Exception handling for database commit operations

ref-test/app/models/dataset.py

@@ -5,6 +5,7 @@ from ..tools.logs import write
 from flask import flash
 from flask import current_app as app
 from flask_login import current_user
+from sqlalchemy.exc import SQLAlchemyError
 from werkzeug.utils import secure_filename
 
 from datetime import datetime
@@ -45,7 +46,12 @@ class Dataset(db.Model):
         for dataset in Dataset.query.all():
             dataset.default = False
         self.default = True
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when setting default dataset {self.id}: {exception}')
+            return False, f'Database error {exception}.'
         write('system.log', f'Dataset {self.id} set as default by {current_user.get_username()}.')
         flash(message='Dataset set as default.', category='success')
         return True, f'Dataset set as default.'
@@ -63,9 +69,14 @@ class Dataset(db.Model):
         filename = secure_filename('.'.join([self.id,'json']))
         data = Path(app.config.get('DATA'))
         file_path = path.join(data, 'questions', filename)
-        remove(file_path)
+        try:
             db.session.delete(self)
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when trying to delete dataset {self.id}: {exception}')
+            return False, f'Database error: {exception}'
+        remove(file_path)
         return True, 'Dataset deleted.'
     
     def create(self, data:list, default:bool=False):
@@ -78,8 +89,13 @@ class Dataset(db.Model):
         self.creator = current_user
         if default: self.make_default()
         write('system.log', f'New dataset {self.get_name()} added by {current_user.get_username()}.')
+        try:
             db.session.add(self)
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when trying to crreate dataset {self.id}: {exception}')
+            return False, f'Database error: {exception}'
         return True, 'Dataset created.'
 
     def check_file(self):
@@ -103,6 +119,11 @@ class Dataset(db.Model):
             dump(data, file, indent=2)
         write('system.log', f'Dataset {self.id} edited by {current_user.get_username()}.')
         flash(f'Dataset {self.get_name()} successfully edited.', 'success')
+        try:
             db.session.add(self)
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when trying to update dataset {self.id}: {exception}')
+            return False, f'Database error: {exception}'
         return True, 'Dataset successfully edited.'

ref-test/app/models/entry.py

@@ -7,6 +7,7 @@ from .test import Test
 from flask_login import current_user
 from flask_mail import Message
 from smtplib import SMTPException
+from sqlalchemy.exc import SQLAlchemyError
 
 from datetime import datetime, timedelta
 from uuid import uuid4
@@ -70,23 +71,32 @@ class Entry(db.Model):
 
     def ready(self):
         self.generate_id()
+        try:
             db.session.add(self)
             db.session.commit()
-        write('tests.log', f'New test ready for {self.get_first_name()} {self.get_surname()}.')
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when preparing new entry for {self.get_surname()}, {self.get_first_name()}: {exception}')
+            return False, f'Database error: {exception}'
+        write('tests.log', f'New test ready for {self.get_surname()}, {self.get_first_name()} with id {self.id}.')
         return True, f'Test ready.'
 
     def start(self):
         self.start_time = datetime.now()
         self.status = 'started'
-        write('tests.log', f'Test started by {self.get_first_name()} {self.get_surname()}.')
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when starting test for {self.get_surname()}, {self.get_first_name()}: {exception}')
+            return False, f'Database error: {exception}'
+        write('tests.log', f'Test started by {self.get_surname()}, {self.get_first_name()} with id {self.id}.')
         return True, f'New test started with id {self.id}.'
 
     def complete(self, answers:dict=None, result:dict=None):
         self.end_time = datetime.now()
         self.answers = answers
         self.result = result
-        write('tests.log', f'Test completed by {self.get_first_name()} {self.get_surname()}.')
         delta = timedelta(minutes=int(0 if self.test.time_limit is None else self.test.time_limit)+1)
         if not self.test.time_limit or self.end_time <= self.start_time + delta:
             self.status = 'completed'
@@ -94,7 +104,13 @@ class Entry(db.Model):
         else:
             self.status = 'late'
             self.valid = False
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when submitting entry for {self.get_surname()}, {self.get_first_name()}: {exception}')
+            return False, f'Database error: {exception}'
+        write('tests.log', f'Test completed by {self.get_surname()}, {self.get_first_name()} with id {self.id}.')
         return True, f'Test entry completed for id {self.id}.'
 
     def validate(self):
@@ -102,15 +118,25 @@ class Entry(db.Model):
         if self.status == 'started': return False, 'The entry is still pending.'
         self.valid = True
         self.status = 'completed'
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when validating entry {self.id}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'The entry {self.id} has been validated by {current_user.get_username()}.')
         return True, f'The entry {self.id} has been validated.'
 
     def delete(self):
         id = self.id
         name = f'{self.get_first_name()} {self.get_surname()}'
+        try:
             db.session.delete(self)
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when deleting entry {id}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'The entry {id} by {name} has been deleted by {current_user.get_username()}.')
         return True, 'Entry deleted.'
     

ref-test/app/models/test.py

@@ -3,6 +3,7 @@ from ..tools.forms import JsonEncodedDict
 from ..tools.logs import write
 
 from flask_login import current_user
+from sqlalchemy.exc import SQLAlchemyError
 
 from datetime import date, datetime
 import secrets
@@ -52,15 +53,25 @@ class Test(db.Model):
             errors.append('The expiry date cannot be before the start date.')
         if errors:
             return False, errors
+        try:
             db.session.add(self)
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when creating test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Test with code {self.get_code()} created by {current_user.get_username()}.')
         return True, f'Test with code {self.get_code()} has been created.'
     
     def delete(self):
         if self.entries: return False, f'Cannot delete a test with submitted entries.'
         db.session.delete(self)
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when deleting test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Test with code {self.get_code()} has been deleted by {current_user.get_username()}.')
         return True, f'Test with code {self.get_code()} has been deleted.'
     
@@ -68,7 +79,12 @@ class Test(db.Model):
         now = datetime.now()
         if self.start_date.date() > now.date():
             self.start_date = now
+            try:
                 db.session.commit()
+            except SQLAlchemyError as exception:
+                db.session.rollback()
+                write('system.log', f'Database error when launching test {self.get_code()}: {exception}')
+                return False, f'Database error: {exception}'
             write('system.log', f'Test with code {self.get_code()} has been started by {current_user.get_username()}.')
             return True,  f'Test with code {self.get_code()} has been started.'
         return False, f'Test with code {self.get_code()} has already started.'
@@ -77,7 +93,12 @@ class Test(db.Model):
         now = datetime.now()
         if self.end_date >= now:
             self.end_date = now
+            try:
                 db.session.commit()
+            except SQLAlchemyError as exception:
+                db.session.rollback()
+                write('system.log', f'Database error when closing test {self.get_code()}: {exception}')
+                return False, f'Database error: {exception}'
             write('system.log', f'Test with code {self.get_code()} ended by {current_user.get_username()}.')
             return True, f'Test with code {self.get_code()} has been ended.'
         return False, f'Test with code {self.get_code()} has already ended.'
@@ -87,7 +108,12 @@ class Test(db.Model):
         code = secrets.token_hex(3).lower()
         adjustments[code] = time
         self.adjustments = adjustments
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when adding adjustment to test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Time adjustment for {time} minutes with code {code} added to test {self.get_code()} by {current_user.get_username()}.')
         return True, f'Time adjustment for {time} minutes added to test {self.get_code()}. This can be accessed using the user code {code.upper()}.'
 
@@ -95,7 +121,12 @@ class Test(db.Model):
         if not self.adjustments: return False, f'There are no adjustments configured for test {self.get_code()}.'
         self.adjustments.pop(code)
         if not self.adjustments: self.adjustments = None
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when deleting adjustment from test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Time adjustment for with code {code} has been removed from test {self.get_code()} by {current_user.get_username()}.')
         return True, f'Time adjustment for with code {code} has been removed from test {self.get_code()}.'
 
@@ -104,6 +135,11 @@ class Test(db.Model):
         if start_date: self.start_date = start_date
         if end_date: self.end_date = end_date
         if time_limit is not None: self.time_limit = time_limit
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when updating test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Test with code {self.get_code()} has been updated by user {current_user.get_username()}.')
         return True, f'Test with code {self.get_code()} has been updated by.'

ref-test/app/models/user.py

@@ -7,6 +7,7 @@ from flask.helpers import url_for
 from flask_login import current_user, login_user, logout_user, UserMixin
 from flask_mail import Message
 from smtplib import SMTPException
+from sqlalchemy.exc import SQLAlchemyError
 from werkzeug.security import check_password_hash, generate_password_hash
 
 import secrets
@@ -61,8 +62,13 @@ class User(UserMixin, db.Model):
             if user.get_username() == self.get_username(): return False, f'Username {self.get_username()} already in use.'
             if user.get_email() == self.get_email(): return False, f'Email address {self.get_email()} already in use.'
         self.set_password(password=password)
+        try:
             db.session.add(self)
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when registering user {self.get_username()}: {exception}')
+            return False, f'Database error: {exception}'
         write('users.log', f'User \'{self.get_username()}\' was created with id \'{self.id}\'.')
         if notify:
             email = Message(
@@ -149,19 +155,35 @@ class User(UserMixin, db.Model):
             mail.send(email)
         except SMTPException as exception:
             write('system.log', f'SMTP Error while trying to reset password for {self.get_username()} with error: {exception}')
+            db.session.rollback()
             return jsonify({'error': f'SMTP Error: {exception}'}), 500
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when resetting password for user {self.get_username()}: {exception}')
+            return False, f'Database error: {exception}'
         return jsonify({'success': 'Your password reset link has been generated.'}), 200
 
     def clear_reset_tokens(self):
         self.reset_token = self.verification_token = None
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when resetting clearing reset tokens for user {self.get_username()}: {exception}')
+            return False, f'Database error: {exception}'
     
     def delete(self, notify:bool=False):
         username = self.get_username()
         email_address = self.get_email()
+        try:
             db.session.delete(self)
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when deleting user {self.get_username()}: {exception}')
+            return False, f'Database error: {exception}'
         message = f'User \'{username}\' was deleted by \'{current_user.get_username()}\'.'
         write('users.log', message)
         if notify:
@@ -200,7 +222,12 @@ class User(UserMixin, db.Model):
             for entry in User.query.all():
                 if entry.get_email() == email and not entry == self: return False, f'The email address {email} is already in use.'
             self.set_email(email)
+        try:
             db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when updating user {self.get_username()}: {exception}')
+            return False, f'Database error: {exception}'
         _current_user = current_user.get_username() if current_user.is_authenticated else 'anonymous'
         write('system.log', f'Information for user {self.get_username()} has been updated by {_current_user}.')
         if notify: