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Poor load balancer performance on rackspace and centos

October 19, 2011 04:10PM
I am load testing different options for load balancing, and am getting poor results from Nginx, haproxy, and varnish. I have one 4GB instance at Rackspace, hitting 4x1GB app servers.

I'm hitting a url called "/slow" which deliberately waits 500ms before responding. If I hit an application server directly it can handle a connection rate of 1600-1800 per second.

If I hit the Nginx load balancer, it can only handle about 2000 connections. I was hoping for something closer to 4x1600 = 6000. Below is the command I'm using to test it. This is run in parallel on 40 256 MB instances. I'm deliberately setting num_call to 1, because I want to see connection performance. Any higher than this and I start to get a lot of errors.

httperf --server --port 1555 --uri /slow --rate 50 --num-call 1 --num-conn 100 --timeout 5

Here is my nginx config: https://gist.github.com/1299501

So, here's the weird thing, no matter whether I use nginx, haproxy, or varnish, I get roughly the same results. However, I tested Rackspace's new cloud balancers, and they get much better performance (doing fine at 7000/s). Since nginx and the others are all running on an instance I set up, and the rackspace balancer isn't, I'm guessing there's something about the system that is wrong. I'd rather use a balancer I control, so I can add caching, gzip, ssl, and other stuff to it.

How can I find out what the bottleneck is? Is there anything I should tweak on the system to get performance to be better? Do I need more than 4GB of ram? (Ram usage is not high during the test). Any other random ideas?

Thank you for your help!
Subject Author Posted

Poor load balancer performance on rackspace and centos

seanhess October 19, 2011 04:10PM

Re: Poor load balancer performance on rackspace and centos

mwilbanks October 19, 2011 05:20PM

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