In a sufficiently large/complex environment db and code changes necessarily happen at different times, even if you try to make them happen together. So one of the changes (code or db) needs to be backwards compatible each release - push the backwards compatible change first and then the other. Turns deployment into a 2-step process, but it's easy enough on the Heroku stack.
On Tue, Aug 30, 2011 at 6:42 PM, Pedro Belo <pe...@heroku.com> wrote: > Hey guys, > > We have a lot of interest on this subject at Heroku, if anything > because we use the product every time we can and we understand that > having to put the app on maintenance mode every time you deploy a > migration is not acceptable. > > That said, the problem with migrations like Mike said goes a bit > further - a big part of it is that most migrations are just not safe > to be executed against a live system, and on that front I don't > believe there's a lot we can do. You just need to carefully design > your migrations and change your deploy process to accomodate them - > something I tried to convey on this blog post: > > http://pedro.herokuapp.com/past/2011/7/13/rails_migrations_with_no_downtime/ > > If you're designing your migrations with hot compatibility in mind, > the workflow imposed by Heroku should work - although it definitely > comes with effort. > > Well, let me know if you have any feedback on this topic, I'd love to hear it. > > Thanks, > Pedro > > On Tue, Aug 30, 2011 at 4:53 PM, Mike Abner <mike.ab...@gmail.com> wrote: >> We're thinking about having a migrations branch where we put all migrations. >> They get merged to master first, then pushed and run, and then after those >> complete we merge the new code to master and push again. >> It does mean that you have to spend more time and effort dealing with data >> model changes and not making breaking changes in the data model. For >> instance, if you want to change a column name you have to have a migration >> that creates a new column and moves all the data over and then after you >> push your new code you have to write a migration to remove the old >> column/data. It's more work and takes more planning/discipline, but I don't >> think it's that big of an issue given the ease of just about everything else >> on the heroku platform. >> Mike >> >> On Tuesday, August 30, 2011 at 4:34 PM, Jonathan Owens wrote: >> >> That only half solves it by forcing downtime you'd be taking anyway because >> your app is likely to crash if started before the migrations run, as you are >> forced to do. Having to take downtime just to add a field is pretty lame. >> We're looking at running our migrations from an EC2 server since we use RDS. >> Heroku-hosted postgres could make that more tricky. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Heroku" group. >> To view this discussion on the web visit >> https://groups.google.com/d/msg/heroku/-/IsBLMKs4c0sJ. >> To post to this group, send email to heroku@googlegroups.com. >> To unsubscribe from this group, send email to >> heroku+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/heroku?hl=en. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Heroku" group. >> To post to this group, send email to heroku@googlegroups.com. >> To unsubscribe from this group, send email to >> heroku+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/heroku?hl=en. >> > > -- > You received this message because you are subscribed to the Google Groups > "Heroku" group. > To post to this group, send email to heroku@googlegroups.com. > To unsubscribe from this group, send email to > heroku+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/heroku?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Heroku" group. To post to this group, send email to heroku@googlegroups.com. To unsubscribe from this group, send email to heroku+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/heroku?hl=en.
