buster/api/libs/braintrust/README.md

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# Braintrust Client Library
A Rust client library for interacting with the [Braintrust](https://braintrust.dev) API, allowing for logging of spans and traces to track AI application performance.
## Features
- Asynchronous logging of spans to Braintrust
- Hierarchical tracing with parent-child relationships
- Automatic timing and duration calculation
- Token counting for LLM calls
- Custom metadata and attributes
- Background logging with non-blocking API
## Usage
Add the library to your project's dependencies:
```toml
[dependencies]
braintrust = { path = "../libs/braintrust" }
```
### Basic Example
```rust
use braintrust::{BraintrustClient, TraceBuilder};
use serde_json::json;
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
// Initialize the client with your API key and project ID
let client = BraintrustClient::new("YOUR_API_KEY", "YOUR_PROJECT_ID");
// Create a trace for the entire process
let trace = TraceBuilder::new(client.clone(), "My AI Application");
// Create a span for an LLM call
let mut span = trace.add_span("GPT-4 Call", "llm").await?;
// Update the span with input and output
span = span
.set_input(json!({
"messages": [{"role": "user", "content": "Hello, world!"}]
}))
.set_output(json!({
"choices": [{"message": {"role": "assistant", "content": "Hi there!"}}]
}))
.set_tokens(10, 5)
.add_metadata("model", "gpt-4");
// Log the updated span
client.log_span(span).await?;
// Finish the trace
trace.finish().await?;
Ok(())
}
```
### Creating Spans
Spans represent a single operation or step in your application. You can create spans directly or through a `TraceBuilder`:
```rust
// Create a span directly
let span = Span::new("My Operation", "function", "root_span_id", Some("parent_span_id"));
// Or create a span through a trace builder
let span = trace.add_span("My Operation", "function").await?;
// Create a child span with a parent reference
let child_span = trace.add_child_span("Child Operation", "function", &parent_span).await?;
```
### Updating Spans
Spans are immutable, but methods return a new span with updated fields:
```rust
let updated_span = span
.set_input(json!({ "key": "value" }))
.set_output(json!({ "result": "success" }))
.set_tokens(50, 30)
.add_metadata("important_context", "some value");
```
### Logging Spans
Spans can be logged asynchronously (non-blocking) or synchronously:
```rust
// Asynchronous logging (non-blocking)
client.log_span(span).await?;
// Synchronous logging (waits for API response)
client.log_span_sync(span).await?;
```
## Advanced Usage
See the examples directory for more advanced usage patterns:
- `basic_usage.rs`: Simple example of logging spans and traces
- `conversation_tracking.rs`: Example of tracking a conversation with LLM calls
## Testing
Run the tests with:
```bash
cargo test -p braintrust
```
## License
MIT