Apache+Passenger - Apache running; but not responding to requests

Background

I'm running a Ruby on Rails application that has to serve a lot of static files as well.

My setup currently is:

Debian Linux Lenny 5.0 Apache 2.2.9 Passenger 2.2.10

The problem

Everything runs fine. I see apache process spinning up, passenger instances get created and everything works fast and snappy.

Then, after some time Apache does not respond to requests any more. Clients do get a connection and are "waiting for a response", but none comes.

I cannot manually reproduce this problem. Sometimes it occurs a few hours after a restart, other times it takes a f开发者_JAVA百科ew days to happen. Here's what I found:

Apache process are up; Passenger is there, but it does not have any instances spun up (probably because instances die after a period of inactivity)

No error messages or problems in /var/log/syslog, /var/log/messages, not in apache's access and errors logs, not in my Rails production log. Nothing.

When I stop and start apache everything is back to normal.

Does any one have any clues what's happening here? And how it can be resolved?

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Due to an enormous load on static files we decided to host static files on separate server (later Amazon S3+CloudFront) for performance reasons.

My current guess is that Apache couldn't cope with the large number of requests on static files and also doing Passenger. The current setup is Nginx+Unicorn for the Rails application and S3+CloudFront for static files.