Debugging Nginx Cache Misses: Hitting high number of MISS despite high proxy valid

[Quintin Par]

That’s the tricky part. These MISSes are intermittent. Whenever I run curl
I get HITs but I end up seeing a lot of MISS in the logs.



How do I log these MiSSes with the reason? I want to know what headers
ended up bypassing the cache.



Here’s my caching config



            proxy_pass http://127.0.0.1:8000;

                proxy_set_header X-Real-IP  $remote_addr;

                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

                proxy_set_header X-Forwarded-Proto https;

                proxy_set_header X-Forwarded-Port 443;



                # If logged in, don't cache.

                if ($http_cookie ~*
"comment_author_|wordpress_(?!test_cookie)|wp-postpass_" ) {

                  set $do_not_cache 1;

                }

                proxy_cache_key "$scheme://$host$request_uri$do_not_cache";

                proxy_cache staticfilecache;

                add_header Cache-Control public;

                proxy_cache_valid       200 120d;

                proxy_hide_header "Set-Cookie";

                proxy_ignore_headers  "Set-Cookie";

                proxy_ignore_headers  "Cache-Control";

                proxy_hide_header "Cache-Control";

                proxy_pass_header X-Accel-Expires;



                proxy_set_header Accept-Encoding "";

                proxy_ignore_headers Expires;

                add_header X-Cache-Status $upstream_cache_status;

                proxy_cache_use_stale   timeout;

                proxy_cache_bypass $arg_nocache $do_not_cache;
- Quintin


On Sat, May 12, 2018 at 10:29 AM Lucas Rolff <lucas at lucasrolff.com> wrote:

> It can be as simple as doing a curl to your “origin” url (the one you
> proxy_pass to) for the files you see that gets a lot of MISS’s – if there’s
> odd headers such as cookies etc, then you’ll most likely experience a bad
> cache if your nginx is configured to not ignore those headers.
>
>
>
> *From: *nginx <nginx-bounces at nginx.org> on behalf of Quintin Par <
> quintinpar at gmail.com>
> *Reply-To: *"nginx at nginx.org" <nginx at nginx.org>
> *Date: *Saturday, 12 May 2018 at 18.26
> *To: *"nginx at nginx.org" <nginx at nginx.org>
> *Subject: *Debugging Nginx Cache Misses: Hitting high number of MISS
> despite high proxy valid
>
>
>
> [image:
> https://mailtrack.io/trace/mail/86a613eb1ce46a4e7fa6f9eb96989cddae639800.png?u=74734]
>
> My proxy cache path is set to a very high size
>
>
>
> proxy_cache_path  /var/lib/nginx/cache  levels=1:2
>  keys_zone=staticfilecache:180m  max_size=700m;
>
> and the size used is only
>
>
>
> sudo du -sh *
>
> 14M cache
>
> 4.0K    proxy
>
> Proxy cache valid is set to
>
>
>
> proxy_cache_valid 200 120d;
>
> I track HIT and MISS via
>
>
>
> add_header X-Cache-Status $upstream_cache_status;
>
> Despite these settings I am seeing a lot of MISSes. And this is for pages
> I intentionally ran a cache warmer an hour ago.
>
>
>
> How do I debug why these MISSes are happening? How do I find out if the
> miss was due to eviction, expiration, some rogue header etc? Does Nginx
> provide commands for this?
>
>
>
> - Quintin
> _______________________________________________
> nginx mailing list
> nginx at nginx.org
> http://mailman.nginx.org/mailman/listinfo/nginx
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