How to add custom attribute with aws-otel-nodejs layer configured for nodejs lambda?

[spongenee]

Hi we are using the aws-otel-nodejs layer for auto instrumentation of our nodejs lambda app and traces are sent to aws XRay. We would like to add custom attributes to the traces. Is that possible while continuing to use the layer?

More specifically, will the following code work?

const { trace } = require("@opentelemetry/api");

function handleUser(user) {
  let activeSpan = trace.getActiveSpan();
  activeSpan.setAttribute("user.id", user.getId());
}

[shreyanshjain1]

Yes, that should generally be possible.

Using the aws-otel-nodejs layer for auto-instrumentation does not stop you from also using the OpenTelemetry API in your own code to enrich the current span with custom attributes.

So the basic idea you showed is the right one:

const { trace } = require("@opentelemetry/api");

function handleUser(user) {
  const activeSpan = trace.getActiveSpan();
  if (activeSpan) {
    activeSpan.setAttribute("user.id", user.getId());
  }
}

The main thing I’d add is the null check, because getActiveSpan() can return nothing if that code runs outside an active traced context.

So the short answer is:

• yes, you can keep using the AWS OTel Node.js layer
• yes, you can still add custom attributes in app code
• just make sure you are doing it while the relevant span is active

If you find that activeSpan is sometimes missing, then the next thing to check would be where in the Lambda execution flow that code runs, because context propagation matters there.

So in practice, your approach is fine — just make it a bit more defensive with if (activeSpan).

[spongenee]

thank you for your suggestion!!