Implement Response Streaming

[carlodek]

Motivation and Context (Why the change? What's the scenario?)

Add option to stream Ask result tokens without waiting for the full answer to be ready.

High level description (Approach, Design)

• New stream boolean option for the Ask API, false by default. When true, answer tokens are streamed as soon as they are generated by LLMs.
• New MemoryAnswer.StreamState enum property: Error, Reset, Append, Last.
• If moderation is enabled, the content is validated at the end. In case of moderation failure, the service returns an answer with StreamState = Reset and the new content to show to the end user.
• Streaming uses SSE message format.
• By default, SSE streams end with a [DONE] token. This can be disabled via KM settings.
• SSE payload is optimized, returning RelevantSources only in the first SSE message.

Example request:

curl 'http://127.0.0.1:9001/ask' --header 'Content-Type: application/json' \
    --data '{"question": "which storage engines can I use with Kernel Memory?", "stream": true }'

Response:

data: {"streamState":"append","question":"which storage engines can I use with Kernel Memory?","noResult":false,"text":"","relevantSources":[... cut ...]}

data: {"streamState":"append","noResult":false,"text":"The"}

data: {"streamState":"append","noResult":false,"text":" storage"}

data: {"streamState":"append","noResult":false,"text":" engines"}

data: {"streamState":"append","noResult":false,"text":" that"}

[...]

data: {"streamState":"append","noResult":false,"text":"work"}

data: {"streamState":"append","noResult":false,"text":" in"}

data: {"streamState":"append","noResult":false,"text":" progress"}

data: {"streamState":"append","noResult":false,"text":")"}

data: [DONE]

[carlodek]

@microsoft-github-policy-service agree

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[dluc]

Update: for this feature to be merged, there's a couple of things to do:

• Check this similar PR Implement new streaming ask endpoint (WIP) #400 and decide which approach to take
• Support content moderation. The stream of tokens needs to be validated while streamed, on a configurable frequence. If at any point the text moderation fails, the stream needs to be reset, e.g. sending a special token or similar.

[nurkmez2]

I have been waiting for a long time if you could add Ask Stream Endpoint in the next version, it would be great

[nurkmez2]

Hi @carlodek
It would be great if you could complete the feature of ask_stream endpoint.
Thanks and Regards

[roldengarm]

Any updates on this please @dluc it has been a long time, hopefully we can get this sorted soon.

[carlodek]

Hello, I've noticed that your work works like a charm with Ollama too! Still with Ollama Stream call is working with ask_stream endpoint. @dluc let me know if I have to do something more

[dluc]

There are several changes out of scope and unnecessary ones, plus some affecting the solution security. First thing I would ask is to undo all these changes, including code style ones, limiting to the bare minimum. Thanks!

[dluc]

I'll make some changes to see if we can merge it:

• move the [DONE] token at the end of the stream, separate from the stream chunks
• merge stream behavior into the existing /ask endpoint, using an optional boolean flag to choose whether to stream or not
• remove code duplication in SearchClient
• revisit how content moderation is implemented