Demonstrates how to retrieve child span metrics based on trace-level metadata in Braintrust

20250617_get_child_span_based_on_trace_metadata.py

"""
This script demonstrates how to retrieve child span metrics based on trace-level metadata.
Given a project ID and a specific span name, it queries the Braintrust API to find
traces matching certain metadata criteria and extracts metrics for the specified child span.
"""

import argparse
import os
import requests
from dotenv import load_dotenv

load_dotenv(override=True)

# Make sure to replace this with your stack's Universal API URL if you are self-hosting
API_URL = "https://api.braintrust.dev/"
headers = {"Authorization": "Bearer " + os.environ["BRAINTRUST_API_KEY"]}
 
 
if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("--project-id", type=str, required=True)
    parser.add_argument("--span-name", type=str, default="root")
    args = parser.parse_args()
 
    # Find all rows matching a certain metadata value.
    query= f"""
    select: span_attributes, metrics
    from: project_logs('{args.project_id}') traces
    filter: metadata.orgName = 'qawolf'
    limit:10
    """
    
    response = requests.post(f"{API_URL}/btql", headers=headers, json={"query": query}).json()

    durations = []
    for trace in response["data"]:
        # print(trace)
        
        if trace["span_attributes"]["name"] == args.span_name:
            metrics = trace["metrics"]
            if metrics.get("end") and metrics.get("start"):
                duration = metrics['end'] - metrics['start']
                durations.append(duration)
                print(f"Duration: {duration}ms")
                print("-"*100)
        
            else:
                print("Start or end not found for this span")
                print("-"*100)
        
    print(f"\nAverage duration: {sum(durations)/len(durations)}ms\n")