If they have a good enough DDOS'er, they can take down your gunz server by flooding it especially if you have no DDOS protection.
This isn't the case here, it's exploiting apache's keepalive system w/ threads, not DoS attacking, it's sending http requests over and over and never completing them fully. If you want to call that "DoSing", fine, but it's far from DDOSing and easily fixable.
I had the same issue on an unrelated to gunz project, for the record, and it was solved by disabling the keepalive timeout.
Also, this:
Code:
[Fri Aug 12 08:54:05 2011] [warn] Server ran out of threads to serve requests. Consider raising the ThreadsPerChild setting
means it's running out of threads to serve requests. Do you not seem to understand that it is running out of threads due to keepalive holding them for 15 seconds each http request? By disabling the thread keepalive, you instantly free up connections when the transaction is over. This means that the max amount of threads (see: MaxKeepAliveRequests defaulting to 100, Each connection is a thread) is being taken up, and apache will refuse all new connections because of that.