This approach uses part of sqlalchemy example history_meta code

adapted to recording inserts and updates.

This removes need to manually create history tables.

Our code still remains in control of when history records are
created.

app/dao/dao_utils.py

@@ -0,0 +1,48 @@
+import datetime
+
+from functools import wraps
+
+
+def create_history(obj):
+    history_mapper = obj.__history_mapper__
+    history_model = history_mapper.class_
+    history = history_model()
+    if obj.version:
+        obj.version += 1
+    else:
+        obj.version = 1
+        obj.created_at = datetime.datetime.now()
+    for prop in history_mapper.iterate_properties:
+        if obj.__mapper__.get_property(prop.key):
+            setattr(history, prop.key, getattr(obj, prop.key))
+    history.created_by_id = obj.created_by.id
+    return history
+
+
+def transactional(func):
+    @wraps(func)
+    def commit_or_rollback(*args, **kwargs):
+        from flask import current_app
+        from app import db
+        try:
+            func(*args, **kwargs)
+            db.session.commit()
+        except Exception as e:
+            current_app.logger.error(e)
+            db.session.rollback()
+            raise
+    return commit_or_rollback
+
+
+def versioned(func):
+    @wraps(func)
+    def record_version(*args, **kwargs):
+        import itertools
+        from app import db
+        from app.history_meta import versioned_objects
+        from app.dao.dao_utils import create_history
+        func(*args, **kwargs)
+        for obj in versioned_objects(itertools.chain(db.session.new, db.session.dirty)):
+            history = create_history(obj)
+            db.session.add(history)
+    return record_version

app/dao/notifications_dao.py

@@ -30,22 +30,7 @@ from app.clients import (
     STATISTICS_REQUESTED
 )
 
-from functools import wraps
-
-
-def transactional(func):
-    @wraps(func)
-    def commit_or_rollback(*args, **kwargs):
-        from flask import current_app
-        from app import db
-        try:
-            func(*args, **kwargs)
-            db.session.commit()
-        except Exception as e:
-            current_app.logger.error(e)
-            db.session.rollback()
-            raise
-    return commit_or_rollback
+from app.dao.dao_utils import transactional
 
 
 def get_character_count_of_content(content, encoding='utf-8'):

app/dao/services_dao.py

@@ -1,7 +1,14 @@
+import uuid
+
 from app import db
 from app.models import Service
 from sqlalchemy import asc
 
+from app.dao.dao_utils import (
+    transactional,
+    versioned
+)
+
 
 def dao_fetch_all_services():
     return Service.query.order_by(asc(Service.created_at)).all()
@@ -19,22 +26,20 @@ def dao_fetch_service_by_id_and_user(service_id, user_id):
     return Service.query.filter(Service.users.any(id=user_id)).filter_by(id=service_id).one()
 
 
+@transactional
+@versioned
 def dao_create_service(service, user):
-    try:
-        from app.dao.permissions_dao import permission_dao
-        service.users.append(user)
-        permission_dao.add_default_service_permissions_for_user(user, service)
-        db.session.add(service)
-    except Exception as e:
-        db.session.rollback()
-        raise e
-    else:
-        db.session.commit()
+    from app.dao.permissions_dao import permission_dao
+    service.users.append(user)
+    permission_dao.add_default_service_permissions_for_user(user, service)
+    service.id = uuid.uuid4()  # must be set now so version history model can use same id
+    db.session.add(service)
 
 
+@transactional
+@versioned
 def dao_update_service(service):
     db.session.add(service)
-    db.session.commit()
 
 
 def dao_add_user_to_service(service, user, permissions=[]):