Merge pull request #6558 from jhamrick/kernel-start-failure

Handle kernel start failures more gracefully

IPython/html/services/sessions/handlers.py

@@ -10,6 +10,7 @@ from tornado import web
 from ...base.handlers import IPythonHandler, json_errors
 from IPython.utils.jsonutil import date_default
 from IPython.html.utils import url_path_join, url_escape
+from IPython.kernel.kernelspec import NoSuchKernel
 
 
 class SessionRootHandler(IPythonHandler):
@@ -52,7 +53,17 @@ class SessionRootHandler(IPythonHandler):
         if sm.session_exists(name=name, path=path):
             model = sm.get_session(name=name, path=path)
         else:
-            model = sm.create_session(name=name, path=path, kernel_name=kernel_name)
+            try:
+                model = sm.create_session(name=name, path=path, kernel_name=kernel_name)
+            except NoSuchKernel:
+                msg = ("The '%s' kernel is not available. Please pick another "
+                       "suitable kernel instead, or install that kernel." % kernel_name)
+                status_msg = '%s not found' % kernel_name
+                self.log.warn('Kernel not found: %s' % kernel_name)
+                self.set_status(501)
+                self.finish(json.dumps(dict(message=msg, short_message=status_msg)))
+                return
+
         location = url_path_join(self.base_url, 'api', 'sessions', model['id'])
         self.set_header('Location', url_escape(location))
         self.set_status(201)

IPython/html/static/notebook/js/notificationarea.js

@@ -159,7 +159,7 @@ define([
             });
         });
 
-        this.events.on('status_dead.Kernel',function () {
+        this.events.on('status_restart_failed.Kernel',function () {
             var msg = 'The kernel has died, and the automatic restart has failed.' +
                 ' It is possible the kernel cannot be restarted.' +
                 ' If you are not able to restart the kernel, you will still be able to save' +
@@ -184,6 +184,47 @@ define([
             });
         });
 
+        this.events.on('start_failed.Session',function (session, xhr, status, error) {
+            var full = status.responseJSON.message;
+            var short = status.responseJSON.short_message || 'Kernel error';
+            var traceback = status.responseJSON.traceback;
+
+            var showMsg = function () {
+                var msg = $('<div/>').append($('<p/>').text(full));
+                var cm, cm_elem;
+
+                if (traceback) {
+                    cm_elem = $('<div/>')
+                        .css('margin-top', '1em')
+                        .css('padding', '1em')
+                        .addClass('output_scroll');
+                    msg.append(cm_elem);
+                    cm = CodeMirror(cm_elem.get(0), {
+                        mode:  "python",
+                        readOnly : true
+                    });
+                    cm.setValue(traceback);
+                }
+
+                dialog.modal({
+                    title: "Failed to start the kernel",
+                    body : msg,
+                    keyboard_manager: that.keyboard_manager,
+                    notebook: that.notebook,
+                    open: $.proxy(cm.refresh, cm),
+                    buttons : {
+                        "Ok": { class: 'btn-primary' }
+                    }
+                });
+
+                return false;
+            };
+
+            that.save_widget.update_document_title();
+            $kernel_ind_icon.attr('class','kernel_dead_icon').attr('title','Kernel Dead');
+            knw.danger(short, undefined, showMsg);
+        });
+
         this.events.on('websocket_closed.Kernel', function (event, data) {
             var kernel = data.kernel;
             var ws_url = data.ws_url;

IPython/html/static/services/kernels/js/kernel.js

@@ -560,6 +560,7 @@ define([
         } else if (execution_state === 'dead') {
             this.stop_channels();
             this.events.trigger('status_dead.Kernel', {kernel: this});
+            this.events.trigger('status_restart_failed.Kernel', {kernel: this});
         }
     };
     

IPython/html/static/services/sessions/js/session.js

@@ -112,7 +112,6 @@ define([
 
     Session.prototype._handle_start_failure = function (xhr, status, error) {
         this.events.trigger('start_failed.Session', [this, xhr, status, error]);
-        this.events.trigger('status_dead.Kernel');
     };
     
     /**