Minimal custom datadog distributed tracing

datadog_distribute_tracing.rb

# Following datadog patterns, see:
# https://github.com/DataDog/dd-trace-rb/blob/master/lib/datadog/tracing/contrib/karafka/distributed/propagation.rb
# https://github.com/DataDog/dd-trace-rb/blob/master/lib/datadog/tracing/contrib/karafka/patcher.rb#L27-L49
class MyCustomPropagation < Datadog::Tracing::Distributed::Propagation
  def initialize(
    propagation_style_inject:,
    propagation_style_extract:,
    propagation_extract_first:
  )
    super(
      propagation_styles: {
        Datadog::Tracing::Configuration::Ext::Distributed::PROPAGATION_STYLE_B3_MULTI_HEADER =>
        Datadog::Tracing::Distributed::B3Multi.new(fetcher: Datadog::Tracing::Distributed::Fetcher),
          Datadog::Tracing::Configuration::Ext::Distributed::PROPAGATION_STYLE_B3_SINGLE_HEADER =>
        Datadog::Tracing::Distributed::B3Single.new(fetcher: Datadog::Tracing::Distributed::Fetcher),
          Datadog::Tracing::Configuration::Ext::Distributed::PROPAGATION_STYLE_DATADOG =>
        Datadog::Tracing::Distributed::Datadog.new(fetcher: Datadog::Tracing::Distributed::Fetcher),
          Datadog::Tracing::Configuration::Ext::Distributed::PROPAGATION_STYLE_TRACE_CONTEXT =>
        Datadog::Tracing::Distributed::TraceContext.new(fetcher: Datadog::Tracing::Distributed::Fetcher),
          Datadog::Tracing::Configuration::Ext::Distributed::PROPAGATION_STYLE_NONE => Datadog::Tracing::Distributed::None.new
      },
      propagation_style_inject: propagation_style_inject,
      propagation_style_extract: propagation_style_extract,
      propagation_extract_first: propagation_extract_first
    )
  end
end

class MyClass
  def initialize(idx, propagation)
    @idx = idx
    @propagation = propagation
  end

  def call(data = {})
    digest = @propagation.extract(data)
    Datadog::Tracing.continue_trace!(digest) if digest

    Datadog::Tracing.trace("my_class_trace_#{@idx}") do
      puts "active trace/span: #{Datadog::Tracing.active_trace.id} / #{Datadog::Tracing.active_span&.id}".yellow

      @propagation.inject!(Datadog::Tracing.active_trace.to_digest, data)
    end

    data
  end
end

propagation = MyCustomPropagation.new(
  propagation_style_inject: Datadog.configuration.tracing.propagation_style_inject,
  propagation_style_extract: Datadog.configuration.tracing.propagation_style_extract,
  propagation_extract_first: Datadog.configuration.tracing.propagation_extract_first
)
data = MyClass.new(1, propagation).call({})
data = MyClass.new(2, propagation).call(data)
data = MyClass.new(3, propagation).call(data)

# output:
# active trace/span: 138574660423656517896910447203791200371 / 2743717933204636498
# active trace/span: 138574660423656517896910447203791200371 / 456627744106024901
# active trace/span: 138574660423656517896910447203791200371 / 4372616340251457109