end def trace(env, &block)
span = Span.new("authentication", generate_span_id)
span.record(SERVER_RECV)
status, headers, body = yield
ensure
span.record(SERVER_SEND)
end https://github.com/openzipkin/zipkin-ruby/blob/master/lib/zipkin-tracer/rack/zipkin-tracer.rb Execute the app Received a request Sending back
to the client Non-pseudocode version: