compare hub and single-user server versions

in both directions - Hub checks singleuser server on spawn and singleuser server checks Hub on startup

if minor versions mismatch, log at warning level, otherwise debug

jupyterhub/__init__.py

@@ -1 +1 @@
-from .version import version_info, __version__
+from ._version import version_info, __version__

jupyterhub/_version.py

@@ -0,0 +1,40 @@
+"""JupyterHub version info"""
+
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+version_info = (
+    0,
+    8,
+    0,
+    'dev',
+)
+
+__version__ = '.'.join(map(str, version_info))
+
+
+def _check_version(hub_version, singleuser_version, log):
+    """Compare Hub and single-user server versions"""
+    if not hub_version:
+        log.warning("Hub has no version header, which means it is likely < 0.8. Expected %s", __version__)
+        return
+
+    if not singleuser_version:
+        log.warning("Single-user server has no version header, which means it is likely < 0.8. Expected %s", __version__)
+        return
+
+    # compare minor X.Y versions
+    if hub_version != singleuser_version:
+        from distutils.version import LooseVersion as V
+        hub_major_minor = V(hub_version).version[:2]
+        singleuser_major_minor = V(__version__).version[:2]
+        if singleuser_major_minor == hub_major_minor:
+            # patch-level mismatch or lower, log difference at debug-level
+            # because this should be fine
+            log_method = log.debug
+        else:
+            # log warning-level for more significant mismatch, such as 0.8 vs 0.9, etc.
+            log_method = log.warning
+        log_method("jupyterhub version %s != jupyterhub-singleuser version %s",
+            hub_version, __version__,
+        )

jupyterhub/apihandlers/hub.py

@@ -11,7 +11,7 @@ from tornado.ioloop import IOLoop
 
 from ..utils import admin_only
 from .base import APIHandler
-from ..version import __version__
+from .._version import __version__
 
 
 class ShutdownAPIHandler(APIHandler):

jupyterhub/singleuser.py

@@ -4,12 +4,16 @@
 # Copyright (c) Jupyter Development Team.
 # Distributed under the terms of the Modified BSD License.
 
+from distutils.version import LooseVersion as V
 import os
+import re
 from textwrap import dedent
 from urllib.parse import urlparse
 
 from jinja2 import ChoiceLoader, FunctionLoader
 
+from tornado.httpclient import AsyncHTTPClient
+from tornado import gen
 from tornado import ioloop
 from tornado.web import HTTPError
 
@@ -37,7 +41,7 @@ from notebook.auth.login import LoginHandler
 from notebook.auth.logout import LogoutHandler
 from notebook.base.handlers import IPythonHandler
 
-from jupyterhub import __version__
+from ._version import __version__, _check_version
 from .log import log_request
 from .services.auth import HubOAuth, HubOAuthenticated, HubOAuthCallbackHandler
 from .utils import url_path_join
@@ -337,7 +341,27 @@ class SingleUserNotebookApp(NotebookApp):
             path = list(_exclude_home(path))
         return path
 
+    @gen.coroutine
+    def check_hub_version(self):
+        """Test a connection to my Hub
+        
+        - exit if I can't connect at all
+        - check version and warn on sufficient mismatch
+        """
+        client = AsyncHTTPClient()
+        try:
+            resp = yield client.fetch(self.hub_api_url)
+        except Exception:
+            self.log.exception("Failed to connect to my Hub at %s. Is it running?", self.hub_api_url)
+            self.exit(1)
+        
+        hub_version = resp.headers.get('X-JupyterHub-Version')
+        _check_version(hub_version, __version__, self.log)
+
     def start(self):
+        self.log.info("Starting jupyterhub-singleuser server version %s", __version__)
+        # start by hitting Hub to check version
+        ioloop.IOLoop.current().run_sync(self.check_hub_version)
         super(SingleUserNotebookApp, self).start()
 
     def init_hub_auth(self):

jupyterhub/user.py

@@ -12,6 +12,7 @@ from tornado.log import app_log
 from .utils import url_path_join, default_server_name
 
 from . import orm
+from ._version import _check_version, __version__
 from .objects import Server
 from traitlets import HasTraits, Any, Dict, observe, default
 from .spawner import LocalProcessSpawner
@@ -328,7 +329,7 @@ class User(HasTraits):
         db.commit()
         self.waiting_for_response = True
         try:
-            yield server.wait_up(http=True, timeout=spawner.http_timeout)
+            resp = yield server.wait_up(http=True, timeout=spawner.http_timeout)
         except Exception as e:
             if isinstance(e, TimeoutError):
                 self.log.warning(
@@ -353,6 +354,9 @@ class User(HasTraits):
                 ), exc_info=True)
             # raise original TimeoutError
             raise e
+        else:
+            server_version = resp.headers.get('X-JupyterHub-Version')
+            _check_version(__version__, server_version, self.log)
         finally:
             self.waiting_for_response = False
             self.spawn_pending = False

jupyterhub/version.py

@@ -1,13 +0,0 @@
-"""JupyterHub version info"""
-
-# Copyright (c) Jupyter Development Team.
-# Distributed under the terms of the Modified BSD License.
-
-version_info = (
-    0,
-    8,
-    0,
-    'dev',
-)
-
-__version__ = '.'.join(map(str, version_info))