Manually set baggage is not automatically cleaned up from MDC

I have configured:

spring.sleuth:
  propagation-keys:
    - x-session-id
  log:
    slf4j:
      whitelisted-mdc-keys: x-session-id 

If I pass this propagation key with a value to my app as HTTP header then after the request is completed it is automatically removed from MDC by Slf4jScopeDecorator.

But if I don’t pass it as header but manually set the value somewhere during processing of the request then I have to manually set it to two places:

ExtraFieldPropagation.set(continuedSpan.context(), "x-session-id", "mySession123");
MDC.put("x-session-id", "mySession123");

and I also have to create an Interceptor and manually wipe it from MDC after the request processing has completed by calling: MDC.remove("my-key")

This is because Slf4jScopeDecorator only wipes any baggage that arrived with the request.

I propose to create a mechanism to register the value with single call (so it gets set in both to ExtraFieldPropagation and to MDC) and also after a value has been registered it would be automatically wiped from MDC after the request has completed.

Related StackOverflow post.

[dlsrb6342]

This feature is not released yet I think.

[dlsrb6342]

No. sleuth cannot clear MDC. In current implementation, previousMdc’s key set is consist of whited list keys that have non-null value. But, if you call ExtraFieldPropagation.set(key, value) after TraceWebFilter.filter(), there is no value in ExtraFieldPropagation when Slf4jScopeDecorator decorate current span.