class ElasticAPM::ContextBuilder

def get_headers_and_env(rack_env)
  # In Rails < 5 ActionDispatch::Request inherits from Hash
  headers =
    rack_env.respond_to?(:headers) ? rack_env.headers : rack_env
  headers.each_with_object([{}, {}]) do |(key, value), (http, env)|
    next unless key == key.upcase
    if key.start_with?('HTTP_')
      http[camel_key(key)] = value
    else
      env[key] = value
    end
  end
end