Testing your site’s performance using ApacheBench

The other day we had a huge slowdown on some pages of our website, and when I investigated the cause I re-discovered a great tool for troubleshooting page-load speeds.

The problem with investigating performance problems is that it’s hard to tell if a change have any effect. Sometimes a page might look faster or slower to load depending on caching, the number of requests, CPU load, and many other factors.

I needed a tool to simulate the load and return me a nicely formatted report. At this point I remembered about ApacheBench (ab).

I opened up my Ubuntu box and installed it. The installation is quite simple:

$ sudo apt-get update; sudo apt-get install apache2-utils;

After installing it I immediately tried to test the speed of my endpoint:

$ ab -n 100 -c1 -A admin:secret https://localhost:3000/api/test/page

Explanation:
-n <number> number of requests to generate

-c <number> number of threads to spawn

-A <login:password> basic http authentication

The end result is a nicely formatted report:

This is ApacheBench, Version 2.3 <$Revision: 1528965 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking localhost (be patient).....done


Server Software:        WEBrick/1.3.1
Server Hostname:        localhost
Server Port:            3002
SSL/TLS Protocol:       TLSv1.2,DHE-RSA-AES256-GCM-SHA384,2048,256

Document Path:          /api/v2/makes/Volkswagen/models/Golf
Document Length:        5909 bytes

Concurrency Level:      1
Time taken for tests:   19.100 seconds
Complete requests:      100
Failed requests:        0
Total transferred:      654500 bytes
HTML transferred:       590900 bytes
Requests per second:    5.24 [#/sec] (mean)
Time per request:       191.003 [ms] (mean)
Time per request:       191.003 [ms] (mean, across all concurrent requests)
Transfer rate:          33.46 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        5    7   1.7      6      11
Processing:    92  184  92.7    196     976
Waiting:       92  184  92.7    195     975
Total:         97  191  93.0    201     985

Percentage of the requests served within a certain time (ms)
  50%    201
  66%    210
  75%    218
  80%    220
  90%    233
  95%    250
  98%    275
  99%    985
 100%    985 (longest request)

With such a powerful tool, fixing the issue was a piece of cake!

Originally published at underthehood.carwow.co.uk on July 24, 2015.

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