DEV: Close transactions at the end of HTTP Requests.

Fixes #84

jupyterhub/app.py

@@ -262,6 +262,7 @@ class JupyterHubApp(Application):
         help="log all database transactions. This has A LOT of output"
     )
     db = Any()
+    session_factory = Any()
     
     admin_users = Set(config=True,
         help="""set of usernames of admin users
@@ -364,9 +365,13 @@ class JupyterHubApp(Application):
         """Create the database connection"""
         self.log.debug("Connecting to db: %s", self.db_url)
         try:
-            self.db = orm.new_session(self.db_url, reset=self.reset_db, echo=self.debug_db,
+            self.session_factory = orm.new_session_factory(
+                self.db_url,
+                reset=self.reset_db,
+                echo=self.debug_db,
                 **self.db_kwargs
             )
+            self.db = self.session_factory()
         except OperationalError as e:
             self.log.error("Failed to connect to db: %s", self.db_url)
             self.log.debug("Database error was:", exc_info=True)

jupyterhub/handlers/base.py

@@ -58,6 +58,11 @@ class BaseHandler(RequestHandler):
     def authenticator(self):
         return self.settings.get('authenticator', None)
 
+    def finish(self, *args, **kwargs):
+        """Roll back any uncommitted transactions from the handler."""
+        self.db.rollback()
+        super(BaseHandler, self).finish(*args, **kwargs)
+
     #---------------------------------------------------------------
     # Login and cookie-related
     #---------------------------------------------------------------

jupyterhub/orm.py

@@ -381,17 +381,20 @@ class CookieToken(Token, Base):
     __tablename__ = 'cookie_tokens'
 
 
-def new_session(url="sqlite:///:memory:", reset=False, **kwargs):
+def new_session_factory(url="sqlite:///:memory:", reset=False, **kwargs):
     """Create a new session at url"""
     if url.startswith('sqlite'):
         kwargs.setdefault('connect_args', {'check_same_thread': False})
-    kwargs.setdefault('poolclass', StaticPool)
+
+    if url.endswith(':memory:'):
+        # If we're using an in-memory database, ensure that only one connection
+        # is ever created.
+        kwargs.setdefault('poolclass', StaticPool)
+
     engine = create_engine(url, **kwargs)
-    Session = sessionmaker(bind=engine)
-    session = Session()
     if reset:
         Base.metadata.drop_all(engine)
     Base.metadata.create_all(engine)
-    return session
-
 
+    session_factory = sessionmaker(bind=engine)
+    return session_factory

jupyterhub/tests/conftest.py

@@ -22,7 +22,7 @@ def db():
     """Get a db session"""
     global _db
     if _db is None:
-        _db = orm.new_session('sqlite:///:memory:', echo=True)
+        _db = orm.new_session_factory('sqlite:///:memory:', echo=True)()
         user = orm.User(
             name=getuser_unicode(),
             server=orm.Server(),

jupyterhub/tests/mocking.py

@@ -1,5 +1,6 @@
 """mock utilities for testing"""
 
+import os
 import sys
 import threading
 
@@ -57,11 +58,18 @@ class MockPAMAuthenticator(PAMAuthenticator):
 class MockHubApp(JupyterHubApp):
     """HubApp with various mock bits"""
 
+    db_path = os.path.join(
+        os.path.dirname(
+            os.path.realpath(__file__),
+        ),
+        "test.sqlite",
+    )
+    
     def _ip_default(self):
         return 'localhost'
     
     def _db_url_default(self):
-        return 'sqlite:///:memory:'
+        return "sqlite:///" + self.db_path
 
     def _authenticator_class_default(self):
         return MockPAMAuthenticator
@@ -72,7 +80,12 @@ class MockHubApp(JupyterHubApp):
     def _admin_users_default(self):
         return {'admin'}
 
+    def rm_db(self):
+        if os.path.exists(self.db_path):
+            os.remove(self.db_path)
+
     def start(self, argv=None):
+        self.rm_db()
         evt = threading.Event()
         def _start():
             self.io_loop = IOLoop.current()
@@ -91,6 +104,6 @@ class MockHubApp(JupyterHubApp):
         evt.wait(timeout=5)
     
     def stop(self):
+        self.rm_db()
         self.io_loop.add_callback(self.io_loop.stop)
         self._thread.join()
-

jupyterhub/tests/test_api.py

@@ -7,6 +7,30 @@ import requests
 from ..utils import url_path_join as ujoin
 from .. import orm
 
+
+def check_db_locks(func):
+    """
+    Decorator for test functions that verifies no locks are held on the
+    application's database upon exit by creating and dropping a dummy table.
+
+    Relies on an instance of JupyterhubApp being the first argument to the
+    decorated function.
+    """
+
+    def new_func(*args, **kwargs):
+        retval = func(*args, **kwargs)
+
+        app = args[0]
+        temp_session = app.session_factory()
+        temp_session.execute('CREATE TABLE dummy (foo INT)')
+        temp_session.execute('DROP TABLE dummy')
+        temp_session.close()
+
+        return retval
+
+    return new_func
+
+
 def find_user(db, name):
     return db.query(orm.User).filter(orm.User.name==name).first()
     
@@ -28,6 +52,7 @@ def auth_header(db, name):
         token = user.api_tokens[0]
     return {'Authorization': 'token %s' % token.token}
 
+@check_db_locks
 def api_request(app, *api_path, **kwargs):
     """Make an API request"""
     base_url = app.hub.server.url
@@ -71,7 +96,6 @@ def test_auth_api(app):
     )
     assert r.status_code == 403
 
-
 def test_get_users(app):
     db = app.db
     r = api_request(app, 'users')
@@ -179,4 +203,3 @@ def test_spawn(app, io_loop):
     assert 'pid' not in user.state
     status = io_loop.run_sync(user.spawner.poll)
     assert status == 0
-