Ncache is a caching module for nginx, similar to varnish. I just installed it using my modified nginx debian build script, and it was a little tough to get going. I kept getting this error:
2009/02/28 23:57:49 [emerg] 5579#0: ncache_index_fd < 0 2009/02/28 23:57:49 [emerg] 5579#0: ncache_http_proxy_shm_hash_init error
I poked around the code for a little bit, and found this:
ncache_index_fd = open( NGX_PREFIX"/logs/ncache_index",O_RDWR);
The problem is that they are using NGX_PREFIX, which isn't configured with the debian build script. It defaults to /usr/local/nginx. As a temporary workaround, I created /usr/local/nginx/logs/ and chowned to www-data. That fixed the problem.
Another small issue I ran into was the shell script to create the cache directories, but thankfully someone contributed a solution.
I'll probably fork this and make lots of changes to learn more about caching and nginx modules. I've added a wiki page about it here.
Unfortunately I still had problems getting this to work. :-(