class ElasticAPM::OpenTracing::Tracer

def extract(format, carrier)
  case format
  when ::OpenTracing::FORMAT_RACK
    SpanContext.from_header(
      carrier['HTTP_ELASTIC_APM_TRACEPARENT']
    )
  when ::OpenTracing::FORMAT_TEXT_MAP
    SpanContext.from_header(
      carrier['elastic-apm-traceparent']
    )
  else
    warn 'Only extraction from HTTP headers via Rack or in ' \
      'text map format are available'
    nil
  end
rescue ElasticAPM::TraceContext::InvalidTraceparentHeader
  nil
end