Should omit ParentSpanId header for root spans

[sullerandras]

There are services which throw error when an empty X-B3-ParentSpanId header sent with the HTTP request.

From the openzipkin specification:

The X-B3-ParentSpanId header must be present on a child span and absent on the root span.

How to reproduce

conn = Faraday.new() do |faraday|
  faraday.use ZipkinTracer::FaradayHandler, 'service_name'
  faraday.request :url_encoded
  faraday.adapter Faraday.default_adapter
end
conn.get('http://logs-01.loggly.com/inputs/TOKEN/tag/http/')

Result is 400 Bad request.

If we don't send tracing headers, the response is the expected 403 Invalid API key:

conn = Faraday.new() do |faraday|
  faraday.request :url_encoded
  faraday.adapter Faraday.default_adapter
end
conn.get('http://logs-01.loggly.com/inputs/TOKEN/tag/http/')

Workaround

The only workaround i found so far is to monkey patch FaradayHandler with unless trace_id.send(method).to_s.empty? as below:

require 'zipkin-tracer/faraday/zipkin-tracer'
module ZipkinTracer
  class FaradayHandler < ::Faraday::Middleware
    def call(env)
      trace_id = TraceGenerator.new.next_trace_id
      TraceContainer.with_trace_id(trace_id) do
        b3_headers.each do |method, header|
          env[:request_headers][header] = trace_id.send(method).to_s unless trace_id.send(method).to_s.empty?
        end
        if Trace.tracer && trace_id.sampled?
          trace!(env, trace_id)
        else
          @app.call(env)
        end
      end
    end
  end
end

[codefromthecrypt]

Closed as not an issue?

[sullerandras]

I don't think I closed this. This is definitely an issue. Please reopen it.

…

On 31 Aug 2017 3:36 p.m., "Adrian Cole" ***@***.***> wrote: Closed as not an issue? — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#115 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAYEdvP-pYEM4i_TLHuFP9oOEC0UbLu4ks5sdmJygaJpZM4PIQWc> .