Proposal: how to make incompatible changes - versioning

[Joseph Reynolds]

On 4/23/20 7:11 AM, Alexander Amelkin wrote:
> 15.04.2020 02:00, Joseph Reynolds пишет:
>> Proposal: how to make incompatible changes
>>
>> This is a proposal to add guidelines for making incompatible changes 
>> to OpenBMC interfaces.  Is it okay to make incompatible changes? Yes, 
>> IMHO: the project will continuously break compatibility in various 
>> ways, and its users will adapt.  The main idea is to minimize churn 
>> and make it easier for users to adapt.
>>
>> As the OpenBMC project moves forward with new releases, it will make 
>> changes that necessarily break existing use cases.  My 
>> recommendations are:
>> - Try hard to maintain forward compatibility.  For example, maintain 
>> all of the BMC's intended user interfaces.
>> - Identify changes that break compatibility.  Briefly describe the 
>> use case, what breaks, how a user can adapt, and cross-link technical 
>> discussions (Gerrit reviews, issues, emails).
>> - Work with maintainers to determine which incompatible changes get 
>> merged and what documentation is needed.
>> - Give users time to adapt to incompatible changes.  For example, 
>> deprecate interfaces in a previous release.
>> - List incompatible changes in the [release notes][] so community 
>> members will know they have to adapt, and link to how to adapt.
>>
>>
> I'd say that any incompatible change must be reflected in the 
> interface version.
>
> As far as I understand, RedFish has all the interfaces strictly 
> specified and those specifications are bound to a specific RedFish 
> version that is then encoded in the URL (e.g. /redfish/v1/).
>
> Any other interface should have a similar approach. A more relaxed 
> one, if we keep our own flavor of REST, could be that each interface 
> could have a Version property (probably also encoded in the REST URL).
>
> That way, any user trying to access an old interface (thus via a 
> non-existant URL) would get a 404.
>
> Internally, for inter-process dbus communication the interface version 
> could be checked during compile time to prevent problems that couldn't 
> be detected by compiler/linker automatically. Those problems are, for 
> instance, incompatible change in the meaning of the values of a property.

Agreed.  The question to ponder: What is our REST API versioning 
strategy?  What  best practices do we follow?
- Joseph

> Alexander.
>