# How to cap server load?

**URL:** <https://www.ruby-forum.com/t/how-to-cap-server-load/229595>\
**Category:** NGINX\
**Created:** [January 5, 2013, 5:15pm UTC](https://www.ruby-forum.com/t/how-to-cap-server-load/229595 "2013-01-05T17:15:58Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![KT\_Walrus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/a87d85/32.png) [@KT\_Walrus](https://www.ruby-forum.com/u/KT_Walrus)\
**Post date:** [January 5, 2013, 5:15pm UTC](https://www.ruby-forum.com/t/how-to-cap-server-load/229595/1 "2013-01-05T17:15:58Z")

</div>

I really want to ensure that my web servers are not overloaded.

Can I do this with nginx?

That is, is there a variable I could test to decide whether nginx should  
send the request to the local PHP backend or to forward the request to  
other nginx servers in the server farm, based on the load of the PHP  
backend? Maybe a variable that contains how many concurrent requests to  
nginx are waiting for a response?

---

<div class="post-metadata">

**Author:** ![KT\_Walrus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/a87d85/32.png) [@KT\_Walrus](https://www.ruby-forum.com/u/KT_Walrus)\
**Post date:** [January 5, 2013, 7:21pm UTC](https://www.ruby-forum.com/t/how-to-cap-server-load/229595/2 "2013-01-05T19:21:34Z")

</div>

You need to test the response time of a sample php script. Mark the  
back end as down if it fails the response time threshold a certain  
number of times. After you back off, it should recover health if your  
algorithm is working. Remember, the database is likely to be the  
ultimate performance issue with php performance.

* * *

Stefan C.  
[https://www.scaleengine.com/](https://www.scaleengine.com/)

---

<div class="post-metadata">

**Author:** ![KT\_Walrus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/a87d85/32.png) [@KT\_Walrus](https://www.ruby-forum.com/u/KT_Walrus)\
**Post date:** [January 5, 2013, 7:32pm UTC](https://www.ruby-forum.com/t/how-to-cap-server-load/229595/3 "2013-01-05T19:32:40Z")

</div>

Good idea of measuring actual response time, but I’m just looking to for  
a more crude limit of setting a maximum number of concurrent requests  
for the localhost server before requests are “bounced” to another  
backend.

But, do you know how to do the “response time” limit within NGINX? Or,  
do I need to do this test with scripts outside NGINX and have all load  
balancers that send requests to this backend do health checks (again  
outside NGINX) and edit configuration file and reload NGINX?

If so, I might as well put HAProxy in front of NGINX which can do what I  
want.

I was looking for a simple way within NGINX to see how many concurrent  
requests there are for the localhost backend.

Just exploring my options…

Kevin

---

<div class="post-metadata">

**Author:** ![KT\_Walrus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/a87d85/32.png) [@KT\_Walrus](https://www.ruby-forum.com/u/KT_Walrus)\
**Post date:** [January 6, 2013, 12:35am UTC](https://www.ruby-forum.com/t/how-to-cap-server-load/229595/4 "2013-01-06T00:35:50Z")

</div>

There are a number of ways; varnish does this with its director back  
end definitions, gdnsd also lets you use health checks to manage  
server pools, and you have mentioned haproxy. The reason I mentioned  
database at the beginning, is that you ultimately have to “protect”  
the database with your system, by identifying which requests are  
hurting you most frequently, and looking for creative ways to reduce  
that pressure on the database. Unless you can provide relief and  
backend pool management with a protection system, you can make things  
worse with larger webservers and more backends.