class ElasticAPM::OpenTracing::Tracer

def extract(format, carrier)
  case format
  when ::OpenTracing::FORMAT_RACK
    ElasticAPM::TraceContext
      .parse(carrier['HTTP_ELASTIC_APM_TRACEPARENT'])
  else
    warn 'Only extraction from HTTP headers via Rack is available'
    nil
  end
rescue ElasticAPM::TraceContext::InvalidTraceparentHeader
  nil
end