Log a warning if a Pyramid request ends with uncommitted DB session c…

…hanges

The previous `session.dirty` check only tested for _changes_ to existing
DB objects which have not been flushed. It did not check for added or
deleted model objects which had not yet been flushed to the DB, or for
changes which have been flushed inside a transaction but not yet _committed_.

When debugging #4704 we want to
specifically catch additions (of annotations) to the DB which have been
flushed (by `storage.create_annotation`) but not yet committed.

h/db/__init__.py

@@ -21,6 +21,8 @@
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm import sessionmaker
 
+from h.util.session_tracker import Tracker
+
 __all__ = (
     'Base',
     'Session',
@@ -82,6 +84,10 @@ def _session(request):
     else:
         zope.sqlalchemy.register(session, transaction_manager=tm)
 
+    # Track uncommitted changes so we can verify that everything was either
+    # committed or rolled back when the request finishes.
+    tracker = Tracker(session)
+
     # pyramid_tm doesn't always close the database session for us.
     #
     # For example if an exception view accesses the session and causes a new
@@ -96,10 +102,13 @@ def _session(request):
     # See: https://github.com/Pylons/pyramid_tm/issues/40
     @request.add_finished_callback
     def close_the_sqlalchemy_session(request):
-        if session.dirty:
-            request.sentry.captureMessage('closing a dirty session', stack=True, extra={
-                'dirty': session.dirty,
+        changes = tracker.uncommitted_changes()
+        if changes:
+            msg = 'closing a session with uncommitted changes'
+            request.sentry.captureMessage(msg, stack=True, extra={
+                'changes': changes,
             })
+            log.warn('{} {}'.format(msg, changes))
         session.close()
 
     return session