From 8b3ca76b980f126912de1bc8ffa067c199693eb3 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Micha=C5=82=20Dulko?= Date: Thu, 31 Dec 2015 14:34:30 +0100 Subject: [PATCH] Fix race conditions in migration 061 Migration 061 is supposed to add new `data_timestamp` field and populate it with value of `created_at` column. This was done by selecting all the backups and doing updates one-by-one. As it wasn't done in transaction solution was prone to race condition when a new backup is added while running the migration. This means that this migration could cause problems when running in live environment. With blueprint online-schema-upgrades we want to make Cinder able to perform migrations live. A solution is to change this statement to a single DB query which updates all the rows. This commit also removes unnecessary update to snapshot_id added there. As this column is nullable it will by default be NULL, so there's no need to set it manually to that value. As before and after this commit the migration does logically the same, this should be safe even if someone is doing inter-release deployments. An alternative would be to simply add transaction to the update step in the migration, but that would effectively lock the table for longer period of time than atomic one-query update. Closes-Bug: 1530358 Change-Id: Ib8733c096a3dbe2bad00beaf5734936ffcddda33 --- .../061_add_snapshot_id_timestamp_to_backups.py | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-) diff --git a/cinder/db/sqlalchemy/migrate_repo/versions/061_add_snapshot_id_timestamp_to_backups.py b/cinder/db/sqlalchemy/migrate_repo/versions/061_add_snapshot_id_timestamp_to_backups.py index 5b242d7ac..054cef341 100644 --- a/cinder/db/sqlalchemy/migrate_repo/versions/061_add_snapshot_id_timestamp_to_backups.py +++ b/cinder/db/sqlalchemy/migrate_repo/versions/061_add_snapshot_id_timestamp_to_backups.py @@ -25,16 +25,6 @@ def upgrade(migrate_engine): data_timestamp = Column('data_timestamp', DateTime) backups.create_column(snapshot_id) - backups.update().values(snapshot_id=None).execute() backups.create_column(data_timestamp) - backups.update().values(data_timestamp=None).execute() - - # Copy existing created_at timestamp to data_timestamp - # in the backups table. - backups_list = list(backups.select().execute()) - for backup in backups_list: - backup_id = backup.id - backups.update().\ - where(backups.c.id == backup_id).\ - values(data_timestamp=backup.created_at).execute() + backups.update().values(data_timestamp=backups.c.created_at).execute() -- 2.45.2