previously valid amazon environment now invalid?

[roger peppe]

On 28 April 2015 at 19:32, Aaron Bentley <aaron.bentley at canonical.com> wrote:
> On 2015-04-28 11:42 AM, roger peppe wrote:
>> The .jenv code was introduced prior to 1.16. How far back in time
>> do we need to preserve compatibility? (genuine question)
>
> We need to support every mode of operation that 1.18 supported.  Juju
> has a special exemption that allows minor releases, rather than
> micro/bugfix releases, to added to Ubuntu.  But in order to use that
> exemption, new versions of Juju are supposed to be equivalent to a
> micro/bugfix release in terms of their compatibility.

So in general version 1.n will need to support every
mode of operation that version 1.n-1 supports? By induction
doesn't that mean we can never remove any features at
all ever from Juju, because every version will need
to support every mode of operation supported by
*all* previous versions?

I'd prefer to think that we can decide on a path forward,
create migration tools if necessary, and eliminate old,
confusing and velocity-impairing cruft from the code
when possible. But I freely admit that I'm code-biased
in this view :)

> We had our own IS people upgrade to juju 1.20 from 1.18 and find that
> juju no longer worked.  That's terrible.

Would it have been so terrible if the release notes had said "to upgrade
to juju 1.20, run this tool to transition your existing local environment
store first"?

  cheers,
    rog.