utils.rb

module Tracer::Utils
  def push_span(span)
    RequestStore.store[:tracer_spans] ||= []
    RequestStore.store[:tracer_spans].push(span)
  end

  def pop_span
    RequestStore.store[:tracer_spans] ||= []
    RequestStore.store[:tracer_spans].pop
  end

  def peek_span
    RequestStore.store[:tracer_spans] ||= []
    RequestStore.store[:tracer_spans][-1]
  end

  def trace_block(name, tags: {}, &_block)
    parent = peek_span
    # TODO: if parent is nil here, check to see if we have a request to extract
    # headers from
    span = OpenTracing.start_span(
      name,
      child_of: parent,
      tags: tags
    )
    push_span span

    yield span
  ensure
    pop_span
    span&.finish
  end

  # This sets a bunch tags that end up being backend-specific.
  def extract_request_tags(req)
    base = {
      'http.method' => req.request_method,
      'http.host' => req.host_with_port,
      'http.request.size' => req.content_length,
      'http.path' => req.path,
      # 'http.url' => req.url, # Can reveal secrets, so not included by default.
      'http.request.user_agent' => req.user_agent,
      'http.request.xhr' => req.xhr?
    }

    req.params.each do |key, val|
      v = case key
            when 'password', 'old_password', 'new_password', 'api_key'
              '<FILTERED>' # Zipkin doesn't escape its input?!
            else
              val_s = val.to_s
              CGI.escape(val_s) # Srsly, why doesn't zipkin html escape its input?
          end

      base["param.#{key}"] = v
    end

    base
  end

  module_function :push_span, :pop_span, :peek_span, :trace_block, :extract_request_tags
end