A basic chain template showing the RAG pattern using a vector store on Astra DB.

An Astra DB database is required; free tier is fine.

• You need the database API endpoint (such as https://0123...-us-east1.apps.astra.datastax.com) ...
• ... and a token (AstraCS:...).

Also, an OpenAI API Key is required. Note that out-of-the-box this demo supports OpenAI only, unless you tinker with the code.

Provide the connection parameters and secrets through environment variables. Please refer to .env.template for the variable names.

Assuming you have already created the app (i.e. langchain app new MyApp; cd MyApp), this is what you'll need:

langchain app add --repo "hemidactylus/langserve_astradb_entomology_rag" --branch main

Important: adjust the project's server.py as instructed in the output of the above.

Now, make sure all required environment variables are set, and run

langchain serve

that's it. You can now test the new endpoints by opening http://127.0.0.1:8000/docs, or visiting directly http://127.0.0.1:8000/astradb_entomology_rag/playground/.

Suggestions:

• for a negative test, try Do birds have wings?
• for a positive test, try Do Odonata have wings?

For a standalone usage (outside of langchain serve), clone this repo, cd to its root directory, ensure you set all environment variables, then launch:

poetry install
poetry run python main.py

Note: In a full application, the vector store might be populated in other ways than what done here. The populate step here is done for the demo RAG chains to sensibly work.