Use of LiteLLM Router for load balancing and fallbacks

[denisergashbaev]

As DSPy is using LiteLLM internally, I wonder how to use the LiteLLM router. In particular, I would like to add load balancing and fallbacks via LiteLLM.

Another example. LiteLLM provides rate limit aware routing strategy that routes the call to the deployment with the lowest tokens per minute value (see BerriAI/litellm#4510, https://docs.litellm.ai/docs/routing#advanced---routing-strategies-%EF%B8%8F). I would want to use the router

Thank you

[okhat]

Thanks! Maybe just launch their server and connect to it via the client dspy.LM? i.e., DSPy doesn't need to be invovled

[okhat]

Link: https://github.com/stanfordnlp/dspy/blob/main/examples/migration.ipynb

[denisergashbaev]

Thank you, Omar! I think it makes sense to expose router of LiteLLM as well. Under some circumstances, one would not want to run a separate proxy server and prefer using the LiteLLM Router for fallbacks, load balancing, and request prioritization

[okhat]

@denisergashbaev Sorry, I'm mistaken about the nature of the LiteLLM router. I assumed it was inherently a proxy.

It's actually just a client-side thing, indeed: https://docs.litellm.ai/docs/routing

[okhat]

Yes, I think we should support this. It seems like we should inherit dspy.LM and just accept a list of models instead of one model. This seems cool. Do you need this soon? We'd certainly appreciate a PR.

[zhaohan-dong]

Down to work on this if needed. @okhat maybe another function in dspy.LM similar to litellm_completion? Can also do a router kwarg to pass in a litellm.Router object.

[okhat]

@zhaohan-dong Thanks a lot! How do you envision the interface looking like? Let's agree on the right API before doing anything intensive :D

[zhaohan-dong]

Exactly what I hoped to ascertain I think litellm tries to have similar signature for Router as the plain generation methods. So I'm thinking it could be progressively do dependency injection as first step:

• An argument router: Optional[litellm.Router] = None
• If router != None, the inference call would invoke router.text_completion()
• If model not in the router's model_list, throw error (Not 100% this is the cleanest way)

Otherwise could inherit LM with AnotherClass(model_list=model_list, **kwargs), so people who wnat to use the router would use that, and not affecting other users. Not sure what's the best naming/file to put it in.

Happy to proceed either way or do something else you'd suggest.

Fundamentally I see the plain litellm.text_generation() as a special case of Router.text_generation(), where there's only one model in the model_list.

[okhat]

Thanks a lot @zhaohan-dong ! I like the idea of a class that inherits from dspy.LM

[zhaohan-dong]

Awesome! Maybe RoutedLM as name?