Sounds like Heroku could make this available for apps that don't use a
[SQL?] DB.

On Aug 30, 11:13 pm, Peter van Hardenberg <[email protected]> wrote:
> This totally sucks. I see no reason we can't write software which can help
> take care of this and provide superior versioning in the system. Ultimately
> the lesson here is that all cloud services need to be capable of being in
> intermediate states (or reverting part way through!) during all deploys.
> This is something that is easy to ignore on a new or smaller app, but
> becomes increasingly clear as your dataset grows into the hundreds of gigs.
>
> Surely there is a careful thinker among us who can put their brain to work
> on what is really an essential problem: how to make database schemas and
> ORMs cooperate with version control/software releases?
>
> -pvh
>
>
>
>
>
>
>
> On Tue, Aug 30, 2011 at 9:10 PM, Tom O'Neill <[email protected]> wrote:
> > 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 <[email protected]> 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_do...
>
> > > 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 <[email protected]>
> > 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.
>
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