add uber-trace-id for request header

[aslongyouloveme]

so microservice can get this for inherit span

[pavolloffay]

@aslongyouloveme could you please help me understand this change and describe why it is needed?

The request already contains span context. This span context was used as a parent to span created in the subscribe method.

[aslongyouloveme]

I used springcloud-gateway as the gateway, and downstream order-to-service is a micro service, gateway is a webflux application, and order-to-service is a servlet application. When I integrated jaeger, order-to-service could not get spancontext of gateway, because header (ude-trace-id) was not added in the forwarded request header. @

[aslongyouloveme]

@pavolloffay

[pavolloffay]

It sounds fine, thanks for the explanation. Could you write a test for the functionality you are adding?

[aslongyouloveme]

I would like to write a test case for it, I did not find any specimen test case for ‘TracingOperator.java’.
It seams difficult to mock ServerWebExchange that has so much method,
e.g this.exchange.mutate().request(req).build(), req.mutate().header(key, map.get(key))
Could you please give me some help?

[pavolloffay]

I am more interested in integration test. There are some for webflux which should use this class.