proxy_cache_use_stale updating; doesn't work

nguyennhatkhang2704 · 2015-09-09T10:20:10+00:00

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proxy_cache_use_stale updating; doesn't work

nguyennhatkhang2704

Hi,
My model consists of 2 server:
1. Cache server: using nginx it function caching file when Storage server respond.
2. Storage server: using nginxit function storage files.

Here are my 2 configuration files:
1.Cache server config(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://192.168.1.3:80$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;
    }
}

2. Storage server config(ip address 192.168.1.3):

server {
    listen      80;
    listen [::]:80 ipv6only=on;
    server_name _;

    location / {
        return 403;
    }
   location ~ ^/cache/ {
        root /var/mystorage;
        directio 1m;
        directio_alignment 8k;
        output_buffers 1 1m;
        try_files $request_uri =404;
   }
}

When I request to cache server with cmd "curl -I http://192.168.1.2/cache/path/to/file" , I received one response has X-Proxy-Cache are MISS, then I checked in directory / a / a, I saw one of the form tmp file 0000001 (this is the file that I had sent in $reuqest_uri). Next I sent one request and I also received one response has X-Proxy-Cache is MISS and in the cache / nginx-cache / cache-level1 / temp / cache file additional 0000002. This is also true with the next request until the file has on / nginx-cache / cache-level1 / cache. I+ts activity is not the same with what I've read on http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache_use_stale it said was "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". I also refer http://nginx.org/en/docs/http/ngx_http_upstream_module.html
" $upstream_cache_status

keeps the status of accessing a response cache (0.8.3). The status can be either “MISS”, “BYPASS”, “EXPIRED”, “STALE”, “UPDATING”, “REVALIDATED”, or “HIT” "

So when its status will be "UPDATING" Is there added to the cache server configuration file

upstream storage {

server 192.168.1.3:80;

server 192.168.1.4:80;

}

This is true with proxy_next_upstream.

Can you help me explain this problem, thank all

agentzh

Hello!

On Wed, Sep 9, 2015 at 10:20 AM,  <nguyennha...@gmail.com> wrote:
> When I request to cache server with cmd "curl -I
> http://192.168.1.2/cache/path/to/file"; , I received one response has
> X-Proxy-Cache are MISS, then I checked in directory / a / a, I saw one of
> the form tmp file 0000001 (this is the file that I had sent in
> $reuqest_uri).

You know that temp files are not cache files, right? Basically temp
files can contain partial data that's where nginx buffers and
accumulates the incoming data from the remote.

Are you seeing a cache file in your cache/ subdirectory?
proxy_cache_use_stale only use cache files which are *complete*
resources. It never use potentially partial data in temp files.

BTW, your configuration line "proxy_max_temp_file_size 0;" is
meaningless since you're using proxy_cache in the same location
anyway.

Regards,
-agentzh

nguyennhatkhang2704

Hi agentzh !
Thanks for your answer.
" Are you seeing a cache file in your cache/ subdirectory?"
I only see the cache file in /nginx-cache/cache-level1/

cache after the temp files disappear means it has finished, I know it !

proxy_cache_use_stale only use cache files which are *complete*
resources. It never use potentially partial data in temp files."

I think that after finishing cache (file exists in /nginx-cache/cache-level1/

cache). This time proxy_pass directive will not passed request to backend server, so when $upstream_cache_status UPDATING will appear ?
Here is what I understand about proxy_cache_use_stale:
I have two requests: the first request connect to cache server then cache server pass it to storage server and cached server will caching respond from storage server. At this time cache server will be written 1 file /nginx-cache/cache-levlevel1/temp. The second request connect to cache server, it will not pass to storage server because $upstream_cache_status is UPDATING and would not have files temp written(nginx-cache/cache-level1/temp). Same as "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" ( http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache_use_stale)

nguyennhatkhang2704

I'm try to edit proxy_cache_valid expires is smaller. Then i'm seeing +when proxy_cache_valid expires, $upstream_cache_status is EXPIRES then pass request to proxied server and save respond in to proxy cahe temp directory. During recived data from proxied server the $upstream_cache_status is UPDATING and no more other files stored in proxy cahe temp directory. When temp file download done then it will overwrite the old file in in proxy cache directory, $upstream_cache_status is HIT. I'm starting know it.