How To Use ApacheBench To Do Load Testing on an Ubuntu 13.10 VPS

Introduction

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Load testing is a good idea before any deployment. It’s nice to quickly establish a best-case scenario for a project before running more detailed tests down the road.

The ApacheBench tool (ab) can load test servers by sending an arbitrary number of concurrent requests. Although ab was designed for testing Apache installations, it can be used to benchmark any HTTP server.

In this tutorial, we will see how a Ruby interpreter with different servers performs under load. The tutorial steps assume a fresh Ubuntu 13.10 x32 image. The results were obtained from a 512 MB droplet.

Installation

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Refresh the package database.

apt-get update

Install the apache2-utils package to get access to ApacheBench.

apt-get install apache2-utils

Limited Privilege User

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Next, create the user that will manage Ruby. It’s not a good idea to run some of the commands in the next section as root.

useradd -m -d /home/test -s /bin/bash -g sudo test

What this command accomplishes:

• useradd - create a new user

• -m - create the home directory

• -d /home/test - set the user’s home directory to /home/test

• -s /bin/bash - make the user’s default shell bash (Ubuntu uses dash by default)

• -g sudo - add user to the sudo group (for running commands with sudo)

• test - the name of the new user

Set the password for the new user.

passwd test

Switch to the new user.

su test

RVM

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The Ruby Version Manager makes it easy to work with different Ruby environments. It takes care of the process of installing specific Ruby versions and isolating gemsets. It is currently installed by running a bash script from their website.

\curl -L https://get.rvm.io | bash -s stable

In order to use the rvm command, you need to first run the rvm script.

source ~/.rvm/scripts/rvm

If you want, you can put it in your .bashrc so that rvm is available any time you login as the user.

echo "source ~/.rvm/scripts/rvm" >> ~./bashrc

You can verify that the rvm script is being used by checking the head of type. It should be a function and not hashed.

type rvm | head -1

rvm is a function

Next, install Ruby 2.0.0. RVM will ask for the user’s password because it needs to install an assortment of dependencies before it can make Ruby. Since RVM builds Ruby from source, this step may take a while.

rvm install 2.0.0

Switch to the new Ruby. This might happen by default after the installation, but checking doesn’t hurt.

rvm use 2.0.0

Testing

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Now that Ruby is installed, you can create a simple site and see how many requests it can handle.

Install Sinatra. It’s a microframework/DSL for creating Ruby web applications. The --no-* flags skip the documentation.

gem install sinatra --no-rdoc --no-ri

Create the sample sinatra app which just echoes “hello world”.

cd ~
vim app.rb

# app.rb
require 'sinatra'

get '/' do
  'hello world'
end

Run the server.

ruby app.rb

With the server finally up, you can start load testing. A call to ab looks like this:

ab -n <num_requests> -c <concurrency> <addr>:<port><path>

Open another terminal and ssh into the server again. Run a test with ApacheBench. I used 1000 requests with a concurrency of 100. Don’t forget the final ‘/’ for the path.

ab -n 1000 -c 100 http://localhost:4567/

Server Software:        WEBrick/1.3.1
Server Hostname:        localhost
Server Port:            4567

Document Path:          /
Document Length:        11 bytes

Concurrency Level:      100
Time taken for tests:   3.410 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      288000 bytes
HTML transferred:       11000 bytes
Requests per second:    293.23 [#/sec] (mean)
Time per request:       341.034 [ms] (mean)
Time per request:       3.410 [ms] (mean, across all concurrent requests)
Transfer rate:          82.47 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    1   2.0      0      11
Processing:   185  332  90.3    311     578
Waiting:       28  280  83.2    267     574
Total:        193  333  89.7    311     578

Percentage of the requests served within a certain time (ms)
  50%    311
  66%    357
  75%    423
  80%    446
  90%    467
  95%    480
  98%    490
  99%    501
100%    578 (longest request)

My results converged around 300 requests/second. WEBrick is not known for its speed. Go ahead and interrupt the server with Ctrl-c.

Install Thin

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Thin is a popular ruby web server that uses Mongrel for parsing and EventMachine for non-blocking IO. Install Thin and run the server again. Sinatra should load Thin automatically and let you know (“…with backup from Thin”).

gem install thin
ruby app.rb

Now, try the load test again. It should be a bit faster this time.

Server Software:        thin
Server Hostname:        localhost
Server Port:            4567

Document Path:          /
Document Length:        11 bytes

Concurrency Level:      100
Time taken for tests:   1.339 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      244000 bytes
HTML transferred:       11000 bytes
Requests per second:    747.00 [#/sec] (mean)
Time per request:       133.870 [ms] (mean)
Time per request:       1.339 [ms] (mean, across all concurrent requests)
Transfer rate:          178.00 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    1   1.8      0       8
Processing:    55  128  19.9    132     155
Waiting:       42  116  19.7    121     144
Total:         62  129  18.5    132     156

Percentage of the requests served within a certain time (ms)
  50%    132
  66%    135
  75%    137
  80%    139
  90%    144
  95%    149
  98%    152
  99%    155
100%    156 (longest request)

At least in this case, it looks like Thin makes for a notably faster server than WEBrick at over 700 requests/second (You can try raising the total requests, but it didn’t get much higher for me).

Note: I was able to get 1000 requests/second on an Arch Linux droplet.

Conclusion

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Obviously, these results do not reflect realistic server performance. HTTP is just one piece of the puzzle. A slow templating engine and/or database will drag these numbers down significantly. Still, it gives you a quick ballpark figure for comparison.

Other performance tools you might be interested in:

• httperf
• weighttp
• httpress
• siege
• JMeter
• tourbus

<div class=“author”>Submitted by: <a href=“http://robertqualls.com”>Robert Qualls</a></div>

echo "source ~/.rvm/scripts/rvm" >> ~/.bashrc

echo "source ~/.rvm/scripts/rvm" >> ~./bashrc