webpage timeouts

webpages timing out

[DCDebaron]

Hello Everyone,

One month ago I setup my first dedicated server and setup Apache on CENTOS6. (Apache/2.2.15) The site was working fine until the server system detected an attack (SYN Flood) and would put my server in mitigation to vacuum the bad traffic. My problem is ever since their first mitigation my web pages either time out, or after server reloads will bring up a page (non-cached as there is some logging on) but not bring up all the images. The site is forum that uses php/mysql (kind of like vbulletin or phpbb) but even the index.html page takes forever or times out.

The server support investigated during said the mitigation works fine, the traffic even at its peak is not causing high % usage, and that they 'believe it's your webserver application because when I run a 'telnet 123.45.678.999 80' it takes a long time to respond.' The tested this during a period the server was not under attack.

When the response time issue first occurred support told me it was because of my cloudlflare DNS connection (later they admitted that wasn't the problem). So I changed to another DNS host but the problem still exists.

Wen I plug the IP address into the browser the response is bad or gets timeouts. When I #time wget on the IP address and the alias, it can timeout 4 or 5 times then finish with 4 or 5 minute response time. But when I ping the IP address and alias from my windows command line, the ping returns fine.

Having not changed any configuration except for the names servers, can someone point me in a direction to what I might investigate to determine the issue?

Thanks in advance!

[phranque]

use nslookup to test your DNS.
use ping to test your connection to the hostname.
use traceroute to check all the hops between you and the web server.

most modern browsers have web developer tools or plugins available that will show a waterfall chart.
this might show problems requesting specific resources.

[DCDebaron]

nslookup returned fine, no issues.

Did DSN lookup and performance, all 4 nameservers <9ms.

Ping returns fine on IP address and alias

traceroute looks fine, all hops <36ms to final destination. one timeout on hop 5.

Used firefox firebug app for waterfall chart. Accessing the simple GET example.com/index.html got 3 aborts after waiting around 25 sec for a 10kb page. Other times GET example.com/index.html was successful between 35-50 sec then loads for 9kb and 1kb gifs aborted after 23 sec.

time wget -O /dev/null example.com still timing out several times.

[phranque]

welcome to WebmasterWorld, DCDebaron!


are those .gif requests internally rewritten to a script or are they straight filesystem requests?

[DCDebaron]

Thanks for the welcome! :)

Its a straight html request via IMG SRC.

Just to go further I changed the content of index.html to just be a 'hello world' page and in firefox sometimes it loaded after 35-50 seconds and other times it aborted after 10. Never came up in Chrome.