I believe @AnujGupta's answer is correct. However the rollback can itself raise an exception which you should catch and handle:
from django.db import transaction, DatabaseError
try:
a.save()
except DatabaseError:
try:
transaction.rollback()
except transaction.TransactionManagementError:
# Log or handle otherwise
If you find you're rewriting this code in various save() locations, you can extract-method:
import traceback
def try_rolling_back():
try:
transaction.rollback()
log.warning('rolled back') # example handling
except transaction.TransactionManagementError:
log.exception(traceback.format_exc()) # example handling
Finally, you can prettify it using a decorator that protects methods which use save():
from functools import wraps
def try_rolling_back_on_exception(fn):
@wraps(fn)
def wrapped(*args, **kwargs):
try:
return fn(*args, **kwargs)
except:
traceback.print_exc()
try_rolling_back()
return wrapped
@try_rolling_back_on_exception
def some_saving_method():
# ...
model.save()
# ...
Even if you implement the decorator above, it's still convenient to keep try_rolling_back() as an extracted method in case you need to use it manually for cases where specific handling is required, and the generic decorator handling isn't enough.