juju bootstrap older version: ERROR requested agent version major.minor mismatch

This is unviable without making significant changes to the way bootstrap works. The client code currently knows how to create the bootstrap instance, and works in concert with the exact same agent version on it.

We would need to either introduce cross-version compatibility between client/server bootstrap procedures (which I think would be too costly in terms of maintenance, and therefore a mistake); or we could split the client-side bootstrap code into a separate binary, and have the client fetch the appropriate version from streams.canonical.com. I think the latter would be very reasonable, and probably better than what we have today.

Marking this as Wishlist for now, since it's an improvement over an existing solution.

are you aware of any change in the boostrap procedure between 2.0 and 2.2?, I'm not implying there is not, I'm just not familiar with what the client does to bootstrap the controller and how often this changes.

For historical reasons, your local client can only bootstrap controller with the same major.minor versions.
In other words, 2.0 client can only bootstrap controllers using 2.0.x agents; 2.1 client can only bootstrap 2.1.x agents, etc.

I have updated the error message at bootstrap to be more explicit: https://github.com/juju/juju/pull/7911.

However, we have no intention of changing this behavior in the future. We want to avoid pitfalls where bootstrap may become incompatible between Juju versions.

I have created a separate Wishlist item to deal with splitting of client-side bootstrap, bug # 1721443.

On Thu, Oct 05, 2017 at 04:53:38AM -0000, Anastasia wrote:
> For historical reasons, your local client can only bootstrap controller with the same major.minor versions.
> In other words, 2.0 client can only bootstrap controllers using 2.0.x agents; 2.1 client can only bootstrap 2.1.x agents, etc.
>
> I have updated the error message at bootstrap to be more explicit:
> https://github.com/juju/juju/pull/7911.
>
> However, we have no intention of changing this behavior in the future.
> We want to avoid pitfalls where bootstrap may become incompatible
> between Juju versions.

I understand this reasoning, but we need a method to bootstrap old versions when using snaps, currently with deb packages I keep around in different PPAs each release (2.0, 2.1, etc). If juju could keep a track for each major.minor would be great.

The only method we will have is to compile locally the version needed.