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Applies to:


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Summary

Issue: Traces display empty fields or remain “in progress” indefinitely. Cause: Application terminates before flush() completes or spans aren’t properly ended, particularly in serverless/container environments. Resolution: Explicitly call flush() before termination and ensure all spans are ended.

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Resolution Steps

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Python

with logger.start_span(name="operation") as span:
    span.log(input=input_data, output=output_data, metadata=metadata)
    # span.end() called automatically

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TypeScript

await logger.traced(async (span) => {
  span.log({ input: inputData, output: outputData, metadata });
  // span.end() called automatically
});

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Step 2: Call flush() explicitly before process exit

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Python

def cleanup_braintrust():
    try:
        project.logger.flush()  # Blocks until upload completes
    except Exception:
        logging.exception("Failed to flush Braintrust project")

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TypeScript

async function cleanupBraintrust() {
  try {
    await project.logger.flush(); // Waits until upload completes
  } catch (error) {
    console.error("Failed to flush Braintrust project:", error);
  }
}

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Key Points

  • flush() waits for completion
  • Context managers automatically call span.end()
  • Manual spans: call span.end() in finally blocks or they remain incomplete
  • For serverless functions, call flush() before the handler returns