chore(sample-app): langserve example app

[nirga]

• I have added tests that cover my changes.
• If adding a new instrumentation or changing an existing one, I've added screenshots from some observability platform showing the change.
• PR name follows conventional commits format: feat(instrumentation): ... or fix(instrumentation): ....
• (If applicable) I have updated the documentation accordingly.

[damianoneill]

@nirga would it be possible to include in the README.md a couple of examples of what you expect to see in the trace? I connected traceloop as follows:

try:
    Traceloop.init(
        app_name="Langchain Chatbot Application",
        api_endpoint="http://localhost:4318", # http endpoint for opentelemetry (jaeger) collector
        disable_batch=True,
    )
except Exception as e:  # pylint: disable=broad-except
    logger.error("Failed to initialize Traceloop: %s", e)

And started up a Jaeger container as follows:

docker run --name jaeger \
  -e COLLECTOR_ZIPKIN_HOST_PORT=:9411 \
  -p 5775:5775/udp \
  -p 6831:6831/udp \
  -p 6832:6832/udp \
  -p 5778:5778 \
  -p 16686:16686 \
  -p 14250:14250 \
  -p 14268:14268 \
  -p 14269:14269 \
  -p 9411:9411 \
  -p 4318:4318 jaegertracing/all-in-one:latest

When I generate a langchain invoke, I can see the LLM call per below.

I'm not sure what is expected to be shown, I didn't see any calls for langchain itself, e.g. the Runnable Fastapi calls; invoke, stream, etc. Should I have seen these? Or should I only see the LLM call?

Thanks,
Damian.

[nirga]

@damianoneill yes I think we should! Mind opening a bug for that so we'll take care of it!
But to answer you now - you should be able to see chains and runnables. Let's discuss this over an issue / discussions or slack and try to understand what's not working for you