Opentelemetry Span <> Logger integration

config.exs

import Config

config :opentelemetry,
  processors: [
    {OpentelemetrySpanLogger, []},
    :batch
  ]

opentelemetry_span_logger.ex

defmodule OpentelemetrySpanLogger do
  require Record
  @behaviour :otel_span_processor

  @span_record Record.extract(:span, from_lib: "opentelemetry/include/otel_span.hrl")
  Record.defrecord(:span, @span_record)

  @impl :otel_span_processor
  def force_flush(_config), do: :ok

  @impl :otel_span_processor
  def on_start(_ctx, span, _config) do
    Logger.metadata([trace_id: span(span, :trace_id), span_id: span(span, :span_id)])
    span
  end

  @impl :otel_span_processor
  def on_end(_span, _config), do: true
end