Chris Page – Software Engineer

I’ve been knee deep in performance and scalability for some time now, and have used and learned of many useful tools and techniques to help out. One of my favorite command line tools for seeing how well a single Apache server is churning out pages in development comes stock on Ubuntu, and Mac OS X: Apache Benchmark.

A simple performance test against the homepage of one of my client site’s using AB at the command line:

ab -t5 -n100 http://www.teamgzfs.com/

The results:

This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking www.teamgzfs.com (be patient)
Finished 664 requests

Server Software:        Apache/2.2.8
Server Hostname:        www.teamgzfs.com
Server Port:            80

Document Path:          /
Document Length:        306 bytes

Concurrency Level:      100
Time taken for tests:   5.054 seconds
Complete requests:      664
Failed requests:        0
Write errors:           0
Total transferred:      465003 bytes
HTML transferred:       205326 bytes
Requests per second:    131.38 [#/sec] (mean)
Time per request:       761.143 [ms] (mean)
Time per request:       7.611 [ms] (mean, across all concurrent requests)
Transfer rate:          89.85 [Kbytes/sec] received

Connection Times (ms)
min  mean[+/-sd] median   max
Connect:       38   78  48.7     64     994
Processing:   114  540 226.2    493    1690
Waiting:      114  531 205.6    493    1485
Total:        191  618 236.0    558    1808

Percentage of the requests served within a certain time (ms)
50%    558
66%    587
75%    598
80%    617
90%    845
95%   1163
98%   1402
99%   1746
100%   1808 (longest request)

There is quite a bit of useful information here that can help you tune your code and server. It’s important to note however, that when working on a larger site, that expects quite a bit more traffic, you might want to investigate some more thorough solutions outside of just a single machine and ab. It is, however, a nice starting point into useful information.

One rather funny pitfall you can run into however, is if the host you are sending requests to is smartly secured – these types of tests become a bit useless, as they may have security settings to limit or delay requests – providing you with timeouts and/or inaccurate information. Best to run these types of things in a semi-developmental mode with those types of security settings turned down, and rely on bigger guns or fleets of boxes and scripts to hit a production secure site.

In addition to hitting just a landing page, you can use AB to send COOKIE or POST data too! This is very useful if you want to see how pages perform but need credentials to get in first. This is a little trickier to do using the -c, -T, -p, and -v flags. I noticed there are under-useful resources online to figuring it out with AB, so it would seem worthwhile to write it – as it took me some trickery to figuring it out as well:

Sending POST data to a login form:

First we create a file that contains our URL encoded post data. Note, AB expects the values to be URL encoded, but not the equal (=) or ampersands (&).

post_data.txt

username=foo%40bar.com&password=foobar

Capturing a cookie:

Here, we use the verbosity (-v) flag so we can see the response headers that come back — many sites will send back a cookie once authenticated, we’ll want to capture that cookie here. Though, some sites will not require it, I demonstrate it for the sake of example:

ab -v4 -n1 -T 'application/x-www-form-urlencoded' -p post_data.txt http://www.foobar.com/login

The returned response header will fly by quick, you’re looking for something like the following:

Set-cookie somesession=somerandomsessiondata...;

The session data may come back encrypted, unencrypted, a serialization, or just a number. That varies by site. The point here is you have a key/value pair for the cookie. All you need is the part up to the semi-colon ( not including the semi-colon ). Copy that “key=val” string, and use it when hitting other pages on the site you are testing, ie:

Using a cookie to test a page that requires a cookie:

ab -t10 -n100 -c 'somessession=somerandomsessiondata' http://www.foobar.com/login_required_page

This can become a lot of fun once you get the hang of it. Now you have the know how, go enjoy creating an arsenal of these scripts and start performance tuning your sites – or script hacking your favorite social network ( or obnoxious Blizzard clan website hahaha… drum roll for D3 – 2010? Please???! ).