There are some cases where one might need to enable/disable tracing for certain children spans. For example, if I will write a bunch of files in a zip stream, I want to trace the call to S3 to list the files but not every single call to S3 to retrieve the content of the file. In such case I want to make a decision on what to record and what not based on rules in the spans.

For implementation reference we could have a look at brave: https://github.com/openzipkin/brave/blob/master/brave/src/main/java/brave/handler/FinishedSpanHandler.java

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