We recently had a situation where we had a client site that was
built in Umbraco perform very
poorly. I was asked to take a look, and the first thing I did was
to use the
umbdebugshowtrace=true query string to see what controls or
XSLT were performing badly. To my surprise, everything seemed
normal, the the pages were generated within 200ms.
So I opened up Charles
Web Proxy, and watched a few requests. I then noticed that the
image requests were taking AGES when we were using ImageGen.
Digging a bit deeper, I noticed that on the server, every time a
request was made for an image that used ImageGen, the CPU would
spike to 100% for a few seconds then drop. Strange.
I logged on to the server, and found the cached
directory thinking that the cache files weren't being written due
to a permission problem. Explorer waited. and waited. and crashed!
So I jumped on to our.umbraco.org and found this post about a bug
in ImageGen. It seems that the cache files weren't being deleted or
reused, so we had millions of files written to the
cached directory!
I jumped to a command prompt, ran 'rd /s cached', waited 45
minutes (!), updated the DLL and ASHX files from the
patch available here, and everything seems to be back to normal
with CPU load well below 10%.
