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Serverless functions and CLI scripts terminate quickly. Laminar batches spans for performance, which means spans might not be sent before the process exits.

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The Problem

In long-running servers, background batching works fine—spans accumulate and flush periodically. In Lambda or a CLI script, the process may exit before the batch is sent.

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The Solution

Flush before exit. Call the flush method at the end of your handler or script. This sends all pending spans synchronously. In Python, use force_flush() for serverless specifically—it ensures spans are sent even when daemon threads would be terminated.

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When to Flush

ScenarioAction
Web server (long-running)Nothing needed—batching works
CLI scriptFlush at the end
Lambda / serverlessFlush at the end of each invocation
Graceful shutdownShutdown the SDK
Don’t flush in hot paths (e.g., inside a web request handler). It adds latency. Flush only when the process is about to exit.

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Examples

import { Laminar } from '@lmnr-ai/lmnr';

Laminar.initialize();

// ... your work ...

// End of script / serverless handler
await Laminar.flush();

// Or: flush + release resources
await Laminar.shutdown();
See also: Laminar.flush and Laminar.shutdown

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Python Serverless Caveat (Why force_flush() Exists)

In Python, Laminar.flush() triggers the export, but the export itself runs in a background thread. In short-lived processes (like Lambda), the process can exit before that thread completes, and spans can be lost. Laminar.force_flush() blocks until export completes by internally resetting the tracing pipeline, so it’s the safest option at the end of each serverless invocation.