- In ``bfg_routesalchemy``, ``bfg_alchemy`` and ``bfgwiki2`` tutorial,

  clean up the SQLAlchemy connection by registering a
  ``repoze.tm.after_end`` callback instead of relying on a ``__del__``
  method of a ``Cleanup`` class added to the WSFI environment.  The
  ``__del__`` strategy was fragile and caused problems in the wild.
  Thanks to Daniel Holth for testing.

5 files changed, 43 insertions, 46 deletions

diff --git a/docs/tutorials/bfgwiki2/basiclayout.rst b/docs/tutorials/bfgwiki2/basiclayout.rst
index 5392660da..d30d919c1 100644
--- a/docs/tutorials/bfgwiki2/basiclayout.rst
+++ b/docs/tutorials/bfgwiki2/basiclayout.rst
@@ -119,26 +119,21 @@ function within the file named ``run.py``:
       :linenos:
       :language: py
 
-#. *Lines 1-4*. Imports to support later code.
+#. *Lines 1-8*. Imports to support later code.
 
-#. *Lines 6-10*.  We define a ``Cleanup`` class which has a
-   ``__del__`` method (the method called at Python object
-   destruction), which calls a function.
+#. *Lines 10-14*.  An event :term:`subscriber` which performs cleanup
+   at transaction boundaries.  As a result of registering this event
+   subscriber, after the current transaction is committed or aborted,
+   our database connection will be removed.
 
-#. *Lines 12-14*.  An event :term:`subscriber` which adds a
-   ``Cleanup`` instance to the WSGI environment as
-   ``tutorial.sasession``.  As a result of registering this event
-   subscriber, when the WSGI environment is cleaned up, our database
-   connection will be removed.
-
-#. *Lines 21-23*. Get the database configuration string from the
+#. *Lines 22-25*. Get the database configuration string from the
    ``tutorial.ini`` file's ``[app:sql]`` section.  This will be a URI
    (something like ``sqlite://``).
 
-#. Line *24*. We initialize our SQL database using SQLAlchemy, passing
+#. Line *26*. We initialize our SQL database using SQLAlchemy, passing
    it the db string.
 
-#. *Line 25*.  We construct a :term:`Configurator`.  The first
+#. *Line 27*.  We construct a :term:`Configurator`.  The first
    argument provided to the configurator is the :term:`root factory`,
    which is used by the :mod:`repoze.bfg` :term:`traversal` mechanism.
    Since this is a URL dispatch application, the root factory is
@@ -146,7 +141,7 @@ function within the file named ``run.py``:
    argument.  It contains a dictionary of settings parsed by
    PasteDeploy.
 
-#. *Lines 26-29*.  We then load a ZCML file to do application
+#. *Lines 28-31*.  We then load a ZCML file to do application
    configuration, and use the
    :meth:`repoze.bfg.configuration.Configurator.make_wsgi_app` method
    to return a :term:`WSGI` application.
diff --git a/docs/tutorials/bfgwiki2/src/authorization/tutorial/run.py b/docs/tutorials/bfgwiki2/src/authorization/tutorial/run.py
index 2506ca939..2e38bd29b 100644
--- a/docs/tutorials/bfgwiki2/src/authorization/tutorial/run.py
+++ b/docs/tutorials/bfgwiki2/src/authorization/tutorial/run.py
@@ -1,18 +1,18 @@
+import transaction
+
 from repoze.bfg.configuration import Configurator
+from repoze.tm import after_end
+from repoze.tm import isActive
 
 from tutorial.models import DBSession
 from tutorial.models import initialize_sql
 from tutorial.models import RootFactory
 
-class Cleanup:
-    def __init__(self, cleaner):
-        self.cleaner = cleaner
-    def __del__(self):
-        self.cleaner()
-
 def handle_teardown(event):
     environ = event.request.environ
-    environ['tutorial.sasession'] = Cleanup(DBSession.remove)
+    if isActive(environ):
+        t = transaction.get()
+        after_end.register(DBSession.remove, t)
 
 def app(global_config, **settings):
     """ This function returns a WSGI application.
@@ -22,8 +22,8 @@ def app(global_config, **settings):
     """
     db_string = settings.get('db_string')
     if db_string is None:
-        raise ValueError(
-            "No 'db_string' value in application configuration.")
+        raise ValueError("No 'db_string' value in application "
+                         "configuration.")
     initialize_sql(db_string)
     config = Configurator(settings=settings, root_factory=RootFactory)
     config.begin()
diff --git a/docs/tutorials/bfgwiki2/src/basiclayout/tutorial/run.py b/docs/tutorials/bfgwiki2/src/basiclayout/tutorial/run.py
index bc1197115..6105d3eea 100644
--- a/docs/tutorials/bfgwiki2/src/basiclayout/tutorial/run.py
+++ b/docs/tutorials/bfgwiki2/src/basiclayout/tutorial/run.py
@@ -1,17 +1,17 @@
+import transaction
+
 from repoze.bfg.configuration import Configurator
+from repoze.tm import after_end
+from repoze.tm import isActive
 
 from tutorial.models import DBSession
 from tutorial.models import initialize_sql
 
-class Cleanup:
-    def __init__(self, cleaner):
-        self.cleaner = cleaner
-    def __del__(self):
-        self.cleaner()
-
 def handle_teardown(event):
     environ = event.request.environ
-    environ['tutorial.sasession'] = Cleanup(DBSession.remove)
+    if isActive(environ):
+        t = transaction.get()
+        after_end.register(DBSession.remove, t)
 
 def app(global_config, **settings):
     """ This function returns a WSGI application.
diff --git a/docs/tutorials/bfgwiki2/src/models/tutorial/run.py b/docs/tutorials/bfgwiki2/src/models/tutorial/run.py
index d00d32265..6105d3eea 100644
--- a/docs/tutorials/bfgwiki2/src/models/tutorial/run.py
+++ b/docs/tutorials/bfgwiki2/src/models/tutorial/run.py
@@ -1,17 +1,17 @@
+import transaction
+
 from repoze.bfg.configuration import Configurator
+from repoze.tm import after_end
+from repoze.tm import isActive
 
 from tutorial.models import DBSession
 from tutorial.models import initialize_sql
 
-class Cleanup:
-    def __init__(self, cleaner):
-        self.cleaner = cleaner
-    def __del__(self):
-        self.cleaner()
-
 def handle_teardown(event):
     environ = event.request.environ
-    environ['tutorial.sasession'] = Cleanup(DBSession.remove)
+    if isActive(environ):
+        t = transaction.get()
+        after_end.register(DBSession.remove, t)
 
 def app(global_config, **settings):
     """ This function returns a WSGI application.
@@ -21,7 +21,8 @@ def app(global_config, **settings):
     """
     db_string = settings.get('db_string')
     if db_string is None:
-        raise ValueError("No 'db_string' value in application configuration.")
+        raise ValueError("No 'db_string' value in application "
+                         "configuration.")
     initialize_sql(db_string)
     config = Configurator(settings=settings)
     config.begin()
diff --git a/docs/tutorials/bfgwiki2/src/views/tutorial/run.py b/docs/tutorials/bfgwiki2/src/views/tutorial/run.py
index d00d32265..6105d3eea 100644
--- a/docs/tutorials/bfgwiki2/src/views/tutorial/run.py
+++ b/docs/tutorials/bfgwiki2/src/views/tutorial/run.py
@@ -1,17 +1,17 @@
+import transaction
+
 from repoze.bfg.configuration import Configurator
+from repoze.tm import after_end
+from repoze.tm import isActive
 
 from tutorial.models import DBSession
 from tutorial.models import initialize_sql
 
-class Cleanup:
-    def __init__(self, cleaner):
-        self.cleaner = cleaner
-    def __del__(self):
-        self.cleaner()
-
 def handle_teardown(event):
     environ = event.request.environ
-    environ['tutorial.sasession'] = Cleanup(DBSession.remove)
+    if isActive(environ):
+        t = transaction.get()
+        after_end.register(DBSession.remove, t)
 
 def app(global_config, **settings):
     """ This function returns a WSGI application.
@@ -21,7 +21,8 @@ def app(global_config, **settings):
     """
     db_string = settings.get('db_string')
     if db_string is None:
-        raise ValueError("No 'db_string' value in application configuration.")
+        raise ValueError("No 'db_string' value in application "
+                         "configuration.")
     initialize_sql(db_string)
     config = Configurator(settings=settings)
     config.begin()