Open Stack

On 09/01/2016 11:52 AM, Dan Smith wrote:
>
> The indirection service is really unrelated to this discussion, IMHO. If
> you take RPC out of the picture, all you have left is a
> direct-to-the-database facade to handle the fact that schema has
> expanded underneath you. As Clint (et al) have said -- designing the
> application to expect schema expansion (and avoiding unnecessary
> contraction) is the key here.

pretty much.  there's no fixed pattern in how to do these.  Every 
version of a data access API will be weighed down with baggage from the 
previous version and an inability to take full advantage of new 
improvements until the next release, and background migrations are 
complicated by the old application undoing their work.  Even small 
migrations mean all these issues have to be considered each time on a 
case-by-case basis.   These are the problems people are hoping to 
improve upon if possible.   The spec at 
https://review.openstack.org/#/c/331740/ is discussing these issues in 
detail and is the first such specification I've seen that tries to get 
into it at this level.