Overriding Spring cloud sleuth Trace Id format - spring-boot

Question

We are looking at leveraging spring cloud sleuth for distributed tracing and we've worked on a POC. It seems like a great solution, works out of the box.
Had a follow up question though:
We use random UUID vs 64 bit ids as trace id. We understand that custom headers (A new trace Id for example) can be added along with sleuth headers but would it be possible to override the default trace id format for slueth? We have looked through the documentation and perhaps Propagation is
the way to go. Can someone who has done this point us in the right direction and to some examples if possible. The help would be much appreciated.
We are using the latest release 2.0.1 which uses the brave library.
Any help/pointers would be greatly appreciated.
Thanks,
GK

Answer 1

Spring-sleuth doesn't provide a way to override the default ID's. According to OpenZipkin, 'Trace identifiers are 64 or 128-bit, but all span identifiers within a trace are 64-bit. All identifiers are opaque'
Refer this:
https://github.com/openzipkin/b3-propagation#identifiers
So, You can either put the generated request ID as Tag ('tag':'requestID') or You can place generate UID in a different field and use propagation technique. Refer ExtraFieldPropagationTest for reference.
https://github.com/openzipkin/brave/blob/master/brave/src/test/java/brave/propagation/ExtraFieldPropagationTest.java

Answer 2

Even though this is not possible (afaik), if your use case is to use custom headers for log correlation, all that's needed is setting these properties (Related SO Answer):
# To add request-id (to MDC?) via sleuth
spring.sleuth.baggage.correlation-fields=x-request-id
spring.sleuth.baggage.remote-fields=x-request-id
And then this can be used in your logging pattern:
%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%X{traceId:-},%X{spanId:-},%X{x-request-id:-}] [%thread] %logger{40} : %msg%n
Now along with the built-in traceId & spanId, the value of the header x-request-id will also be logged:
2022-06-28 19:55:40.071 WARN [8add19deba73c0f3,cda65c8122e5e025,some-request-id] [reactor-http-epoll-8] c.i.p.g.s.MyService : My warn log
To make this more concise, you can skip traceId & spanId if not required. A better way could have been to use them as a fallback when your own custom correlation header is not available, but logback currently does not (and probably will not) support nesting default values for MDC.

Answer 3

What you can do is to generate the id in a different field and propagate it further on. Check this part of the documentation https://cloud.spring.io/spring-cloud-static/Finchley.SR1/single/spring-cloud.html#_propagating_extra_fields
52.1 Propagating extra fields Sometimes you need to propagate extra fields, such as a request ID or an alternate trace context. For
example, if you are in a Cloud Foundry environment, you might want to
pass the request ID, as shown in the following example:
// when you initialize the builder, define the extra field you want to
propagate Tracing.newBuilder().propagationFactory(
ExtraFieldPropagation.newFactory(B3Propagation.FACTORY,
"x-vcap-request-id") );
// later, you can tag that request ID or use it in log correlation
requestId = ExtraFieldPropagation.get("x-vcap-request-id"); You may
also need to propagate a trace context that you are not using. For
example, you may be in an Amazon Web Services environment but not be
reporting data to X-Ray. To ensure X-Ray can co-exist correctly,
pass-through its tracing header, as shown in the following example:
tracingBuilder.propagationFactory(
ExtraFieldPropagation.newFactory(B3Propagation.FACTORY,
"x-amzn-trace-id") ); [Tip] In Spring Cloud Sleuth all elements of the
tracing builder Tracing.newBuilder() are defined as beans. So if you
want to pass a custom PropagationFactory, it’s enough for you to
create a bean of that type and we will set it in the Tracing bean.