http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache_convert_head
W dniu 04.03.2021 o 15:03, Señor J Onion pisze:
> I use nginx as a forward proxy, with content caching.
>
> My app first performs a HEAD request to a Google Cloud Storage object. Then
> it may perform a GET request to the same object.
>
> The HEAD request (which comes first) causes a cache MISS. The content body
> length returned to the client is 0 (which is obviously correct).
>
> However, I think that the actual object is still included in the body from
> the upstream response. The reason I believe why the object gets added to the
> HEAD response from the upstream service (GCS) is for two reasons:
>
> a) When I subsequently do the GET request, I don't get a cache MISS (even
> though this is my first GET request to that object), but a cache REVALIDATED.
> The response from the upstream service is just a 304 with no body saying the
> cached object is still valid ($upstream_header_time and
> $upstream_response_time are identical == 0.421, which would then be correct
> if the cached object is still valid).
> So - this seems like the initial HEAD request cached the response also as a
> GET request with the body of the object that seemed to have been in the HEAD
> request
>
> b) Also, when I do the initial HEAD request, I can see that the
> $upstream_header_time==0.832, and the $upstream_response_time==2.459 ... If
> it's a HEAD request there really shouldn't be a body, so I would expect both
> $upstream_header_time and $upstream_response_time to be identical. However
> the 1.5sec time difference shows me that there is something in the body (even
> though when the request returns to the client it all seems correct again in
> terms of that the actual response.body.length is indeed 0.)
>
> So - the way this is working is messing with my app and HTTP analytics. I
> believe this to be behaving incorrectly.
>
>
> I don't know where the "error" lies. If it is a Google Cloud Storage bug that
> it passes along the object in the body of the HEAD request, or whether the
> issue lies with nginx, or with my configuration, or whether it is with the
> content caching part of nginx?
> Or perhaps it is behaving exactly as it should, and there is something about
> the HEAD/GET requests in combination with caching that I am not understanding.
>
> Any help to shed light on this strange behaviour would be greatly appreciated.
>
>
> My server block config is as follows:
>
> proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=image_cache:10m
> inactive=60d use_temp_path=off;
>
> server {
> listen 3128;
>
> location / {
> proxy_cache image_cache;
>
> proxy_cache_revalidate on;
>
> proxy_cache_lock on;
> proxy_cache_lock_timeout 5s;
>
> proxy_ignore_headers Cache-Control;
> proxy_cache_valid 200 60d;
>
> add_header X-Cache-Status $upstream_cache_status;
>
> resolver 8.8.8.8 ipv6=off;
> proxy_pass http://$http_host$uri$is_args$args;
> }
> }
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