I’m not sure why, but there seems to be something wrong with the way this mod stores/reads its values from memcached servers. As long as the time between a read and a store is long enough, everything goes fine.

That’s why I made a script to download the images (jpeg) at fast speed (over localhost on the server). What did I see?

iterate over a list of DIFFERENT images: everything fine
iterate over a list of SAME images: MIME-type of the images not correct
(after the second iteration, the MIME-type was wrong)

I wrote the value to a logfile, and then changed the extension to see if my
explorer could open the image. But NO. Looking in this so called image,
the data seemed to be incorrect (no JFIF header for example). At other moments, the header was correct, but only a part of the image was stored.

Does this have something to do with the maximum file size of every object?
(I thought the mod doesn’t store the values, if they higher than this?)
That could explain why the data is truncated.

I also disabled UDP, with no affect. I even changed the number of threads in memcached to 1 (I thought that one apache thread was already reading, while the other was still writing), but it does not make a difference (apart from the performance).

P.S. IIPImage also uses memcached, and doesn’t have this problem.
(see http://iipimage.sourceforge.net/blog/)

Any idea?

thanks in advance!

I’ll study the memcache apache module this weekend but the previous week I taken a look and It’s just a line on the code, very clean indeed.

Thanks for the comment

I’ve had a look at mod_memcache_cache’s sources and googlecode pages, and can’t find where to configure the strategy for creating the memcache key.

I left a comment on the googlecode page (http://code.google.com/p/modmemcachecache/wiki/Configure) which I’ll re-iterate here:

-START-
Please make it a function of the request URI and the Accepts header (perhaps also per-method, e.g. only cache a response when GET is used).

So,

memcached key = md5(URI + Accepts) memcached value = response entity body (XML or JSON representation, for example)

This function will generate different keys for different response types (e.g. XML or JSON).
-END-

Perhaps you found the solution? I guess I have to install it and play around to deduce the answer.

Thanks,
Juan

I’ll add and fix what you are saying. But I have to say that this server config is not trivial thus “only” sysadmins should do this.

Bye