Propogate a span across micro services

[asadcompro11]

I have a use case where I want to start a span for a trace in one service and then, without closing the span, navigate to a second service (used window.location.href for navigation). In the second service, I want to resume the existing span and close it there, rather than creating a child span. While I know how to propagate a trace across services using the traceparent, I want to know if it is possible to propagate a span as well.

[sayedrisat]

You cannot resume the same Span object in another service. A span is one timed operation; across a process boundary, propagate its SpanContext (traceparent and, when present, tracestate) and create a new span in the next service. That new span keeps the trace ID and uses the upstream span ID as its parent. If you need a causal link without a parent/child relationship, use a span link instead.

On the receiving side, extract the propagated context and start a new span with it as parent:

const parentContext = propagation.extract(ROOT_CONTEXT, incomingHeaders);

await tracer.startActiveSpan('service.operation', {}, parentContext, async span => {
  try {
    await doWork();
  } finally {
    span.end();
  }
});

A plain window.location.href navigation does not let browser JavaScript attach custom request headers, so fetch/XHR auto-instrumentation will not propagate context on that document navigation. The application/server needs to carry the W3C trace context to the next page (or use an instrumented request instead); then the next service can extract it. Avoid passing the Span object itself.

References: Span and SpanContext model, JavaScript context propagation.