nginx_filter_responseMsec value zero

[longpan]

nginx_vts_exporter version: 0.10.3

config:
` #nginx_vts_module状态监控模块
vhost_traffic_status_zone;
vhost_traffic_status_filter_by_set_key $uri $server_name;

server {
    listen 9999;
    server_name localhost;

    location /status {
        allow 127.0.0.1;
        deny all;
        vhost_traffic_status_display;
        vhost_traffic_status_display_format html;
    }
}`

nginx_vts_exporter_build_info{branch="HEAD",goversion="go1.10",revision="8aa2881c7050d9b28f2312d7ce99d93458611d04",version="0.10.3"}

all the meric: nginx_filter_responseMsec value is zero;