nginx访问日志每5秒显示一次HEAD请求

Question

我有一个Django Gunicorn Nginx设置，可以正常运行，但nginx访问日志每5秒包含以下行：

10.112.113.1 - - [09/Jan/2019:05:02:21 +0100] "HEAD / HTTP/1.1" 302 0 "-" "-"

此日志记录事件中的信息量非常稀少，但是每5秒302必须与nginx配置相关吗？

我的nginx配置如下：

http {
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                  '$status $body_bytes_sent "$http_referer" '
                  '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;
    keepalive_timeout   65;
    types_hash_max_size 2048;

    include             /etc/nginx/mime.types;
    default_type        application/octet-stream;

    include /etc/nginx/conf.d/.conf;

    upstream app_server {
        server unix:/path_to/gunicorn.sock fail_timeout=0;
    }

    server {
        server_name example.com;
        listen 80;
        return 301 https://example.com$request_uri;
    }

    server {
        listen 443;
        listen [::]:443;

        server_name example.com;

        ssl on;
        ssl_certificate /path/cert.crt;
        ssl_certificate_key /path/cert.key;

        keepalive_timeout 5;
        client_max_body_size 4G;

        access_log /var/log/nginx/nginx-access.log;
        error_log /var/log/nginx/nginx-error.log;

        location /static/ {
            alias /path_to/static/;
        }
        location /media/ {
            alias /path_to/media/;
        }
        include /etc/nginx/mime.types;

        # checks for static file, if not found proxy to app
        location / {
            try_files $uri @proxy_to_app;
        }

        location @proxy_to_app {
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto https;
            proxy_set_header Host $host;
            proxy_redirect off;
            proxy_pass http://app_server;
        }
    }
}