Add custom error page for uncaught exceptions

remoteappmanager/application.py

@@ -111,8 +111,12 @@ def _db_default(self):
         class_path = self.file_config.accounting_class
         module_path, _, cls_name = class_path.rpartition('.')
         cls = getattr(importlib.import_module(module_path), cls_name)
-
-        return cls(**self.file_config.accounting_kwargs)
+        try:
+            return cls(**self.file_config.accounting_kwargs)
+        except Exception:
+            reason = 'The database is not initialised properly.'
+            self.log.exception(reason)
+            raise web.HTTPError(reason=reason)
 
     @default("user")
     def _user_default(self):

remoteappmanager/handlers/base_handler.py

@@ -1,3 +1,4 @@
+from http.client import responses
 from urllib.parse import urljoin
 
 from tornado import web, gen
@@ -40,3 +41,20 @@ def render(self, template_name, **kwargs):
 
         args.update(kwargs)
         super(BaseHandler, self).render(template_name, **args)
+
+    def write_error(self, status_code, **kwargs):
+        """Render error page for uncaught errors"""
+        status_message = responses.get(status_code, 'Unknown HTTP Error')
+        message = ""
+
+        # If this error was caused by an uncaught exception
+        # log exception message and reference number as well
+        exc_info = kwargs.get('exc_info')
+        if exc_info:
+            exception = exc_info[1]
+            ref = self.log.issue(status_message, exception)
+            reason = getattr(exception, 'reason', '')
+            message = '{} Ref.: {}'.format(reason, ref)
+
+        self.render('error.html', status_code=status_code,
+                    status_message=status_message, message=message)

remoteappmanager/templates/error.html

@@ -0,0 +1,28 @@
+{% extends "page.html" %}
+
+{% block login_widget %}
+{% endblock %}
+
+{% block main %}
+
+<div class="error">
+  {% block h1_error %}
+  <h1>
+    {{status_code}} : {{status_message}}
+  </h1>
+  {% endblock h1_error %}
+  {% block error_detail %}
+  {% if message %}
+  <p>
+    {{message}}
+  </p>
+  {% endif %}
+  {% if message_html %}
+  <p>
+    {{message_html | safe}}
+  </p>
+  {% endif %}
+  {% endblock error_detail %}
+</div>
+
+{% endblock %}

tests/handlers/test_base_handler.py

@@ -0,0 +1,85 @@
+import os
+
+from tests import utils
+from tests.mocking import dummy
+from tests.temp_mixin import TempMixin
+
+
+class TestBaseHandler(TempMixin, utils.AsyncHTTPTestCase):
+    def setUp(self):
+        self._old_proxy_api_token = os.environ.get("PROXY_API_TOKEN", None)
+        os.environ["PROXY_API_TOKEN"] = "dummy_token"
+
+        def cleanup():
+            if self._old_proxy_api_token is not None:
+                os.environ["PROXY_API_TOKEN"] = self._old_proxy_api_token
+            else:
+                del os.environ["PROXY_API_TOKEN"]
+
+        self.addCleanup(cleanup)
+
+        super().setUp()
+
+    def get_app(self):
+        file_config = dummy.FileConfig()
+        file_config.accounting_class = 'this_should_fail'
+        file_config.accounting_kwargs = {}
+
+        app = dummy.create_application(file_config=file_config)
+        app.hub.verify_token.return_value = {
+            'pending': None,
+            'name': app.settings['user'],
+            'admin': False,
+            'server': app.settings['base_urlpath']}
+        return app
+
+    def test_home_internal_error(self):
+        res = self.fetch("/user/username/",
+                         headers={
+                             "Cookie": "jupyter-hub-token-username=foo"
+                         }
+                         )
+
+        self.assertEqual(res.code, 500)
+        self.assertIn('Internal Server Error', str(res.body))
+        self.assertIn(" Ref.:", str(res.body))
+
+
+class TestBaseHandlerDatabaseError(TempMixin, utils.AsyncHTTPTestCase):
+    def setUp(self):
+        self._old_proxy_api_token = os.environ.get("PROXY_API_TOKEN", None)
+        os.environ["PROXY_API_TOKEN"] = "dummy_token"
+
+        def cleanup():
+            if self._old_proxy_api_token is not None:
+                os.environ["PROXY_API_TOKEN"] = self._old_proxy_api_token
+            else:
+                del os.environ["PROXY_API_TOKEN"]
+
+        self.addCleanup(cleanup)
+
+        super().setUp()
+
+    def get_app(self):
+        file_config = dummy.FileConfig()
+        file_config.accounting_kwargs = {}
+
+        app = dummy.create_application(file_config=file_config)
+        app.hub.verify_token.return_value = {
+            'pending': None,
+            'name': app.settings['user'],
+            'admin': False,
+            'server': app.settings['base_urlpath']}
+        return app
+
+    def test_home_internal_error(self):
+        res = self.fetch("/user/username/",
+                         headers={
+                             "Cookie": "jupyter-hub-token-username=foo"
+                         }
+                         )
+
+        self.assertEqual(res.code, 500)
+        self.assertIn('Internal Server Error', str(res.body))
+        self.assertIn("The database is not initialised properly. Ref.:",
+                      str(res.body))