Proxy Errors with unicorn and apache2 reverse proxy

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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:

[Tue May 22 22:56:31 2012] [error] [client 146.52.xx.xx] proxy: Error reading from remote server returned by /photos/upload, referer:
[Tue May 22 22:58:49 2012] [error] (103)Software caused connection abort: proxy: pass request body failed to (
[Tue May 22 22:58:49 2012] [error] proxy: pass request body failed to ( 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:

chdir: /apps/pics/prod/current
log: log/thin.log
port: 9001
environment: production
pid: tmp/pids/
servers: 4
onebyone: true
wait: 60
timeout: 600
max_persistent_conns: 512

Important is the timeout of 10minutes here, to complete large uploads of pictures. For reference, this is my apache vhost conf:

DocumentRoot /apps/pics/prod/current/public


ProxyRequests Off
ProxyBadHeader Ignore

ProxyPass / balancer://unicornservers/
ProxyPassReverse / balancer://unicornservers/
ProxyPreserveHost on
ProxyPass /photos/large !
ProxyPass /photos/original !

ProxyPass /photos/thumb !

Order deny,allow
Allow from all

AllowEncodedSlashes on

SetEnv force-proxy-request-1.0 1
SetEnv proxy-nokeepalive 1
SetEnv proxy-initial-not-pooled 1

I found the last environment settings in some post about apache proxy problems.

Maybe someone with the same problem can take this as a starting point to fix this kind of problem with unicorn. I switch back to thin, which is fine.