I have 1 single website running on 1 single Amazon EC2 instance (Linux, Medium size). Our website is based on WordPress and it has W3 Total Cache enabled

+ Page cache - except for logged-in users  
+ Object cache  
+ Browser cache

I have noticed that there is a huge difference between the number of active visitors and the number concurrent connections to our web server at 1 point of time.

At 1 point, there were only 5 active visitors but there was 100+ concurrent connections to our server (determined by netstat -plan | grep :80 | wc -l). At another point, there were 10 active visitors but there were 50 and more concurrent connections to our web server.

Can anyone give me some hints on what directions should I go about troubleshooting this issue (I call an issue since 168 concurrent connections caused our server to be down yesterday, when we were still using small EC2 instance)?

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  • If you look in the logs you'll probably see many requests coming from the same source(s). Every image, script file, and css file that is referenced on the page will come to the server as a separate request. I'm not familiar with EC2 though. What kind of tuning options do you have? – BenC Aug 16 '12 at 15:45
  • Hi, by "tuning options" I suppose you're referring to "Apache tuning"? I don't think I have any here since I'm no system administration expert. Also, could elaborate a bit more on what "logs" you're referring to here? Thanks – ericn Aug 17 '12 at 2:52

This seems normal. Each browser makes multiple requests to retrieve different parts of the webpage such as javascript, images and such. There might be multiple connections from networks behind NAT that sends traffic from the NAT IP.

You can check your apache access_log to verify if the unique IP addresses and every request to your website will be logged.

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