langchain/docs/tracing/local_installation.md

Locally Hosted Setup

This page contains instructions for installing and then setting up the environment to use the locally hosted version of tracing.

Installation

1. Ensure you have Docker installed (see Get Docker) and that it’s running.

2. Install the latest version of langchain: pip install langchain or pip install langchain -U to upgrade your existing version.

3. Run langchain-server. This command was installed automatically when you ran the above command (pip install langchain).

   1. This will spin up the server in the terminal, hosted on port 4137 by default.
   2. Once you see the terminal output langchain-langchain-frontend-1 | ➜ Local: [http://localhost:4173/](http://localhost:4173/), navigate to http://localhost:4173/

4. You should see a page with your tracing sessions. See the overview page for a walkthrough of the UI.

5. Currently, trace data is not guaranteed to be persisted between runs of langchain-server. If you want to persist your data, you can mount a volume to the Docker container. See the Docker docs for more info.

6. To stop the server, press Ctrl+C in the terminal where you ran langchain-server.

Environment Setup

After installation, you must now set up your environment to use tracing.

This can be done by setting an environment variable in your terminal by running export LANGCHAIN_HANDLER=langchain.

You can also do this by adding the below snippet to the top of every script. IMPORTANT: this must go at the VERY TOP of your script, before you import anything from langchain.

import os
os.environ["LANGCHAIN_HANDLER"] = "langchain"