core[patch]: Fix RemoteRunnable streaming when used in sequences, add tracing

[rahilvora]

This PR is trying to solve issue where RemoteRunnable object does not support streaming with RunnableSequence

Code Flow
RunnableSequence and RemoteRunnable both the classes extends Runnable class

Runnable class has implementation of stream. Now, const chain = RunnableSequence.from([prompt, model]) returns RunnableSequence object. chain.stream would call stream function on Runnable class (parent class) as RunnableSequence class (child class) does not have stream function on it.

Now, stream function in Runnable class calls this._streamIterator . In this context, this is RunnableSequence , Hence it will call _streamIterator of RunnableSequence.

_streamIterator calls object.transform function, which calls transform function of Runnable class. transform function internally calls this._streamIterator again. Now, this is object context which is RemoteRunnable

But, in case of RemoteRunnable object (which is passed as model in above example), does not have implementation of _streamIterator function hence it calls _streamIterator of parent class i.e. Runnable class which internally is yielding invoke (this.invoke(input, options);. Hence, this calls RemoteRunnable invoke function.

Fix

We need to override _streamIterator for RemoteRunnable class, so that it yield stream instead of invoke.

Fixes #4811

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[jacoblee93]

Thanks for this!

Would be good to add a test confirming the fix?

[jacoblee93]

This should test streaming usage in a chain though? That's what the issue was about:

#4811

e.g.

const chain = prompt.pipe(remote).stream();

[rahilvora]

I thought I would just test _streamIterator function which I added. But, I think what you said make sense. Let me try with chain.

[rahilvora]

Updated!!

[jacoblee93]

Thanks!