SIMPLE LOAD TESTING WITH APACHEBENCH (AB)

Load testing. Everyone talks about it but how many of you actually do it?

Some will complain it is too difficult to setup and get started (see JMeter). Over the next few posts I'll discuss a few easy options to get started with load testing.

Today we'll look at ApacheBench

ab is a tool for benchmarking your Apache Hypertext Transfer Protocol (HTTP) server. It is designed to give you an impression of how your current Apache installation performs. This especially shows you how many requests per second your Apache installation is capable of serving.

ApacheBench comes as part of the httpd package so if you already have Apache installed you probably have access to ab (on Windows try ab.exe).

The command is simple:

ab -k -n 5000 -c 60 -H "Accept-Encoding: gzip,deflate" http://www.thesiteyouwanttotest.com/


ab - main command
-k - sends KeepAlive header which more closely mimics browser request
-n - number of requests to make
-c - concurrency - how many requests to make at a time
-H - custom header - more closely mimic real requests

WARNING: Be careful! You are load testing an environment. It is easy to overwhelm a server if not setup correctly. You don't want to run this against your production site!

Running the command it'll spin up, test and dump some output in your terminal:

Benchmarking www.thesiteyouwanttotest.com (be patient).....done

Server Software:        nginx/1.10.1
Server Hostname:        www.thesiteyouwanttotest.com
Server Port:            80

Document Path:          /
Document Length:        24170 bytes

Concurrency Level:      5
Time taken for tests:   6.247 seconds
Complete requests:      100
Failed requests:        0
Total transferred:      2440600 bytes
HTML transferred:       2417000 bytes
Requests per second:    16.01 [#/sec] (mean)
Time per request:       312.353 [ms] (mean)
Time per request:       62.471 [ms] (mean, across all concurrent requests)
Transfer rate:          381.52 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:       72   82   5.8     81     110
Processing:   163  208 160.0    183    1775
Waiting:       82  103  22.3     95     200
Total:        245  290 159.8    266    1853

Percentage of the requests served within a certain time (ms)
  50%    266
  66%    279
  75%    287
  80%    292
  90%    316
  95%    330
  98%    363
  99%   1853
 100%   1853 (longest request)

This tells you all sorts of useful stuff:

* requests per second
* connection times
* how long those connections took

Scribble these #s down. Adjust the concurrency and number of requests and run it again.

Rinse and repeat until either your server falls over :) or you reach the goals you need.

Be aware all you are really testing is the server. You aren't emulating real users hitting the site. But it is easy to run and gives you some useful numbers.

At work we ran this against three environments: stage, ci and a sandbox and compared the data to see if any particular environment was slower than the other.

You can visually do this with a little gnuplot magic...

Modify your command and add the -g attribute:

ab -k -n 5000 -c 60 -g /home/jim/stage.tsv -H "Accept-Encoding: gzip,deflate" https://www.thesiteyouwanttotest.com/

This will output a file Gnuplot can render by using a simple script:

plot.p (for gnuplot)

#output as png image  
set terminal png

#save file to "test-output.png"  
set output "test-output.png"

#graph title  
set title "- ab -n 3000 -c 30"

#nicer aspect ratio for image size  
set size 1,0.7

# y-axis grid  
set grid y

#x-axis label  
set xlabel "request"

#y-axis label  
set ylabel "response time (ms)"

plot "stage.tsv" using 9 smooth sbezier with lines title "Stage", \  
 "ci.tsv" using 9 smooth sbezier with lines title "CI", \  
 "sandbox.tsv" using 9 smooth sbezier with lines title "Sandbox", \

Run gnuplot plot.p and you should get something like this:

gnuplot Screenshot

This allows you to easily compare each environment.

Next post we will checkout Locust.

Published on Friday, June 10 2016     Tags: testing tools

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Jim is a Senior Applications Engineer working at Red Hat. He slso likes motorcycles and keeping his quadcopter out of trees.