headers_to_add {
  header {
    key: "x-header"
    value: "%UPSTREAM_METADATA([\"ns\", \"key\"])%"
  }
}
stream_info {
  start_time: 1522796769123
  upstream_metadata {
    filter_metadata {
      key: "ns"
      value: {
        fields {
          key: "key"
          value: { string_value: "value" }
        }
      }
    }
  }
}
