Re: [openstack-dev] [Nova] question about DB migration difficulty
Michael Still wrote on 11/13/2013 04:27:17 PM: > ... > This was actually discussed in the session as an example of how other > projects handle these problems. Our concerns (IIRC) were that it would > take even more patches to land, and each of those patches is quite > hard to land in nova these days. More patches than what? I thought the concern was that there is no solution, not a competition between two solutions. Is there some simpler solution to the delete column case in which each migration can be undone after being partially applied? > Additionally, it increases the > complexity of our code a lot, because we have to handle databases in > all possible states because of how our continuous deployment model > works. I'm not sure I understand this. The approach I cited has code that always works, and each rev of the code needs to co-exist with only the previous rev and the following rev. Thanks, Mike ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [Nova] question about DB migration difficulty
On Thu, Nov 14, 2013 at 5:18 AM, Mike Spreitzer wrote: > This is a follow-up to the design summit discussion about DB migrations. > There was concern about the undo-ability of some migrations. The specific > example cited was removal of a column. Could that be done with the > following three migrations, each undo-able? First, change the code to keep > writing the column but no longer read the column. Second migration changes > the code to neither read nor write the column. Third migration physically > removes the column. This was actually discussed in the session as an example of how other projects handle these problems. Our concerns (IIRC) were that it would take even more patches to land, and each of those patches is quite hard to land in nova these days. Additionally, it increases the complexity of our code a lot, because we have to handle databases in all possible states because of how our continuous deployment model works. Objects bring us closer to being able to do this, but we need objects finished first. Michael -- Rackspace Australia ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
[openstack-dev] [Nova] question about DB migration difficulty
This is a follow-up to the design summit discussion about DB migrations. There was concern about the undo-ability of some migrations. The specific example cited was removal of a column. Could that be done with the following three migrations, each undo-able? First, change the code to keep writing the column but no longer read the column. Second migration changes the code to neither read nor write the column. Third migration physically removes the column.___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
