add jupyterhub upgrade-db entry point

don't do automatic upgrades (yet)

I'm not sure if auto upgrades are a good idea or not.

jupyterhub/app.py

@@ -46,7 +46,7 @@ import jupyterhub
 from . import handlers, apihandlers
 from .handlers.static import CacheControlStaticFilesHandler, LogoHandler
 
-from . import orm
+from . import dbutil, orm
 from .user import User, UserDict
 from ._data import DATA_FILES_PATH
 from .log import CoroutineLogFormatter, log_request
@@ -103,6 +103,7 @@ SECRET_BYTES = 2048 # the number of bytes to use when generating new secrets
 class NewToken(Application):
     """Generate and print a new API token"""
     name = 'jupyterhub-token'
+    version = jupyterhub.__version__
     description = """Generate and return new API token for a user.
 
     Usage:
@@ -142,6 +143,26 @@ class NewToken(Application):
         token = user.new_api_token()
         print(token)
 
+class UpgradeDB(Application):
+    """Upgrade the JupyterHub database schema."""
+    
+    name = 'jupyterhub-upgrade-db'
+    version = jupyterhub.__version__
+    description = """Upgrade the JupyterHub database to the current schema.
+    
+    Usage:
+
+        jupyterhub upgrade-db
+    """
+    aliases = common_aliases
+    classes = []
+    
+    def start(self):
+        hub = JupyterHub(parent=self)
+        hub.load_config_file(hub.config_file)
+        self.log.info("Upgrading %s", hub.db_url)
+        dbutil.upgrade(hub.db_url)
+
 
 class JupyterHub(Application):
     """An Application for starting a Multi-User Jupyter Notebook server."""
@@ -170,7 +191,8 @@ class JupyterHub(Application):
     flags = Dict(flags)
 
     subcommands = {
-        'token': (NewToken, "Generate an API token for a user")
+        'token': (NewToken, "Generate an API token for a user"),
+        'upgrade-db': (UpgradeDB, "Upgrade your JupyterHub state database to the current version."),
     }
 
     classes = List([
@@ -706,6 +728,11 @@ class JupyterHub(Application):
             self.log.debug("Database error was:", exc_info=True)
             if self.db_url.startswith('sqlite:///'):
                 self._check_db_path(self.db_url.split(':///', 1)[1])
+            self.log.critical('\n'.join([
+                "If you recently upgraded JupyterHub, try running",
+                "    jupyterhub upgrade-db",
+                "to upgrade your JupyterHub database schema",
+            ]))
             self.exit(1)
 
     def init_hub(self):
@@ -1307,6 +1334,7 @@ class JupyterHub(Application):
             print("\nInterrupted")
 
 NewToken.classes.append(JupyterHub)
+UpgradeDB.classes.append(JupyterHub)
 
 main = JupyterHub.launch_instance
 

jupyterhub/dbutil.py

@@ -0,0 +1,82 @@
+"""Database utilities for JupyterHub"""
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+# Based on pgcontents.utils.migrate, used under the Apache license.
+
+from contextlib import contextmanager
+import os
+from subprocess import check_call
+import sys
+from tempfile import TemporaryDirectory
+
+_here = os.path.abspath(os.path.dirname(__file__))
+
+ALEMBIC_INI_TEMPLATE_PATH = os.path.join(_here, 'alembic.ini')
+ALEMBIC_DIR = os.path.join(_here, 'alembic')
+
+
+def write_alembic_ini(alembic_ini='alembic.ini', db_url='sqlite:///jupyterhub.sqlite'):
+    """Write a complete alembic.ini from our template.
+    
+    Parameters
+    ----------
+    
+    alembic_ini: str
+        path to the alembic.ini file that should be written.
+    db_url: str
+        The SQLAlchemy database url, e.g. `sqlite:///jupyterhub.sqlite`.
+    """
+    with open(ALEMBIC_INI_TEMPLATE_PATH) as f:
+        alembic_ini_tpl = f.read()
+    
+    with open(alembic_ini, 'w') as f:
+        f.write(
+            alembic_ini_tpl.format(
+                alembic_dir=ALEMBIC_DIR,
+                db_url=db_url,
+            )
+        )
+    
+
+
+@contextmanager
+def _temp_alembic_ini(db_url):
+    """Context manager for temporary JupyterHub alembic directory
+    
+    Temporarily write an alembic.ini file for use with alembic migration scripts.
+    
+    Context manager yields alembic.ini path.
+    
+    Parameters
+    ----------
+    
+    db_url: str
+        The SQLAlchemy database url, e.g. `sqlite:///jupyterhub.sqlite`.
+    
+    Returns
+    -------
+    
+    alembic_ini: str
+        The path to the temporary alembic.ini that we have created.
+        This file will be cleaned up on exit from the context manager.
+    """
+    with TemporaryDirectory() as td:
+        alembic_ini = os.path.join(td, 'alembic.ini')
+        write_alembic_ini(alembic_ini)
+        yield alembic_ini
+
+
+def upgrade(db_url, revision='head'):
+    """Upgrade the given database to revision.
+    
+    db_url: str
+        The SQLAlchemy database url, e.g. `sqlite:///jupyterhub.sqlite`.
+    revision: str [default: head]
+        The alembic revision to upgrade to.
+    """
+    with _temp_alembic_ini(db_url) as alembic_ini:
+        check_call(
+            ['alembic', '-c', alembic_ini, 'upgrade', revision]
+        )
+