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I have nginx 1.4.3 running on a Ubuntu 12.04 machine. I have nginx set up to cache pages (they are database-driven but stay fairly static). I'm using MySQL and PHP-FPM.

However, I found that I would intermittently get blank pages cached. There were no errors of any kind, and as soon as I delete the appropriate file from /var/cache/nginx the page would come back.

After some investigation, I have found the issue is that if a HEAD request is received, nginx caches a blank response as the full response for that URL. So HEAD /example stores a blank file in the cache file for the /example page, and a subsequent GET /example returns a blank page. (I seem to get HEAD requests regularly from various search engines and bots.)

Here is the relevant site config:

location ~ \.php$ { try_files $uri =404; fastcgi_cache one; fastcgi_cache_key $scheme$host$request_uri; fastcgi_cache_valid 200 5m; fastcgi_cache_valid 301 302 304 12h; include /etc/nginx/fastcgi_params; fastcgi_pass 127.0.0.1:9000; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME /srv/www/mysite/public$fastcgi_script_name; fastcgi_param HTTPS off; }

Is this a known bug in nginx? I haven't been able to find any information on this though various searches.

Is there a workaround? There is no way to prevent caching HEAD requests according to this.

I thought maybe there is some 'request method' variable that could be added to fastcgi_cache_key, so that HEAD and GET requests are cached separately. But I cannot find anything.

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2 Answers 2

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Yes, the variable is $request_method and that's what you will want to add to fastcgi_cache_key. This will cause GET and HEAD requests to be cached separately.

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  • Thanks, looks like this has solved the issue! Do you think this the best method? Seems like there would be a reason why $request_method is not there by default (i.e. it's not listed in any guides or official nginx docs). Commented Jul 15, 2014 at 16:55
  • Not including this by default makes little sense, so I suspect it's a bug or simple oversight. Commented Jul 15, 2014 at 16:59
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I believe you'll want to add the http method to fastcgi_cache_key or possibly only include GET in fastcgi_cache_methods.

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