openstack
/
nova
Code Issues Proposed changes

Merge "[stable-only] Use a separate transaction for reading after race" into stable/queens

This commit is contained in:
Zuul 2020-11-03 11:16:24 +00:00 committed by Gerrit Code Review
parent 39afe4c7c7 d696a636bb
commit 1516fdd394
2 changed files with 14 additions and 5 deletions
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8
nova/objects/resource_provider.py
View File

@ -1911,7 +1911,13 @@ def _ensure_lookup_table_entry(ctx, tbl, external_id):
except db_exc.DBDuplicateEntry:
# Another thread added it just before us, so just read the
# internal ID that that thread created...
res = ctx.session.execute(sel).fetchall()
# NOTE(melwitt): We need to use a separate transaction to read
# back the external_id written by another thread. REPEATABLE_READ
# is the default isolation level for InnoDB, so reads from within
# the same transaction will be consistent in such a case.
# https://dev.mysql.com/doc/refman/8.0/en/innodb-transaction-isolation-levels.html
with db_api.api_context_manager.reader.independent.using(ctx):
res = ctx.session.execute(sel).fetchall()
return res[0][0]

11
nova/tests/functional/db/test_resource_provider.py
View File

@ -19,10 +19,12 @@ from oslo_config import cfg
from oslo_db import exception as db_exc
from oslo_db.sqlalchemy import enginefacade
from oslo_db.sqlalchemy import test_base
from oslo_db.sqlalchemy import test_fixtures as db_fixtures
import sqlalchemy as sa
import nova
from nova import context
from nova.db.sqlalchemy import api as db_api
from nova.db.sqlalchemy import api_models
from nova.db.sqlalchemy import migration as sa_migration
from nova import exception
@ -3044,6 +3046,10 @@ class TestTransactionIsolation(test_base.MySQLOpportunisticTestCase):
# to read/write to our test MySQL database.
self.test_context_manager = enginefacade.transaction_context()
self.test_context_manager.patch_factory(self.enginefacade)
# We need to patch our global API database transaction context manager
# in order to have it read/write to our test MySQL database too.
self.useFixture(db_fixtures.ReplaceEngineFacadeFixture(
db_api.api_context_manager, self.test_context_manager))
self.ctx = context.RequestContext('fake-user', 'fake-project')
@ -3077,9 +3083,6 @@ class TestTransactionIsolation(test_base.MySQLOpportunisticTestCase):
# Now run the lookup table method to test the behavior of the scenario.
with self.test_context_manager.writer.using(self.ctx):
# FIXME(melwitt): Because of the bug, we expect IndexError to be
# raised when we call _ensure_lookup_table_entry.
self.assertRaises(
IndexError, rp_obj._ensure_lookup_table_entry,
rp_obj._ensure_lookup_table_entry(
self.ctx, api_models.Project.__table__,
uuidsentinel.external_id)