prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  404 on single user notebook server anytime I restart jupyterhub
  I just deployed jupyterhub from scratch using my ansible scripts this morning. The script are unchanged from 2-3 weeks ago when I did it previously and it was all working. I am running from latest master of jupyterhub.
  
  Anytime I restart jupyterhub (hub+proxy) I see the following behavior:
  - I can log in (using GitHub OAuth)
  - Trying to start my server gives me a 404 on `/hub/users/ellisonbg`. I can tell from the server log that the single user server isn't being started.
  - I can go to the Admin page and start my server from there.
  - But then, I get a redirect loop when I try to go to my single user server.
  - If I clear all my cookies while my single user server (started through the Admin page) is still running, it starts to work as expected. I can start and stop the single user server on the control panel page just fine.
  - If a restart jupyterhub, the problems start all over again.
  
  I am using a fixed proxy_auth_token and cookie secret.
  
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `jupyterhub/handlers/pages.py`
  Content:
  ```
  1 """Basic html-rendering handlers."""
  2 
  3 # Copyright (c) Jupyter Development Team.
  4 # Distributed under the terms of the Modified BSD License.
  5 
  6 from tornado import web, gen
  7 
  8 from .. import orm
  9 from ..utils import admin_only, url_path_join
  10 from .base import BaseHandler
  11 from .login import LoginHandler
  12 
  13 
  14 class RootHandler(BaseHandler):
  15     """Render the Hub root page.
  16     
  17     If logged in, redirects to:
  18     
  19     - single-user server if running
  20     - hub home, otherwise
  21     
  22     Otherwise, renders login page.
  23     """
  24     def get(self):
  25         user = self.get_current_user()
  26         if user:
  27             if user.running:
  28                 url = user.server.base_url
  29                 self.log.debug("User is running: %s", url)
  30             else:
  31                 url = url_path_join(self.hub.server.base_url, 'home')
  32                 self.log.debug("User is not running: %s", url)
  33             self.redirect(url)
  34             return
  35         url = url_path_join(self.hub.server.base_url, 'login')
  36         self.redirect(url)
  37 
  38 
  39 class HomeHandler(BaseHandler):
  40     """Render the user's home page."""
  41 
  42     @web.authenticated
  43     def get(self):
  44         html = self.render_template('home.html',
  45             user=self.get_current_user(),
  46         )
  47         self.finish(html)
  48 
  49 
  50 class SpawnHandler(BaseHandler):
  51     """Handle spawning of single-user servers via form.
  52     
  53     GET renders the form, POST handles form submission.
  54     
  55     Only enabled when Spawner.options_form is defined.
  56     """
  57     @web.authenticated
  58     def get(self):
  59         """GET renders form for spawning with user-specified options"""
  60         user = self.get_current_user()
  61         if user.running:
  62             url = user.server.base_url
  63             self.log.debug("User is running: %s", url)
  64             self.redirect(url)
  65             return
  66         if user.spawner.options_form:
  67             html = self.render_template('spawn.html',
  68                 user=self.get_current_user(),
  69                 spawner_options_form=user.spawner.options_form,
  70             )
  71             self.finish(html)
  72         else:
  73             # not running, no form. Trigger spawn.
  74             url = url_path_join(self.base_url, 'users', user.name)
  75             self.redirect(url)
  76     
  77     @web.authenticated
  78     @gen.coroutine
  79     def post(self):
  80         """POST spawns with user-specified options"""
  81         user = self.get_current_user()
  82         if user.running:
  83             url = user.server.base_url
  84             self.log.warning("User is already running: %s", url)
  85             self.redirect(url)
  86             return
  87         form_options = {}
  88         for key, byte_list in self.request.body_arguments.items():
  89             form_options[key] = [ bs.decode('utf8') for bs in byte_list ]
  90         options = user.spawner.options_from_form(form_options)
  91         yield self.spawn_single_user(user, options=options)
  92         self.set_login_cookie(user)
  93         url = user.server.base_url
  94         self.redirect(url)
  95 
  96 class AdminHandler(BaseHandler):
  97     """Render the admin page."""
  98 
  99     @admin_only
  100     def get(self):
  101         available = {'name', 'admin', 'running', 'last_activity'}
  102         default_sort = ['admin', 'name']
  103         mapping = {
  104             'running': '_server_id'
  105         }
  106         default_order = {
  107             'name': 'asc',
  108             'last_activity': 'desc',
  109             'admin': 'desc',
  110             'running': 'desc',
  111         }
  112         sorts = self.get_arguments('sort') or default_sort
  113         orders = self.get_arguments('order')
  114         
  115         for bad in set(sorts).difference(available):
  116             self.log.warn("ignoring invalid sort: %r", bad)
  117             sorts.remove(bad)
  118         for bad in set(orders).difference({'asc', 'desc'}):
  119             self.log.warn("ignoring invalid order: %r", bad)
  120             orders.remove(bad)
  121         
  122         # add default sort as secondary
  123         for s in default_sort:
  124             if s not in sorts:
  125                 sorts.append(s)
  126         if len(orders) < len(sorts):
  127             for col in sorts[len(orders):]:
  128                 orders.append(default_order[col])
  129         else:
  130             orders = orders[:len(sorts)]
  131         
  132         # this could be one incomprehensible nested list comprehension
  133         # get User columns
  134         cols = [ getattr(orm.User, mapping.get(c, c)) for c in sorts ]
  135         # get User.col.desc() order objects
  136         ordered = [ getattr(c, o)() for c, o in zip(cols, orders) ]
  137         
  138         users = self.db.query(orm.User).order_by(*ordered)
  139         users = [ self._user_from_orm(u) for u in users ]
  140         running = [ u for u in users if u.running ]
  141         
  142         html = self.render_template('admin.html',
  143             user=self.get_current_user(),
  144             admin_access=self.settings.get('admin_access', False),
  145             users=users,
  146             running=running,
  147             sort={s:o for s,o in zip(sorts, orders)},
  148         )
  149         self.finish(html)
  150 
  151 
  152 default_handlers = [
  153     (r'/', RootHandler),
  154     (r'/home', HomeHandler),
  155     (r'/admin', AdminHandler),
  156     (r'/spawn', SpawnHandler),
  157 ]
  158
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/jupyterhub/handlers/pages.py b/jupyterhub/handlers/pages.py
  --- a/jupyterhub/handlers/pages.py
  +++ b/jupyterhub/handlers/pages.py
  @@ -71,7 +71,7 @@
               self.finish(html)
           else:
               # not running, no form. Trigger spawn.
  -            url = url_path_join(self.base_url, 'users', user.name)
  +            url = url_path_join(self.base_url, 'user', user.name)
               self.redirect(url)
       
       @web.authenticated
  
verification_info: {"golden_diff": "diff --git a/jupyterhub/handlers/pages.py b/jupyterhub/handlers/pages.py\n--- a/jupyterhub/handlers/pages.py\n+++ b/jupyterhub/handlers/pages.py\n@@ -71,7 +71,7 @@\n             self.finish(html)\n         else:\n             # not running, no form. Trigger spawn.\n-            url = url_path_join(self.base_url, 'users', user.name)\n+            url = url_path_join(self.base_url, 'user', user.name)\n             self.redirect(url)\n     \n     @web.authenticated\n", "issue": "404 on single user notebook server anytime I restart jupyterhub\nI just deployed jupyterhub from scratch using my ansible scripts this morning. The script are unchanged from 2-3 weeks ago when I did it previously and it was all working. I am running from latest master of jupyterhub.\n\nAnytime I restart jupyterhub (hub+proxy) I see the following behavior:\n- I can log in (using GitHub OAuth)\n- Trying to start my server gives me a 404 on `/hub/users/ellisonbg`. I can tell from the server log that the single user server isn't being started.\n- I can go to the Admin page and start my server from there.\n- But then, I get a redirect loop when I try to go to my single user server.\n- If I clear all my cookies while my single user server (started through the Admin page) is still running, it starts to work as expected. I can start and stop the single user server on the control panel page just fine.\n- If a restart jupyterhub, the problems start all over again.\n\nI am using a fixed proxy_auth_token and cookie secret.\n\n", "before_files": [{"content": "\"\"\"Basic html-rendering handlers.\"\"\"\n\n# Copyright (c) Jupyter Development Team.\n# Distributed under the terms of the Modified BSD License.\n\nfrom tornado import web, gen\n\nfrom .. import orm\nfrom ..utils import admin_only, url_path_join\nfrom .base import BaseHandler\nfrom .login import LoginHandler\n\n\nclass RootHandler(BaseHandler):\n    \"\"\"Render the Hub root page.\n    \n    If logged in, redirects to:\n    \n    - single-user server if running\n    - hub home, otherwise\n    \n    Otherwise, renders login page.\n    \"\"\"\n    def get(self):\n        user = self.get_current_user()\n        if user:\n            if user.running:\n                url = user.server.base_url\n                self.log.debug(\"User is running: %s\", url)\n            else:\n                url = url_path_join(self.hub.server.base_url, 'home')\n                self.log.debug(\"User is not running: %s\", url)\n            self.redirect(url)\n            return\n        url = url_path_join(self.hub.server.base_url, 'login')\n        self.redirect(url)\n\n\nclass HomeHandler(BaseHandler):\n    \"\"\"Render the user's home page.\"\"\"\n\n    @web.authenticated\n    def get(self):\n        html = self.render_template('home.html',\n            user=self.get_current_user(),\n        )\n        self.finish(html)\n\n\nclass SpawnHandler(BaseHandler):\n    \"\"\"Handle spawning of single-user servers via form.\n    \n    GET renders the form, POST handles form submission.\n    \n    Only enabled when Spawner.options_form is defined.\n    \"\"\"\n    @web.authenticated\n    def get(self):\n        \"\"\"GET renders form for spawning with user-specified options\"\"\"\n        user = self.get_current_user()\n        if user.running:\n            url = user.server.base_url\n            self.log.debug(\"User is running: %s\", url)\n            self.redirect(url)\n            return\n        if user.spawner.options_form:\n            html = self.render_template('spawn.html',\n                user=self.get_current_user(),\n                spawner_options_form=user.spawner.options_form,\n            )\n            self.finish(html)\n        else:\n            # not running, no form. Trigger spawn.\n            url = url_path_join(self.base_url, 'users', user.name)\n            self.redirect(url)\n    \n    @web.authenticated\n    @gen.coroutine\n    def post(self):\n        \"\"\"POST spawns with user-specified options\"\"\"\n        user = self.get_current_user()\n        if user.running:\n            url = user.server.base_url\n            self.log.warning(\"User is already running: %s\", url)\n            self.redirect(url)\n            return\n        form_options = {}\n        for key, byte_list in self.request.body_arguments.items():\n            form_options[key] = [ bs.decode('utf8') for bs in byte_list ]\n        options = user.spawner.options_from_form(form_options)\n        yield self.spawn_single_user(user, options=options)\n        self.set_login_cookie(user)\n        url = user.server.base_url\n        self.redirect(url)\n\nclass AdminHandler(BaseHandler):\n    \"\"\"Render the admin page.\"\"\"\n\n    @admin_only\n    def get(self):\n        available = {'name', 'admin', 'running', 'last_activity'}\n        default_sort = ['admin', 'name']\n        mapping = {\n            'running': '_server_id'\n        }\n        default_order = {\n            'name': 'asc',\n            'last_activity': 'desc',\n            'admin': 'desc',\n            'running': 'desc',\n        }\n        sorts = self.get_arguments('sort') or default_sort\n        orders = self.get_arguments('order')\n        \n        for bad in set(sorts).difference(available):\n            self.log.warn(\"ignoring invalid sort: %r\", bad)\n            sorts.remove(bad)\n        for bad in set(orders).difference({'asc', 'desc'}):\n            self.log.warn(\"ignoring invalid order: %r\", bad)\n            orders.remove(bad)\n        \n        # add default sort as secondary\n        for s in default_sort:\n            if s not in sorts:\n                sorts.append(s)\n        if len(orders) < len(sorts):\n            for col in sorts[len(orders):]:\n                orders.append(default_order[col])\n        else:\n            orders = orders[:len(sorts)]\n        \n        # this could be one incomprehensible nested list comprehension\n        # get User columns\n        cols = [ getattr(orm.User, mapping.get(c, c)) for c in sorts ]\n        # get User.col.desc() order objects\n        ordered = [ getattr(c, o)() for c, o in zip(cols, orders) ]\n        \n        users = self.db.query(orm.User).order_by(*ordered)\n        users = [ self._user_from_orm(u) for u in users ]\n        running = [ u for u in users if u.running ]\n        \n        html = self.render_template('admin.html',\n            user=self.get_current_user(),\n            admin_access=self.settings.get('admin_access', False),\n            users=users,\n            running=running,\n            sort={s:o for s,o in zip(sorts, orders)},\n        )\n        self.finish(html)\n\n\ndefault_handlers = [\n    (r'/', RootHandler),\n    (r'/home', HomeHandler),\n    (r'/admin', AdminHandler),\n    (r'/spawn', SpawnHandler),\n]\n", "path": "jupyterhub/handlers/pages.py"}], "after_files": [{"content": "\"\"\"Basic html-rendering handlers.\"\"\"\n\n# Copyright (c) Jupyter Development Team.\n# Distributed under the terms of the Modified BSD License.\n\nfrom tornado import web, gen\n\nfrom .. import orm\nfrom ..utils import admin_only, url_path_join\nfrom .base import BaseHandler\nfrom .login import LoginHandler\n\n\nclass RootHandler(BaseHandler):\n    \"\"\"Render the Hub root page.\n    \n    If logged in, redirects to:\n    \n    - single-user server if running\n    - hub home, otherwise\n    \n    Otherwise, renders login page.\n    \"\"\"\n    def get(self):\n        user = self.get_current_user()\n        if user:\n            if user.running:\n                url = user.server.base_url\n                self.log.debug(\"User is running: %s\", url)\n            else:\n                url = url_path_join(self.hub.server.base_url, 'home')\n                self.log.debug(\"User is not running: %s\", url)\n            self.redirect(url)\n            return\n        url = url_path_join(self.hub.server.base_url, 'login')\n        self.redirect(url)\n\n\nclass HomeHandler(BaseHandler):\n    \"\"\"Render the user's home page.\"\"\"\n\n    @web.authenticated\n    def get(self):\n        html = self.render_template('home.html',\n            user=self.get_current_user(),\n        )\n        self.finish(html)\n\n\nclass SpawnHandler(BaseHandler):\n    \"\"\"Handle spawning of single-user servers via form.\n    \n    GET renders the form, POST handles form submission.\n    \n    Only enabled when Spawner.options_form is defined.\n    \"\"\"\n    @web.authenticated\n    def get(self):\n        \"\"\"GET renders form for spawning with user-specified options\"\"\"\n        user = self.get_current_user()\n        if user.running:\n            url = user.server.base_url\n            self.log.debug(\"User is running: %s\", url)\n            self.redirect(url)\n            return\n        if user.spawner.options_form:\n            html = self.render_template('spawn.html',\n                user=self.get_current_user(),\n                spawner_options_form=user.spawner.options_form,\n            )\n            self.finish(html)\n        else:\n            # not running, no form. Trigger spawn.\n            url = url_path_join(self.base_url, 'user', user.name)\n            self.redirect(url)\n    \n    @web.authenticated\n    @gen.coroutine\n    def post(self):\n        \"\"\"POST spawns with user-specified options\"\"\"\n        user = self.get_current_user()\n        if user.running:\n            url = user.server.base_url\n            self.log.warning(\"User is already running: %s\", url)\n            self.redirect(url)\n            return\n        form_options = {}\n        for key, byte_list in self.request.body_arguments.items():\n            form_options[key] = [ bs.decode('utf8') for bs in byte_list ]\n        options = user.spawner.options_from_form(form_options)\n        yield self.spawn_single_user(user, options=options)\n        self.set_login_cookie(user)\n        url = user.server.base_url\n        self.redirect(url)\n\nclass AdminHandler(BaseHandler):\n    \"\"\"Render the admin page.\"\"\"\n\n    @admin_only\n    def get(self):\n        available = {'name', 'admin', 'running', 'last_activity'}\n        default_sort = ['admin', 'name']\n        mapping = {\n            'running': '_server_id'\n        }\n        default_order = {\n            'name': 'asc',\n            'last_activity': 'desc',\n            'admin': 'desc',\n            'running': 'desc',\n        }\n        sorts = self.get_arguments('sort') or default_sort\n        orders = self.get_arguments('order')\n        \n        for bad in set(sorts).difference(available):\n            self.log.warn(\"ignoring invalid sort: %r\", bad)\n            sorts.remove(bad)\n        for bad in set(orders).difference({'asc', 'desc'}):\n            self.log.warn(\"ignoring invalid order: %r\", bad)\n            orders.remove(bad)\n        \n        # add default sort as secondary\n        for s in default_sort:\n            if s not in sorts:\n                sorts.append(s)\n        if len(orders) < len(sorts):\n            for col in sorts[len(orders):]:\n                orders.append(default_order[col])\n        else:\n            orders = orders[:len(sorts)]\n        \n        # this could be one incomprehensible nested list comprehension\n        # get User columns\n        cols = [ getattr(orm.User, mapping.get(c, c)) for c in sorts ]\n        # get User.col.desc() order objects\n        ordered = [ getattr(c, o)() for c, o in zip(cols, orders) ]\n        \n        users = self.db.query(orm.User).order_by(*ordered)\n        users = [ self._user_from_orm(u) for u in users ]\n        running = [ u for u in users if u.running ]\n        \n        html = self.render_template('admin.html',\n            user=self.get_current_user(),\n            admin_access=self.settings.get('admin_access', False),\n            users=users,\n            running=running,\n            sort={s:o for s,o in zip(sorts, orders)},\n        )\n        self.finish(html)\n\n\ndefault_handlers = [\n    (r'/', RootHandler),\n    (r'/home', HomeHandler),\n    (r'/admin', AdminHandler),\n    (r'/spawn', SpawnHandler),\n]\n", "path": "jupyterhub/handlers/pages.py"}]}