def test_successful_read_only_exit_commits_or_aborts_implicitly(self):
# When a read-only policy exits normally, there is no need to
# complete the transaction. It aborts or commits implicitly.
# (The choice is up to the implementation; the point of
# read-only is that you can't tell the difference.)
with DatabaseTransactionPolicy(read_only=True):
self.readFromDatabase()
# No transaction ongoing at this point.
check_no_transaction()
def test_successful_read_only_exit_commits_or_aborts_implicitly(self):
# When a read-only policy exits normally, there is no need to
# complete the transaction. It aborts or commits implicitly.
# (The choice is up to the implementation; the point of
# read-only is that you can't tell the difference.)
with DatabaseTransactionPolicy(read_only=True):
self.readFromDatabase()
# No transaction ongoing at this point.
check_no_transaction()
def test_check_no_transaction(self):
# check_no_transaction() should be a no-op when there are no
# transactions in operation.
transaction.abort()
isolation.check_no_transaction()
# check_no_transaction() raises TransactionInProgress when a
# transaction has begun.
self.createTransaction()
self.assertRaises(isolation.TransactionInProgress,
isolation.check_no_transaction)
def test_check_no_transaction(self):
# check_no_transaction() should be a no-op when there are no
# transactions in operation.
transaction.abort()
isolation.check_no_transaction()
# check_no_transaction() raises TransactionInProgress when a
# transaction has begun.
self.createTransaction()
self.assertRaises(
isolation.TransactionInProgress,
isolation.check_no_transaction)
def test_aborts_on_failure(self):
# If the context handler exits with an exception, it aborts the
# transaction.
class CompleteFailure(Exception):
pass
try:
with DatabaseTransactionPolicy(read_only=False):
test_token = self.writeToDatabase()
raise CompleteFailure()
except CompleteFailure:
pass
# No transaction ongoing at this point.
check_no_transaction()
# The change has rolled back.
self.assertFalse(self.hasDatabaseBeenWrittenTo(test_token))
def test_aborts_on_failure(self):
# If the context handler exits with an exception, it aborts the
# transaction.
class CompleteFailure(Exception):
pass
try:
with DatabaseTransactionPolicy(read_only=False):
test_token = self.writeToDatabase()
raise CompleteFailure()
except CompleteFailure:
pass
# No transaction ongoing at this point.
check_no_transaction()
# The change has rolled back.
self.assertFalse(self.hasDatabaseBeenWrittenTo(test_token))
def transaction(self):
"""Context manager to ring-fence database activity.
Ensures that no transaction is in progress on entry, and
commits on a successful exit. Exceptions are propagated once
the transaction has been aborted.
This intentionally cannot be nested. Keep it simple.
"""
check_no_transaction()
try:
yield self._transaction_manager
except:
self._transaction_manager.abort()
# Let the exception propagate.
raise
else:
self._transaction_manager.commit()
def transaction(self):
"""Context manager to ring-fence database activity.
Ensures that no transaction is in progress on entry, and
commits on a successful exit. Exceptions are propagated once
the transaction has been aborted.
This intentionally cannot be nested. Keep it simple.
"""
check_no_transaction()
try:
yield self._transaction_manager
except:
self._transaction_manager.abort()
# Let the exception propagate.
raise
else:
self._transaction_manager.commit()
def test_can_be_empty(self):
# An empty transaction policy works fine.
with DatabaseTransactionPolicy():
pass
# You still end up with a clean slate, transaction-wise.
check_no_transaction()
def test_can_be_empty(self):
# An empty transaction policy works fine.
with DatabaseTransactionPolicy():
pass
# You still end up with a clean slate, transaction-wise.
check_no_transaction()
