If you find this in your Apache error logs:
```apacheconf
[error] (103)Software caused connection abort: proxy: pass request body failed to 127.0.0.1:50000 (127.0.0.1)
[error] proxy: pass request body failed to 127.0.0.1:50000 (127.0.0.1) from 1.1.1.1.1 ()
```
Make sure you have read the [Apache manuals](http://httpd.apache.org/docs/current/mod/mod_proxy.html#proxypass)
Also read the "BalancerMember parameters" and "Balancer parameters" sections, e.g. maxattempts.
Relevant settings to test with your application and configuration might be:
```apacheconf
SetEnv proxy-sendchunked 1
SetEnv proxy-sendchunks 1
SetEnv downgrade-1.0 1
SetEnv proxy-sendcl 1
```
It all depends on where Apache is sending the requests and what features the backend supports.
If you're using Unicorn with e.g. Rails then read:
http://unicorn.bogomips.org/DESIGN.html
http://unicorn.bogomips.org/PHILOSOPHY.html
Unicorn doesn't support nokeepalive for a reason, so maybe you should switch to [Rainbows!](http://rainbows.rubyforge.org/), thin and/or nginx.
If changing the server you use is not an option, you could try:
```apacheconf
SetEnv force-proxy-request-1.0 1
SetEnv proxy-nokeepalive 1
```
or e.g.:
```apacheconf
BalancerMember xxx keepalive=Off maxattempts=2
```
If you have issues with large file uploads and unicorn, [this might help](http://rubyforge.org/pipermail/mongrel-unicorn/2011-September/001195.html).