } from '@phosphor/messaging';
 
 import { ISignal, Signal } from '@phosphor/signaling';
 
-import { IClientSession, Printing } from '@jupyterlab/apputils';
+import {
+  IClientSession,
+  Printing,
+  showDialog,
+  Dialog
+} from '@jupyterlab/apputils';
 
 import { DocumentWidget } from '@jupyterlab/docregistry';
 
@@ -51,6 +56,10 @@ export class NotebookPanel extends DocumentWidget<Notebook, INotebookModel> {
     // Set up things related to the context
     this.content.model = this.context.model;
     this.context.session.kernelChanged.connect(this._onKernelChanged, this);
+    this.context.session.statusChanged.connect(
+      this._onSessionStatusChanged,
+      this
+    );
 
     void this.revealed.then(() => {
       // Set the document edit mode on initial open if it looks like a new document.
@@ -184,13 +193,40 @@ export class NotebookPanel extends DocumentWidget<Notebook, INotebookModel> {
     }
     let { newValue } = args;
     void newValue.ready.then(() => {
-      if (this.model) {
+      if (this.model && this.context.session.kernel === newValue) {
         this._updateLanguage(newValue.info.language_info);
       }
     });
     void this._updateSpec(newValue);
   }
 
+  private _onSessionStatusChanged(
+    sender: IClientSession,
+    status: Kernel.Status
+  ) {
+    // If the status is autorestarting, and we aren't already in a series of
+    // autorestarts, show the dialog.
+    if (status === 'autorestarting' && !this._autorestarting) {
+      // The kernel died and the server is restarting it. We notify the user so
+      // they know why their kernel state is gone.
+      void showDialog({
+        title: 'Kernel Restarting',
+        body: `The kernel for ${
+          this.session.path
+        } appears to have died. It will restart automatically.`,
+        buttons: [Dialog.okButton()]
+      });
+      this._autorestarting = true;
+    } else if (status === 'restarting') {
+      // Another autorestart attempt will first change the status to
+      // restarting, then to autorestarting again, so we don't reset the
+      // autorestarting status if the status is 'restarting'.
+      /* no-op */
+    } else {
+      this._autorestarting = false;
+    }
+  }
+
   /**
    * Update the kernel language.
    */
@@ -215,6 +251,12 @@ export class NotebookPanel extends DocumentWidget<Notebook, INotebookModel> {
   }
 
   private _activated = new Signal<this, void>(this);
+
+  /**
+   * Whether we are currently in a series of autorestarts we have already
+   * notified the user about.
+   */
+  private _autorestarting = false;
 }
 
 /**