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

[Friscia, Michael]

I'm not sure if this will help, but I ignore/hide a lot, this is in my config


proxy_ignore_headers X-Accel-Expires Expires Cache-Control Set-Cookie;
proxy_hide_header X-Accel-Expires;
proxy_hide_header Pragma;
proxy_hide_header Server;
proxy_hide_header Request-Context;
proxy_hide_header X-Powered-By;
proxy_hide_header X-AspNet-Version;
proxy_hide_header X-AspNetMvc-Version;


I have not experienced the problem you mention, I just thought I would offer my 
config.


___________________________________________

Michael Friscia

Office of Communications

Yale School of Medicine

(203) 737-7932 – office

(203) 931-5381 – mobile

http://web.yale.edu<http://web.yale.edu/>


________________________________
From: nginx <nginx-boun...@nginx.org> on behalf of Quintin Par 
<quintin...@gmail.com>
Sent: Saturday, May 12, 2018 1:32 PM
To: nginx@nginx.org
Subject: Re: Debugging Nginx Cache Misses: Hitting high number of MISS despite 
high proxy valid



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<https://urldefense.proofpoint.com/v2/url?u=http-3A__127.0.0.1-3A8000&d=DwMFaQ&c=cjytLXgP8ixuoHflwc-poQ&r=wvXEDjvtDPcv7AlldT5UvDx32KXBEM6um_lS023SJrs&m=F-qGMOyS74uE8JM-dOLmNH92bQ1xQ-7Rj1d6k-_WST4&s=NHvlb1WColNwTWBF36P1whJdu5iWHK9_50IDHugaEdQ&e=>;

                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 
<lu...@lucasrolff.com<mailto:lu...@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-boun...@nginx.org<mailto:nginx-boun...@nginx.org>> on behalf 
of Quintin Par <quintin...@gmail.com<mailto:quintin...@gmail.com>>
Reply-To: "nginx@nginx.org<mailto:nginx@nginx.org>" 
<nginx@nginx.org<mailto:nginx@nginx.org>>
Date: Saturday, 12 May 2018 at 18.26
To: "nginx@nginx.org<mailto:nginx@nginx.org>" 
<nginx@nginx.org<mailto:nginx@nginx.org>>
Subject: Debugging Nginx Cache Misses: Hitting high number of MISS despite high 
proxy valid



[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

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