[Cuis] Updating existing packages

[Juan Vuletich]

On 27/02/2014 10:03 p.m., Ken Dickey wrote:
> On Wed, 26 Feb 2014 21:57:15 -0600
> David Graham<dgraham at unthinkable.org>  wrote:
>
>> I was trying to update one of my working images with the updated
>> SignalProcessing package, but can't seem to figure out how to do it?  I
>> tried using the File List app and and Feature>require:, but neither
>> update the package.
> The package requirement system is designed to load packages in a fresh image.
>
> We do not yet have a package migration/update system.  An update system takes the current and (presumably) new package versions, preflights changes to maintain invariants, then updates all live instances as well as updating code.
>
> The upshot is that at this time, required packages are loaded exactly once.
>
> We hope to keep things simple as long as possible.
>
> -KenD

Thanks David for raising the issue, and Ken for your answer.

Well, making Feature>>require: and FileList [Install] basically work 
seems reasonable to me. I'm pretty sure that the deletion of stuff not 
present in the newer version is handled correctly. Let me take a look. 
Will report back after taking some time to experiment with all this.

In any case, as Ken says, migrating existing instances is a real 
problem. I don't think we can do a general, robust mechanism for this. 
Maybe we could make a package say "I can handle update / deletion / 
whatever is appropriate for existing instances, so new versions of 
myself can be loaded safely". Then, it would be a responsibility of each 
package to handle it. Thoughts?

Cheers,
Juan Vuletich