Apache 2.4.7 on Ubuntu 14.04
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I'm running Apache 2.4.7 on Ubuntu. It's a pretty standard installation using Digital Ocean's one click WordPress install.
It ran fine for months with absolutely no problem. The problem first appeared 3 days ago and at that time the server had been up for 60 days without a hiccup.
Apache is not crashing but it's just hanging. It won't respond at all. Http requests time out. The apache2 process is running however.
Top shows no load. Neither physical nor virtual memory has run out. There is nothing in the error log. There is nothing strange in the access log.
The only way to fix it is to reboot the server. "service apache2 restart" fails, "service apache2 start" fails.
Absolutely nothing has been changed on the server at all in many months. I setup the server around Feb '15. There have been exactly zero crashes (or hangs) since I setup the server in Feb '15 until 3 days ago. Since then apache has hung just about once every 24 hours. I have found no fix other than to reboot the whole system.
When I try to check out the server status (or any other URL really) I get this:
Connecting to 127.0.0.1:80... connected. HTTP request sent, awaiting response...
And it will just hang indefinitely.
Can anyone help me troubleshoot and fix this?