[Go] proposal: revised API

[jba]

In this API, configuration (defining actions) should still happen
at the beginning of the program, but can be done incrementally by
calling functions on a plugin. For example:

err := googleai.Init(...)   // creates state common to all actions
m1 := googleai.DefineModel("gemini-1.0-pro")
e1 := googleai.DefineEmbedder("emb-01")

When everything has been configured, the program must call genkit.Init.
This has two effects:

• Attempts to register additional actions will fail.
• The dev server is started.

This API combines the convenience and clarity of building and storing
actions individually with the requirement that everything that the
program needs is registered early.

DO NOT SUBMIT. Implementation is incomplete. For discussion only.

[jba]

I believe this is complete and correct.

Open questions:

• For vector DB plugins, it's not clear whether the indexer and retriever should be defined separately, as I've done for pinecone, or together, as I did for localvec. A separate DefineIndexer and DefineRetriever is more in keeping with the rest of the API, but provides an opportunity for different args to be passed, which would give rise to confusing bugs. But if one function is used, users who only want one of the two actions must nevertheless get both. It's also unclear what to name the function. In localvec I called it DefineStore, but that would be an odd name for pinecone, since it doesn't use that term anywhere else.

• genkit.Init is designed so the default (passing nil) provides a good experience. But its behavior with arguments is complicated. Is there a simpler design?

[ianlancetaylor]

A vector DB plugin is useless if you don't have both an indexer and a retriever, so I would vote for defining them together. Maybe DefineVectorStore or DefineDataStore? I don't think it matters that Pinecone doesn't use those terms.

[jba]

I imagine that it would be common in larger setups to have one process doing the indexing, in the background as it were, while the frontend retrieves. Much like pkgsite or indeed Google Search.

[ianlancetaylor]

Fair enough.

[jba]

@pavelgj Can you comment? I believe this is the design we discussed over VC. I want to make sure you're OK with it before proceeding.