Simple datadog trace parser/debugger

config.ru

# frozen_string_literal: true

# Simple datadog trace parser/debugger
#
# To run, simply:
# $ rackup -p 8126

require 'roda'
require 'pry'
require 'msgpack'
require 'json'

class HumanizeId
  def initialize(prefix)
    @prefix = prefix
    @last_id = 0
    @ids = {}
  end

  def call(id)
    return if Integer(id) == 0

    @ids[id] ||= "#{@prefix}#{@last_id += 1}"
  end
end

class App < Roda
  plugin :json
  @@raw_traces = []
  @@parsed_traces = []

  @@trace_humanizer = HumanizeId.new("t")
  @@span_humanizer = HumanizeId.new("s")

  RELEVANT_DD_META_TAGS = %w[water kafka karafka messag work consum produc].freeze

  route do |r|
    r.get 'info' do
      {}
    end
    r.get 'raw_traces' do
      @@raw_traces
    end
    r.get 'parsed_traces' do
      spans = @@parsed_traces.dup
      spans_by_parent_id = spans
        .group_by { |span| span[:parent_id] }
        .transform_values do |child_spans|
          child_spans.sort_by { |span| span[:start] }
        end
      spans.each do |span|
        span[:children] = spans_by_parent_id[span[:span_id]] || []
      end

      spans_by_parent_id.except(nil).select { |_, v| v.empty? }.each_pair do |parent_id, spans|
        warn "No parent span (id: #{parent_id}) found. #{spans.size} spans are children of it"
      end

      spans_by_parent_id[nil] || []
    end
    r.post('v0.4/traces') do
      trace_batches = MessagePack.unpack(request.body.read)
      trace_batches.each do |trace_batch|
        trace_batch.each do |trace|
          @@raw_traces << trace

          duration_ms = (Integer(trace["duration"]) * 1e-6).round(2)
          start = Time.at(Integer(trace["start"]) * 1e-9)

          @@parsed_traces << {
            start: start.strftime("%F %T.%3N"),
            duration: "#{format(duration_ms.to_s, "%.2f")}ms",

            trace_id: @@trace_humanizer.(trace["trace_id"]),
            span_id: @@span_humanizer.(trace["span_id"]),
            parent_id: @@span_humanizer.(trace["parent_id"]),

            operation_name: trace["name"],
            resource_name: trace["resource"],
            service: trace["service"],

            meta: trace["meta"].select do |k, _|
              RELEVANT_DD_META_TAGS.any? { |word| k.downcase.include?(word) }
            end.transform_keys(&:to_sym),

            span_links: trace["span_links"].map do |span_link|
              {
                trace_id: @@trace_humanizer.(span_link["trace_id"]),
                span_id: @@span_humanizer.(span_link["span_id"]),
              }
            end
          }
        end
      end
      {success: true}
    end
  end
end

run App.freeze.app