Current behaviour

Rails callbacks (before/after) are not a part of the action span.
In the before_action callback, active_span is:

SpanOperation(name:rack.request,sid:1008860920845926479,tid:1866324838581500214,pid:0)

But in the action call:

SpanOperation(name:rails.action_controller,sid:3701457545195306293,tid:1866324838581500214,pid:1008860920845926479)

Expected behaviour

active_pack spans should include the callbacks. That could be done either through a separate span or by extending the current one.

I'm raising this as a bug rather than a feature request, because otherwise we end up in situations where (for example) rack seems to own spans from active_record, which is not true:

Those queries are made in the before_action on the controller.

This is also very important when trying to name the spans something more specific - for example when a top level ApiController that other things inherit knows how to label the span in before_action, but delegating that to all specific Api implementations would be extremely repetitive.

Steps to reproduce

class SomeController < ApplicationController
  before_action :bar

  def foo
    Datadog::Tracing.trace("this.goes.in.controller") {}
  end

  private
  
  def bar
    Datadog::Tracing.trace("this.goes.in.rack") {}
  end
end

Environment

• ddtrace version: 1.1.0
• Configuration block (Datadog.configure ...):

    c.tracing.instrument :rails, service_name: 'marketplace'
    c.tracing.instrument :rack, request_queuing: true, web_service_name: 'marketplace-rack'

• Ruby version: 2.7
• Operating system: linux
• Relevant library versions: