Web browser span exporters should support navigator.sendBeacon

[danwild]

When a web browser compatible span exporter package is developed, it will need a way to reliably ensure any open spans are ended and exported when user navigates away from the browser window (for context - I've just been experimenting crudely with wiring up zipkin exporter to jaeger via HTTP POST and realised this is a problem).

Historically, web developers have used work-arounds leveraging the unload / beforeunload window events, however these are clearly smelly and unreliable.

I would be nicer if such a package could play nicely with the navigator.sendBeacon method.

By design, navigator.sendBeacon must execute the async request itself, so to support this - we probably just need exporter to expose methods for:

• returning endpoint used for span reporting
• returning spans payload (formatted ready to send to the endpoint)

e.g.

window.addEventListener("unload", logData, false);

function logData() {
  const serviceUrl = myExporter.getServiceUrl();
  const payload = myExporter.getPayload();
  navigator.sendBeacon(serviceUrl, payload);
}

[danwild]

Worth noting that sendBeacon has limitations on transmission format due to security issues, e.g. application/json which might make things a little tricky.

[obecny]

@danwild thx for pointing this out. There is not yet dedicated exporter for a web browser - this is going to be implemented in near future.

[draffensperger]

Yeah, I think the main challenge here is how to encode the spans in the beacon well, but I think this is a good idea!

[bradfrosty]

I believe this issue can be closed, @openetelemetry/exporter-collector has been implemented and supports navigator.sendBeacon().

[obecny]

done already