The Galileo LangChain integration allows you to automatically log all LangChain interactions with LLMs, including prompts, responses, and performance metrics. This integration works through LangChain’s callbacks API, making it easy to add logging to your existing LangChain applications with minimal code changes.

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Installation

First, make sure you have the Galileo SDK and LangChain installed:

pip install galileo langchain

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Setup

Create or update a .env file with your Galileo API key and other optional settings:

# Scoped to an Organization
GALILEO_API_KEY=...

# Optional, set a default Project
GALILEO_PROJECT=...
# Optional, set a default Log Stream
GALILEO_LOG_STREAM=...

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Basic Usage

The integration is based on the GalileoCallback class, which implements LangChain’s callback interface. To use it, simply create an instance of the callback and pass it to your LangChain components:

from galileo.handlers.langchain import GalileoCallback
from langchain_openai import ChatOpenAI
from langchain.schema import HumanMessage

# Create a callback handler
callback = GalileoCallback()

# Initialize the LLM with the callback
llm = ChatOpenAI(model="gpt-4o", temperature=0.7, callbacks=[callback])

# Create a message with the user's query
messages = [HumanMessage(content="What is LangChain and how is it used with OpenAI?")]

# Make the API call
response = llm.invoke(messages)

print(response.content)

When initializing the GalileoCallback, you can optionally specify a Galileo logger instance or control trace behavior:

from galileo import GalileoLogger
from galileo.handlers.langchain import GalileoCallback

# Create a custom logger
logger = GalileoLogger(project="my-project", log_stream="my-log-stream")

# Create a callback with the custom logger
callback = GalileoCallback(
    galileo_logger=logger,  # Optional custom logger
    start_new_trace=True,   # Whether to start a new trace for each chain
    flush_on_chain_end=True # Whether to flush traces when chains end
)

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Using with LangChain Chains

You can also use the callback with LangChain chains. Make sure to pass the callback to both the LLM and the chain:

from galileo.handlers.langchain import GalileoCallback
from langchain.chains import LLMMathChain
from langchain_openai import ChatOpenAI

# Create a callback handler
handler = GalileoCallback()

# Initialize the LLM with the callback
llm = ChatOpenAI(model="gpt-4o", callbacks=[handler])

# Initialize the chain with the callback
llm_math = LLMMathChain.from_llm(llm, callbacks=[handler])

# Invoke the chain with the callback and additional metadata
result = llm_math.invoke(
    "What's 2 + 2?",
    {
        "callbacks": [handler],
        "metadata": {
            "galileo_session": "my-session",
            "galileo_user_id": "user-id",
        },
    },
)

print(result)

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Advanced Usage

The GalileoCallback captures various LangChain events, including:

  • LLM starts and completions
  • Chat model interactions
  • Chain executions
  • Tool calls
  • Retriever operations
  • Agent actions

For each of these events, the callback logs relevant information to Galileo, such as:

  • Input prompts and messages
  • Output responses
  • Model information
  • Timing data
  • Token usage
  • Error information (if any)

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Adding Metadata

You can add custom metadata to your logs by including it in the metadata parameter when invoking a chain or LLM:

result = chain.invoke(
    "Your input here",
    {
        "callbacks": [handler],
        "metadata": {
            "user_id": "user-123",
            "session_id": "session-456",
            "custom_field": "custom value"
        }
    }
)

This metadata will be attached to the logs in Galileo, making it easier to filter and analyze your data.

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Nested Chains and Agents

The GalileoCallback automatically handles nested chains and agents, creating a hierarchical trace that reflects the structure of your LangChain application:

from galileo.handlers.langchain import GalileoCallback
from langchain.agents import AgentExecutor, create_react_agent
from langchain.tools import Tool
from langchain_openai import ChatOpenAI

# Create a callback handler
handler = GalileoCallback()

# Initialize the LLM with the callback
llm = ChatOpenAI(model="gpt-4o", callbacks=[handler])

# Define tools
tools = [
    Tool(
        name="Calculator",
        func=lambda x: eval(x),
        description="Useful for when you need to calculate something"
    )
]

# Create an agent
agent = create_react_agent(llm, tools, "You are a helpful assistant.")
agent_executor = AgentExecutor.from_agent_and_tools(
    agent=agent,
    tools=tools,
    callbacks=[handler]
)

# Run the agent
result = agent_executor.invoke(
    {"input": "What is 2 + 2?"},
    {"callbacks": [handler]}
)

print(result["output"])

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Best Practices

  1. Pass callbacks consistently: Make sure to pass the callback to all LangChain components (LLMs, chains, agents, etc.) to ensure complete logging.

  2. Include meaningful metadata: Add relevant metadata to your invocations to make it easier to filter and analyze your logs.

  3. Use with galileo_context: You can combine the LangChain integration with galileo_context for more control over trace management:

from galileo import galileo_context
from galileo.handlers.langchain import GalileoCallback
from langchain_openai import ChatOpenAI

with galileo_context(project="my-project", log_stream="my-log-stream"):
    callback = GalileoCallback()
    llm = ChatOpenAI(model="gpt-4o", callbacks=[callback])
    # Your LangChain code here