Allow custom mappings for different models

[fedefernandez]

Model URI Adapter

This PR adds support for different models based on the path and model in the request. With this, you can quickly start a new endpoint and redirect all the traffic for a particular path (chat completion, embeddings, ...) to a specific endpoint instead of OpenAI.

Example 1

Let's say we want to use a custom model for the embeddings.

1. Prepare the embedding endpoint

One of the easiest ways to do it is to use huggingface/text-embeddings-inference.

Text Embeddings Inference (TEI) is a toolkit for deploying and serving open source text embeddings models. TEI enables high-performance extraction for the most popular models, including FlagEmbedding, Ember, GTE and E5.

One of the tools that TEI provides is a multi-purpose docker image to ramp up a server. Since TEI supports the Bert model, we can use BAAI/llm-embedder. Starting this model locally is as easy as running the following command:

docker run -p 9090:80 -v /tmp/gf-data:/data --pull always ghcr.io/huggingface/text-embeddings-inference:cpu-0.3.0 --model-id BAAI/llm-embedder --revision main

• /tmp/gf-data is a shared volume with the Docker container to avoid downloading weights every run
• text-embeddings-inference:cpu-0.3.0 uses the Docker image for running locally in CPU. We have others available
• BAAI/llm-embedder is the model
• main is the repo revision. It can be a tag and a commit also.

The Docker image will bump a server with a series of endpoints. One of them is fully compatible with the OpenAI API:

• https://huggingface.github.io/text-embeddings-inference/#/Text%20Embeddings%20Inference/openai_embed

2. Install the Ktor client plugin

The second step is to install the Ktor client plugin to redirect requests to the local embedding endpoint. We want to redirect all the requests to "/v1/embeddings" with the model BAAI/llm-embedder to the recently created endpoint:

• http://localhost:9090/openai

To install the plugin and configure the Ktor client plugin, we need to add the following code in the client's initialization:

xef/server/src/main/kotlin/com/xebia/functional/xef/server/Server.kt

Lines 56 to 63 in 21f0f4a

	HttpClient(CIO) {
	engine {
	requestTimeout = 0 // disabled
	}
	install(Auth)
	install(Logging) { level = LogLevel.INFO }
	install(ClientContentNegotiation)
	}

install(com.xebia.functional.xef.server.http.client.ModelUriAdapter) {
  addToPath(
    com.xebia.functional.xef.server.http.client.OpenAIPathType.EMBEDDINGS,
    "BAAI/llm-embedder" to "http://localhost:9090/openai"
  )
}

Example 2

Redirecting chat completion requests is quite similar. Let's imagine we have a local proxy running a gpt-3.5-turbo in the following address:

• http://localhost:8080/chat/completions

The necessary code for redirecting the requests will be:

install(com.xebia.functional.xef.server.http.client.ModelUriAdapter) {
  addToPath(
    com.xebia.functional.xef.server.http.client.OpenAIPathType.CHAT,
    "gpt-3.5-turbo" to "http://localhost:8080/chat/completions"
  )
}

Notes

Future improvements could use headers as input for the URI/model map. Also, the map is currently set in code, but we could use DB to fill that information.

This works as a reverse proxy without modifying the request/response. The next step will be to have a new component that could adapt requests/responses to APIs that are not OpenAI compatible (like MLflow). The full interaction is represented in the following diagram.

sequenceDiagram
    Client->>ModelUriAdapter: Path + Model
    ModelUriAdapter->>ModelReqResAdapter: Request
    ModelReqResAdapter->>Model: Request
    Model->>ModelReqResAdapter: Response
    ModelReqResAdapter->>Client: Response

[raulraja]

🙌 great work @fedefernandez !