how to enable zipkin tracing

Having some trouble seeing spans sent to zipkin server when enabling tracing support using OpenTracing API on Openwhisk. Once zipkin configuration is uncommented in application.conf, is there a specific point when traces are supposed to be sent to the server?

Start with the tracing configuration in application.conf and the OpenTracing integration mentioned in the issue. Determine when spans are expected to be sent to the Zipkin server, then document that behavior and the relevant configuration steps so a user can verify tracing is working.

Written by the indexing model from the issue text.