How To Use ApacheBench To Do Load Testing on an Ubuntu 13.10 VPS
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.
Refresh the package database.
Install the apache2-utils package to get access to ApacheBench.
apt-get install apache2-utils
Limited Privilege User
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.
Switch to the new user.
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.
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
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.
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.
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.
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: