Proxy_cache_use_stale updating

Server NGINX
1

I’ve one storage server using nginx, one cache file server using nginx.
The following are my configuration files:

  1. storage_server.conf(ip address 192.168.1.10):
    server {
    listen 80;
    listen [::]:80 ipv6only=on;
    server_name _;
location / {
    return 403;
}

location ~ ^/cache/ {
root /var/my_file_storage;
directio 1m;
directio_alignment 8k;
output_buffers 1 1m;
try_files $request_uri =404;
}
}

  1. cache_server.conf(ip address 192.168.1.2):
    proxy_cache_path /nginx-cache/cache-level1/cache levels=1
    keys_zone=CacheLVL1:10m inactive=12h max_size=5G;
    server {
    listen 80;
    listen [::]:80 ipv6only=on;
    server_name _;
location / {
    return 403;
}

location ~ ^/cache/ {
    proxy_pass              http://192.168.1.10:80$request_uri; #

request_uri is path to file on Storage server.
proxy_cache CacheLVL1;
proxy_cache_key $request_uri;
proxy_cache_valid 200 30d;
proxy_temp_path /nginx-cache/cache-level1/temp;
proxy_cache_use_stale updating;
proxy_max_temp_file_size 0;
add_header X-Proxy-Cache $upstream_cache_status;
proxy_set_header Range $http_range;
proxy_set_header If-Range $http_if_range;
}
}
/etc/nginx/nginx.conf
…{
…
log_format upstreamlog ‘[$time_local] $remote_addr to $upstream_addr
$upstream_cache_status’;
access_log /var/log/nginx/cache.log upstreamlog;
…
}

I’ve read about proxy_cache_use_stale updating. But I do not understand
how its activities:
1.
http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache_use_stale:
the updating parameter permits using a stale cached response if it is
currently being updated. This allows minimizing the number of accesses
to proxied servers when updating cached data.
2. Proxy_cache_use_stale - NGINX - Ruby-Forum “If I understand this
right if I use proxy_cache_use_stale updating and
If I have 1000 users trying to access expired cached information. It
will only send one request to backend server to update the cache ?”

I request multiple times and received multiple files in the
/nginx-cache/cache-level1/temp folder 000000xx format. I think I have
the wrong configuration in my configuration file because it works unlike
what I’ve read. I never saw the $ upstream_cache_status UPDATING in
cache.log.
It is related to X-Accel-Expires “,” Expires “,” Cache-Control "is not?
Can someone explain to proxy_cache_use_stale updating your help, Thank!