Trace Drains Reference

Trace Drains forward distributed tracing data from your deployments to external endpoints for storage and analysis. You can configure Trace Drains in two ways:

• Custom endpoint: Send traces to any HTTP endpoint you configure
• Native integration: Use integrations from the Vercel Marketplace like Braintrust

Vercel sends traces to endpoints over HTTPS following the OpenTelemetry Protocol (OTLP) specification.

Trace Drains follow the OpenTelemetry traces specification. Vercel automatically adds these specific resource attributes to all traces:

Vercel supports the following formats for Trace Drains. You can configure the format when configuring the Drain destination:

Vercel sends traces as JSON objects following the OpenTelemetry specification:

{ "resourceSpans": [{ "resource": { "attributes": [{ "key": "service.name", "value": { "stringValue": "vercel-function" } }] }, "scopeSpans": [{ "scope": { "name": "vercel" }, "spans": [{ "traceId": "7bba9f33312b3dbb8b2c2c62bb7abe2d", "spanId": "086e83747d0e381e", "name": "GET /api/users", "kind": "server", "startTimeUnixNano": "1694723400000000000", "endTimeUnixNano": "1694723400150000000" }] }] }] }

Vercel sends traces in binary protobuf format following the OTLP/HTTP specification. This format is more efficient for high-volume trace data transmission.

When you configure a Trace Drain in the Vercel UI, you can set the sampling rate to control the volume of data sent. This helps manage costs when you have high traffic volumes.

Custom spans from functions using the Edge runtime are not forwarded via the Trace Drain.

For more information on Trace Drains and how to use them, check out the following resources:

• Drains overview
• Configure Drains
• OpenTelemetry traces specification