Adding `langfuse` library as a dependency

Run this command in a terminal, in your project's directory:

cargo add langfuse

To add it manually, edit your project's Cargo.toml file and add to the [dependencies] section:

langfuse = "0.1.8"

The langfuse library will be automatically available globally. Read the langfuse library documentation.

Back to the crate overview.

Readme

Langfuse Rust Client

A non official open-source Rust client for tracking simple interactions with Langfuse (https://langfuse.com) the open-source LLM observability platform.

This Rust crate has been serving as a critical component in Neura AI's backend infrastructure (https://meetneura.ai), adopted across more than 20 applications over the past 8 months. After repeatedly duplicating it, I've decided to share with the amazing Rust community, empowering developers to effectively monitor and optimize their LLM-based applications.

Features

Track user interactions with LangFuse
Handle both successful and error cases
Configure LangFuse API settings
Support for custom trace names
Track tokens used and model name
Track processing time
Flexible metadata and observation tracking

Installation

Type this inside your project directory

cargo add langfuse

Or if you prefer to use a Cargo.toml file: Add this to your Cargo.toml:

[dependencies]
Langfuse = "0.1.7"

Usage

Basic example:

use langfuse::{LangFuseConfig, send_interaction};

#[tokio::main]
async fn main() {
    let config = LangFuseConfig::new(
        "your-public-key",
        "your-secret-key",
        "https://cloud.langfuse.com",
    );

    let result = send_interaction(
        &config,
        "request-id-123",
        Some("user-1"), 
        Some("session-1"),
        "Hello, who are you?", 
        "I'm an AI assistant, ready to help you",
        "here should be full raw response", 
        100, 
        false,
        Some("model-x"), 
        Some(TokenUsage {
            input_tokens: 100,
            output_tokens: 900,
            total_tokens: 1000,
        }),
        Some("json_endpoint_request_trace"), 
    ).await;

    match result {
        Ok(_) => println!("Successfully tracked interaction"),
        Err(e) => eprintln!("Error tracking interaction: {}", e),
    }
}

API Documentation

`LangFuseConfig`

Configuration for LangFuse API credentials and endpoint.

pub struct LangFuseConfig {
    pub public_key: String,
    pub secret_key: String,
    pub base_url: String,
}

impl LangFuseConfig {
    pub fn new(public_key: &str, secret_key: &str, base_url: &str) -> Self;
}

`send_interaction`

Track an interaction with LangFuse.

pub async fn send_interaction(
    config: &LangFuseConfig,
    request_id: &str,
    user_id: Option<&str>,
    session_id: Option<&str>,
    input: &str,
    output: &str,
    raw_response: Option<&str>,
    processing_time_ms: u128,
    is_error: bool,
    model_name: Option<&str>,
    token_usage: Option<TokenUsage>,
    trace_name: Option<&str>,
) -> Result<(), LangFuseTrackerError>;

// TokenUsage structure for detailed token tracking
pub struct TokenUsage {
    pub input_tokens: u32,
    pub output_tokens: u32,
    pub total_tokens: u32,
}

`LangFuseTrackerError`

Error types for LangFuse tracking operations.

pub enum LangFuseTrackerError {
    InvalidCredentials,
    NetworkError(reqwest::Error),
    InvalidResponseFormat,
    JsonParseError(serde_json::Error),
    InvalidTimestampFormat,
    InvalidBaseUrlFormat,
    Unknown(String),
}

Project Structure

langfuse_tracker/
├── src/
│   ├── lib.rs
│   ├── client.rs
│   ├── error.rs
│   ├── types.rs
│   └── utils/
│       └── mod.rs
├── example/
│   └── usage.rs
├── tests/
│   └── integration.rs

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for details. If you have any questions or suggestions, please contact open an issue or a pull request on https://github.com/adolfousier/langfuse-rust

License

This project is licensed under the MIT License - see the LICENSE file for details.

Adding langfuse library as a dependency

Adding `langfuse` library as a dependency