[Breaking change] Release 0.14 is out with some changes to the request and UDF API

[peiwenhu]

Hi,

We have just released version 0.14. This release introduced breaking changes to the request processing API, which includes changes to the RPC (remote procedure call) schema and the UDF (User defined functions) signature.

If you do not use UDF and you don't directly use the RPC interface (for testing for example) you can stop reading now.

First we apologize for having to introduce a breaking change. We are confident that changes to the query processing APIs will be a very rare event after this time.

This is a decision we have to take given that it'll be even harder to change it in the future and we believe this is a correct leap towards an API that is stable for years to come.

Prior to 0.14, the KV server API is tailored specific to Key-Value retrieval used by the Protected Audience. It implements the V1 and V2 API explained here. And it was designed before the introduction of User Defined Functions. While it is loyal to the key-value nature of the key value server, the server has now evolved into a more generic system that is suitable to do information retrieval and generally stateful request processing inside TEE. With that realization, the RPC API is slightly restructured to be more generic. And the UDF API can have different form ("API overlay") for different use cases. Chrome Protected Audience is one use case.

Although the APIs become more generic, because of the per-use-case API overlay technique used here, the actual impact to Chrome Protected Audience is not as large.

For more information, see API doc.

On a side note, we also published a tutorial for a smoother introduction experience.

Please let us know if you have run into any issues.

[peiwenhu]

Corresponding changes to the Chrome Protected Audience trusted K/V API: https://github.com/WICG/turtledove/pull/900/files