md5 fastcgi cache collisions

Ian M. Evans ianevans at
Sat Sep 22 20:39:47 UTC 2012

Was looking at my error log and noticed a whole bunch of errors like this:

2012/09/22 15:52:26 [crit] 641#0: *4896016 cache file
"/var/lib/nginx/fastcgicache/3/21/32d5a44032aadeeed2b1d027314ba213" has
md5 collision, client: x.x.x.x, server:, request: "GET
/cr/denzelwashington/ HTTP/1.1", host: ""

My fastcgi cache is setup as follows:

fastcgi_cache_path /var/lib/nginx/fastcgicache levels=1:2
keys_zone=MYCACHE:5m inactive=2h max_size=1g loader_files=1000
map $http_cookie $no_cache { default 0; ~SESS 1; }
fastcgi_cache_key "$scheme$request_method$host$request_uri";
add_header X-My-Cache $upstream_cache_status;

/cr is actually a php file called like this in the nginx.conf from a
thread years ago:

location ~ ^/cr(/.*$|$) {
rewrite ^/cr(/.*$|$) /$1.php?mypath=$2 last;

Site's working fine...just wondering what's causing all the collisions.


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