Trace id is not carried forwarded in case of threads() used in route

[PradeepNain]

Hi, We are using sleuth camel.
We get the traces from the API and carry forward the trace in b3 header to camel.
Everything was working fine, but then we started using the threads() in the route, after that all the trace is not getting carried forward and is broken.
We are not able to visualize the traces.

Before: working
from(kafkaProperties)
.routeId(ROUTE_ID)
.process()..

After: Not working
from(kafkaProperties)
.threads()
.executorService(executorService)
.routeId(ROUTE_ID)
.process()..

New traces are getting created per processor

[tdanylchuk]

Unfortunately, multithreading(splitting pipeline) is not supported by this lib, not sure if we going to invest time on that, but any help would be much appreciated.

[PradeepNain]

There are some tests though with threads
https://github.com/Playtika/sleuth-camel/blob/develop/sleuth-camel-core/src/test/java/com/playtika/sleuth/camel/functional/TestApp.java#L87

[PradeepNain]

Found a way
If you use TraceableExecutorService, it carries the trace id across.
https://docs.spring.io/spring-cloud-sleuth/docs/current/reference/html/integrations.html#sleuth-async-executor-service-integration

I'll raise a PR with updated Readme.

TraceableExecutorService traceableExecutorService = new TraceableExecutorService(beanFactory, executorService);

from(kafkaProperties)
.threads()
.executorService(traceableExecutorService)