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Retry update_user when sqlalchemy raises StaleDataErrors

Keystone's update_user() method in the SQL driver processes a lot of
information about how to update users. This includes evaluating password
logic and authentication attempts for PSI-DSS. This logic is evaluated
after keystone pulls the user record from SQL and before it exits the
context manager, which performs the write.

When multiple clients are all updating the same user reference, it's
more likely they will see an HTTP 500 because of race conditions exiting
the context manager. The HTTP 500 is due to stale data when updating
password expiration for old passwords, which happens when setting a new
password for a user.

This commit attempts to handle that case more gracefully than throwing a
500 by detecting StaleDataErrors from sqlalchemy and retrying.  The
identity sql backend will retry the request for clients that have
stale data change from underneath them.

Change-Id: I75590c20e90170ed862f46f0de7d61c7810b5c90
Closes-Bug: 1885753
(cherry picked from commit ceae3566e83b26fd6a1679154eae9b0cef29da64)
changes/35/783735/1 19.0.0
Lance Bragstad 10 months ago
3 changed files with 52 additions and 0 deletions
  1. +8
  2. +38
  3. +6

+ 8
- 0
keystone/identity/backends/ View File

@ -32,6 +32,10 @@ from keystone.identity.backends import sql_model as model
CONF = keystone.conf.CONF
def _stale_data_exception_checker(exc):
return isinstance(exc, sqlalchemy.orm.exc.StaleDataError)
class Identity(base.IdentityDriverBase):
# NOTE(henry-nash): Override the __init__() method so as to take a
# config parameter to enable sql to be used as a domain-specific driver.
@ -208,6 +212,10 @@ class Identity(base.IdentityDriverBase):
return base.filter_user(user_ref.to_dict())
# Explicitly retry on StaleDataErrors, which can happen if two clients
# update the same user's password and the second client has stale password
# information.
def update_user(self, user_id, user):
with sql.session_for_write() as session:
user_ref = self._get_user(session, user_id)

+ 38
- 0
keystone/tests/unit/ View File

@ -16,9 +16,11 @@ import datetime
from unittest import mock
import uuid
import fixtures
import freezegun
from oslo_db import exception as db_exception
from oslo_db import options
from oslo_log import log
import sqlalchemy
from sqlalchemy import exc
from testtools import matchers
@ -983,6 +985,42 @@ class SqlIdentity(SqlTests,
def test_update_user_with_stale_data_forces_retry(self):
# Capture log output so we know oslo.db attempted a retry
log_fixture = self.useFixture(fixtures.FakeLogger(level=log.DEBUG))
# Create a new user
user_dict = unit.new_user_ref(
new_user_dict = PROVIDERS.identity_api.create_user(user_dict)
side_effects = [
# Raise a StaleDataError simulating that another client has
# updated the user's password while this client's request was
# being processed
# The oslo.db library will retry the request, so the second
# time this method is called let's return a valid session
# object
with mock.patch('keystone.common.sql.session_for_write') as m:
m.side_effect = side_effects
# Update a user's attribute, the first attempt will fail but
# oslo.db will handle the exception and retry, the second attempt
# will succeed
new_user_dict['email'] = uuid.uuid4().hex
new_user_dict['id'], new_user_dict)
# Make sure oslo.db retried the update by checking the log output
expected_log_message = (
'Performing DB retry for function keystone.identity.backends.'
self.assertIn(expected_log_message, log_fixture.output)
class SqlTrust(SqlTests, trust_tests.TrustTests):

+ 6
- 0
releasenotes/notes/bug-1885753-51df25f3ff1d9ae8.yaml View File

@ -0,0 +1,6 @@
- |
[`bug 1885753 <>`_]
Keystone's SQL identity backend now retries update user requests to safely
handle stale data when two clients update a user at the same time.