Support for config_sentence_transformers.json

[sam-ulrich1]

Feature request

Add cli option to auto-format input text with config_sentence_transformers.json prompt settings (if provided) before toknizing.

Motivation

A lot of models now expect a prompt prefix so enabling the server-side handle of this allows clients to become model "model-agnostic". We have trouble changing between models since we must support the custom prompt for each specific model on the client side. Server side via config would remove this entriely.

Your contribution

Happy to do the PR myself just want to make sure this would be a welcome contribution

[OlivierDehaene]

Good idea. This could be added to the payload of /embed.
Do you have an example of such a model I could test this feature with?

[sam-ulrich1]

I'll have to back track what I was working on at the time I made this but yes. This was derived from a need so I just have to go find the model. I'm still happy to offer a PR just wanted to make sure it was welcome before putting the work in

[sam-ulrich1]

Here's and example @OlivierDehaene
https://huggingface.co/Snowflake/snowflake-arctic-embed-l/tree/main

[OlivierDehaene]

So you want to be able to select the prompt with a payload like:

{
  "inputs": "text",
  "prompt": "query"
  "truncate": false
}

And the prompt is just added at the beginning of inputs right?

[sam-ulrich1]

My preference order would be

1. Option for the router to load the config and auto format the prompt. Issue here being some prompts are conditional so there would have to be some query param that instructs to format or not. Benefit being that the end application does not have to manage any formatting.
2. End application passes the prompt format like you described above with some predefined formatting structure. Issue here is that end applications must be aware which creates a "model-lock-in" situation that makes it hard to change embedding models.

Basically we find it a bit limiting to have to change code across multiple codebases when we change models

[OlivierDehaene]

Ok so what you would like is to have a default format set when starting the service? Otherwise I don't see how you can make it truly model agnostic.
All models can chose whatever format and name they want for this parameter and you need to be able to specifiy it when embedding.

So:

1. parse the config
2. set auto format from parameter in cli
3. embed with default format or specified format in the body

[sam-ulrich1]

Yes. The main goal would be to reduce friction between model changes. If y'all are comfortable with this, I'd be happy to offer a PR. It will be a few weeks with the holiday and all.

[OlivierDehaene]

The main goal would be to reduce friction between model changes

I don't know how much it reduces friction because the models don't need to agree on the names.
For example:

Snowflake/snowflake-arctic-embed-l

"prompts": {
    "query": "Represent this sentence for searching relevant passages: "
  }

vs

intfloat/e5-mistral-7b-instruct

"prompts": {
    "web_search_query": "Instruct: Given a web search query, retrieve relevant passages that answer the query\nQuery: ",
    "sts_query": "Instruct: Retrieve semantically similar text.\nQuery: ",
    "summarization_query": "Instruct: Given a news summary, retrieve other semantically similar summaries\nQuery: ",
    "bitext_query": "Instruct: Retrieve parallel sentences.\nQuery: "
  }

In this case you still need to be aware of the different names and what they do. However it's still easier to just pick and add the correct enum value to the body and leave to TEI to add the pre-prompt than what you currently have to do so I'm in favour of adding it. I will do that quickly.

[OlivierDehaene]

A first draft: #312