I usually used thin as app-server for Rails in combination with Apache2 as webserver. I tried using unicorn instead, because I read a lot of interesting articles about it. Unfortunatly, now I got a lot of error messages like that when uploading files:
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[Tue May 22 22:56:31 2012] [error] [client 146.52.xx.xx] proxy: Error reading from remote server returned by /photos/upload, referer: http://pics.stefanwienert.de/
[Tue May 22 22:58:49 2012] [error] (103)Software caused connection abort: proxy: pass request body failed to 127.0.0.1:9001 (127.0.0.1)
[Tue May 22 22:58:49 2012] [error] proxy: pass request body failed to 127.0.0.1:9001 (127.0.0.1) from 146.52.xx.xx ()
[Tue May 22 22:59:01 2012] [error] proxy: client 146.52.xx.xx given Content-Length did not match number of body bytes read
Switching back to thin and the following config works fine: