Exploring the Real-Time Streaming Capabilities of StructuredOutputParser

[Brayan233]

Hello, Langchain community and maintainers,

I'm currently exploring the StructuredOutputParser class and its capabilities. I have a specific use case in my React application where I'm handling real-time JSON streaming data.

Current Implementation:

In my React application, I've developed a custom hook (useJsonStreamParser) that listens to a stream of JSON-like strings. It uses React's useEffect and useRef hooks to maintain a buffer and state.

The hook does the following:

• Keeps a running buffer (bufferRef) to hold incoming JSON-like strings.
• Utilizes a state (isInsideValueRef) to determine whether the buffer is currently inside a JSON value for a given key.
• Processes new data (processCompletion) to append it to the existing buffer.
• Identifies the start (checkForJsonStart) and end (checkForJsonEndAndSetValue) of a JSON value for a specific key and updates a state variable in real time.

Questions:

1. Does StructuredOutputParser have capabilities for real-time streaming? Could it be used to process a stream of JSON strings in real time?

2. If it does support streaming, how would one go about implementing this feature?

3. Could StructuredOutputParser potentially be a drop-in replacement for my custom function?

4. I would love to hear your thoughts and insights on this. This discussion could be beneficial for anyone looking to leverage Langchain for real-time data streaming and parsing.

Thank you!

[dosubot[bot]]

🤖

Hello,

Thank you for your interest in the LangChain project and for your detailed question.

Based on the current functionality of the StructuredOutputParser class, it is primarily designed to parse structured output from language models. It does this by taking the output from a language model and returning an object where each key-value pair represents a question and its answer.

To answer your questions:

1. As per the current implementation and the available documentation, the StructuredOutputParser does not inherently support real-time streaming of JSON data. It is designed to parse structured output from language models, and there is no explicit mention of streaming capabilities.

2. Given the current design of the StructuredOutputParser, implementing real-time streaming would likely require significant modifications to the class. This would involve changing the parse method to handle streaming data and potentially adding new methods to handle buffering and state management.

3. As for whether StructuredOutputParser could be a drop-in replacement for your custom function, it's hard to say without more details about your function and its requirements. However, given the current functionality of StructuredOutputParser, it seems unlikely without modifications.

4. I agree that a discussion on this topic could be beneficial. Real-time data streaming and parsing is a complex and important topic, and it would be interesting to explore how LangChain could be adapted to support it.

Please note that while I've done my best to provide accurate information based on the current state of the LangChain codebase, there may be plans to add such functionality in the future or there may be aspects of the codebase that I've overlooked. I would recommend keeping an eye on the repository for updates and potentially opening a feature request if real-time streaming is a functionality you'd like to see in LangChain.

I hope this helps, and please don't hesitate to ask if you have any further questions.

Best regards,
Dosu

Sources

• langchain/src/output_parsers/tests/structured.int.test.ts
• langchain/src/output_parsers/structured.ts

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[tfactor2]

I'm new to langchain, just experimenting. Having similar requirements: want a stream data from the "chat-conversational-react-description" agent.

I sketched that:

const regex = /"action"\: \"Final Answer\".+\n\s*\"action_input\"\: \"(.+?)\"?$/g;
let buf = '', lastResult = '';
const res = await executor.call({ input: line }, [
    {
        handleLLMNewToken(token: string) {
            buf += token;
            const match = regex.exec(buf);
            const finalResultMaybe = match?.[1];
            let resultToken = '';
            if (finalResultMaybe) {
                resultToken = finalResultMaybe.substring(lastResult.length);
                lastResult = finalResultMaybe;
            }
            
            process.stdout.write(resultToken);
        },
    },
]);

The idea is to continuously parse the output string and try to find the "Final Answer" pattern. As soon it is found, the resulting token can be retrieved as a diff between the last and the current state.
It could be integrated into a parser or something similar.

WDYT?