Build RAG Chatbot with LangChain, Faiss, OpenAI GPT-4o, and Ollama nomic-embed-text

Introduction to RAG

Retrieval-Augmented Generation (RAG) is a game-changer for GenAI applications, especially in conversational AI. It combines the power of pre-trained large language models (LLMs) like OpenAI’s GPT with external knowledge sources stored in vector databases such as Milvus and Zilliz Cloud, allowing for more accurate, contextually relevant, and up-to-date response generation. A RAG pipeline usually consists of four basic components: a vector database, an embedding model, an LLM, and a framework.

Key Components We'll Use for This RAG Chatbot

This tutorial shows you how to build a simple RAG chatbot in Python using the following components:

LangChain: An open-source framework that helps you orchestrate the interaction between LLMs, vector stores, embedding models, etc, making it easier to integrate a RAG pipeline.
Faiss: also known as Facebook AI Similarity Search, is an open-source vector search library that allows developers to quickly search for semantically similar multimedia data within a massive dataset of unstructured data. (If you want a much more scalable solution or hate to manage your own infrastructure, we recommend using Zilliz Cloud, which is a fully managed vector database service built on the open-source Milvus and offers a free tier supporting up to 1 million vectors.)
OpenAI GPT-4o: This advanced model from OpenAI focuses on generating highly coherent and contextually relevant text. With enhanced understanding of nuanced language, it excels in creative writing, conversational agents, and educational content. Ideal for applications needing in-depth responses and creativity, GPT-4o offers versatility across various industries.
Ollama nomic-embed-text: This model specializes in generating high-quality text embeddings, designed to enhance semantic understanding in various NLP tasks. Its strengths lie in contextual representation and scalability, making it suitable for applications like semantic search, recommendation systems, and clustering. Ideal for developers looking to integrate profound text analysis into their projects.

By the end of this tutorial, you’ll have a functional chatbot capable of answering questions based on a custom knowledge base.

Note: Since we may use proprietary models in our tutorials, make sure you have the required API key beforehand.

Step 1: Install and Set Up LangChain

%pip install --quiet --upgrade langchain-text-splitters langchain-community langgraph

Step 2: Install and Set Up OpenAI GPT-4o

pip install -qU "langchain[openai]"

import getpass
import os

if not os.environ.get("OPENAI_API_KEY"):
  os.environ["OPENAI_API_KEY"] = getpass.getpass("Enter API key for OpenAI: ")

from langchain.chat_models import init_chat_model

llm = init_chat_model("gpt-4o", model_provider="openai")

Step 3: Install and Set Up Ollama nomic-embed-text

pip install -qU langchain-ollama

from langchain_ollama import OllamaEmbeddings

embeddings = OllamaEmbeddings(model="nomic-embed-text")

Step 4: Install and Set Up Faiss

pip install -qU langchain-community

from langchain_community.vectorstores import FAISS

vector_store = FAISS(embedding_function=embeddings)

Step 5: Build a RAG Chatbot

Now that you’ve set up all components, let’s start to build a simple chatbot. We’ll use the Milvus introduction doc as a private knowledge base. You can replace it with your own dataset to customize your RAG chatbot.

import bs4
from langchain import hub
from langchain_community.document_loaders import WebBaseLoader
from langchain_core.documents import Document
from langchain_text_splitters import RecursiveCharacterTextSplitter
from langgraph.graph import START, StateGraph
from typing_extensions import List, TypedDict

# Load and chunk contents of the blog
loader = WebBaseLoader(
    web_paths=("https://milvus.io/docs/overview.md",),
    bs_kwargs=dict(
        parse_only=bs4.SoupStrainer(
            class_=("doc-style doc-post-content")
        )
    ),
)

docs = loader.load()

text_splitter = RecursiveCharacterTextSplitter(chunk_size=1000, chunk_overlap=200)
all_splits = text_splitter.split_documents(docs)

# Index chunks
_ = vector_store.add_documents(documents=all_splits)

# Define prompt for question-answering
prompt = hub.pull("rlm/rag-prompt")


# Define state for application
class State(TypedDict):
    question: str
    context: List[Document]
    answer: str


# Define application steps
def retrieve(state: State):
    retrieved_docs = vector_store.similarity_search(state["question"])
    return {"context": retrieved_docs}


def generate(state: State):
    docs_content = "\n\n".join(doc.page_content for doc in state["context"])
    messages = prompt.invoke({"question": state["question"], "context": docs_content})
    response = llm.invoke(messages)
    return {"answer": response.content}


# Compile application and test
graph_builder = StateGraph(State).add_sequence([retrieve, generate])
graph_builder.add_edge(START, "retrieve")
graph = graph_builder.compile()

Test the Chatbot

Yeah! You've built your own chatbot. Let's ask the chatbot a question.

response = graph.invoke({"question": "What data types does Milvus support?"})
print(response["answer"])

Example Output

Milvus supports various data types including sparse vectors, binary vectors, JSON, and arrays. Additionally, it handles common numerical and character types, making it versatile for different data modeling needs. This allows users to manage unstructured or multi-modal data efficiently.

Optimization Tips

As you build your RAG system, optimization is key to ensuring peak performance and efficiency. While setting up the components is an essential first step, fine-tuning each one will help you create a solution that works even better and scales seamlessly. In this section, we’ll share some practical tips for optimizing all these components, giving you the edge to build smarter, faster, and more responsive RAG applications.

LangChain optimization tips

To optimize LangChain, focus on minimizing redundant operations in your workflow by structuring your chains and agents efficiently. Use caching to avoid repeated computations, speeding up your system, and experiment with modular design to ensure that components like models or databases can be easily swapped out. This will provide both flexibility and efficiency, allowing you to quickly scale your system without unnecessary delays or complications.

Faiss Optimization Tips

To enhance the performance of the Faiss library in a Retrieval-Augmented Generation (RAG) system, begin by selecting the appropriate index type based on your data volume and query speed requirements; for example, using an IVF (Inverted File) index can significantly speed up queries on large datasets by reducing the search space. Optimize your indexing process by using the nlist parameter to partition data into smaller clusters and set an appropriate number of probes (nprobe) during retrieval to balance between speed and accuracy. Ensure the vectors are properly normalized and consider using 16-bit or 8-bit quantization during indexing to reduce memory footprints for large datasets while maintaining reasonable retrieval accuracy. Additionally, consider leveraging GPU acceleration if available, as Faiss highly benefits from parallel processing, leading to faster nearest neighbor searches. Continuous fine-tuning and benchmarking with varying parameters and configurations can guide you in finding the most efficient setup specific to your data characteristics and retrieval requirements.

OpenAI GPT-4o optimization tips

GPT-4o is optimized for speed and efficiency, making it an excellent choice for high-performance RAG applications. Maximize efficiency by refining retrieval strategies—use reranking methods to prioritize the most relevant documents before passing them to the model. Reduce token consumption by keeping retrieved context concise and ensuring prompts follow a structured format. Adjust temperature (0.1–0.2) for precise, fact-based responses while increasing it slightly for creative or exploratory tasks. Optimize response speed by leveraging OpenAI’s API streaming capabilities, reducing latency for real-time applications. Implement prompt templates to standardize inputs and reduce variability in responses. Use hybrid search (combining keyword and vector search) for more accurate and contextually relevant retrieval. Regularly monitor API latency and response consistency, adjusting retrieval parameters dynamically for optimal performance.

Ollama nomic-embed-text optimization tips

Ollama nomic-embed-text is designed for robust text embedding generation, making it essential to optimize how embeddings are stored and queried in a RAG pipeline. Preprocess input text by stripping unnecessary metadata and normalizing case to maintain consistency. Choose an optimized vector indexing strategy, such as IVF-PQ for balanced speed and accuracy, depending on dataset size. Use approximate nearest neighbor search to accelerate retrieval while maintaining a high recall rate. Cache commonly accessed embeddings to avoid redundant computations. If embeddings are used for long-term retrieval tasks, periodically refresh and retrain on new data to prevent model drift. Optimize database queries to quickly retrieve relevant embeddings and minimize I/O bottlenecks.

By implementing these tips across your components, you'll be able to enhance the performance and functionality of your RAG system, ensuring it’s optimized for both speed and accuracy. Keep testing, iterating, and refining your setup to stay ahead in the ever-evolving world of AI development.

RAG Cost Calculator: A Free Tool to Calculate Your Cost in Seconds

Estimating the cost of a Retrieval-Augmented Generation (RAG) pipeline involves analyzing expenses across vector storage, compute resources, and API usage. Key cost drivers include vector database queries, embedding generation, and LLM inference.

RAG Cost Calculator is a free tool that quickly estimates the cost of building a RAG pipeline, including chunking, embedding, vector storage/search, and LLM generation. It also helps you identify cost-saving opportunities and achieve up to 10x cost reduction on vector databases with the serverless option.

Calculate your RAG cost now.

Calculate your RAG cost

What Have You Learned?

What have you learned? Well, you’ve taken a big step into the exciting world of Retrieval-Augmented Generation (RAG) systems! Throughout this tutorial, you've seen how each component contributes to building a powerful system that can redefine how we interact with data. The framework we explored serves as the backbone—tying together the various elements seamlessly, ensuring that everything functions in perfect harmony. With the vector database, like Faiss, at your fingertips, you now have the ability to perform lightning-fast searches through your data, making it easier than ever to find the right information when you need it.

But that's not all! The integration of a large language model, such as OpenAI's GPT-4o, breathes conversational life into your applications, allowing you to generate human-like responses and engage users in meaningful dialogues. Combined with an embedding model like Ollama’s nomic-embed-text, you can create rich semantic representations, enabling your system to truly understand and contextualize information.

Remember the optimization tips and the cost calculator we discussed? Those tools are there to help you streamline performance while keeping an eye on efficiency. So, what’s next? Dive in! Start building, optimizing, and innovating your own RAG applications! The possibilities are endless, and you have all the knowledge you need to create something extraordinary. Let your creativity soar, and don’t hesitate to push the boundaries of what’s possible. Happy building!

Further Resources

🌟 In addition to this RAG tutorial, unleash your full potential with these incredible resources to level up your RAG skills.

How to Build a Multimodal RAG | Documentation
How to Enhance the Performance of Your RAG Pipeline
Graph RAG with Milvus | Documentation
How to Evaluate RAG Applications - Zilliz Learn
Generative AI Resource Hub | Zilliz

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