Modify the Application: How?

[ewolff]

https://linkerd.io/2/tasks/distributed-tracing/ "Modify the Application" doesn't give details about how the application should be modified and why:

• Some tracing header must be passed on to outgoing requests. Which?
• In addition, some headers might be added to see how much time is spent in the application itself.
  • However, that should be optional, correct? But the code uses the collector i.e. the application does report its time spans. The documentation should state that this is optional, if it is.
  • It should be explained how the time spans are reported. Which headers? Is there some standard?

Background: I am trying to do the same with a Spring Sleuth based application and find it hard to understand how this can be done.