barbican/barbican/common/resources.py
Dave McCowan 71829664b2 Fix Race Condition in get_or_create_project()
get_or_create_project() first calls a get (query of the database).
If that fails, then it calls create.  The issues is when
there are two threads and both fail the original get, then
each will call create.  One of those creates will fail, resulting
in the traceback.

One way to protect this critical region is to call create first,
then if that fails, call get.

In this case, get_or_create_project() is called for every
Barbican API operation.  The create action (which is slow), happens
once per project for the life of the cloud.  The get action happens
every other time.  For performance gains, I left call get first,
since that call succeeds almost always.

Change-Id: I2f13b495a6b45e226e0742291f76ee88dbcf52df
Closes-bug: #1726203
2017-10-22 22:19:26 -04:00

59 lines
1.9 KiB
Python

# Copyright (c) 2013-2014 Rackspace, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Shared business logic.
"""
from barbican.common import exception
from barbican.common import utils
from barbican.model import models
from barbican.model import repositories
LOG = utils.getLogger(__name__)
GLOBAL_PREFERRED_PROJECT_ID = "GLOBAL_PREFERRED"
def get_or_create_global_preferred_project():
return get_or_create_project(GLOBAL_PREFERRED_PROJECT_ID)
def get_or_create_project(project_id):
"""Returns project with matching project_id.
Creates it if it does not exist.
:param project_id: The external-to-Barbican ID for this project.
:param project_repo: Project repository.
:return: Project model instance
"""
project_repo = repositories.get_project_repository()
project = project_repo.find_by_external_project_id(project_id,
suppress_exception=True)
if not project:
LOG.debug('Creating project for %s', project_id)
project = models.Project()
project.external_id = project_id
project.status = models.States.ACTIVE
try:
project_repo.create_from(project)
except exception.ConstraintCheck:
# catch race condition for when another thread just created one
project = project_repo.find_by_external_project_id(
project_id,
suppress_exception=False)
return project