md5 fastcgi cache collisions

Ian Evans ianevans at
Tue Sep 25 03:07:14 UTC 2012

On 24/09/2012 8:27 PM, Maxim Dounin wrote:

> Is the file reported is the same in all errors?

Yes in the sense that the "cr" in /cr/nameofperson is an extensionless 
php file.

> Most likely it's a corrupted cache file.  Looking into the cache
> file should be enough to see if it's indeed corrupted.

just did a 'more cachefilename' and it looks fine but the log reported a 

> Intresting question is to find out how the file was corrupted.
> This may be either something "normal" like filesystem corruption
> after power failure, or something in nginx.  The later case might
> need investigation.
> If you just want to get rid of the messages you may try to remove
> the cache file, it should fix things.  Normal nginx behaviour is
> to replace such currupted cache files with new responses, but it
> looks like it doesn't work in your case, likely because responses
> aren't cacheable.

I went to one of the pages. The error log reported an md5 collision. I 
removed the file, cleared my cache and requested it again. Another md5 
collision in the error log, but again the file looked fine.

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