ApacheBench, or ab, is a small benchmark utility that comes with Apache. It's a really simple HTTP load generating tool, ideal for a simple WordPress load & speed test. How fast does your WordPress site respond? How many HTTP requests per second can your server handle? These are questions on which ab can shed some light. Here is how to load test WordPress with ApacheBench.
This especially shows you how many requests per second your Apache installation is capable of serving. Making it a perfect tool to test your WordPress hosting. Apache Bench, or ab, is available in apache2-utils, that you can easily install using apt install apache2-utils on Ubuntu.
Suppose you want to see how fast your website can handle 100 requests, with a maximum of 10 requests running concurrently. For this you use Apache Bench, or ab:
ab -n 100 -c 10 http://www.example.com/
This'll generate the following output:
Concurrency Level: 10
Time taken for tests: 2.219 seconds
Complete requests: 100
Failed requests: 0
Total transferred: 1261400 bytes
HTML transferred: 1225500 bytes
Requests per second: 45.07 [#/sec] (mean)
Time per request: 221.897 [ms] (mean)
Time per request: 22.190 [ms] (mean, across all concurrent requests)
Transfer rate: 555.14 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 9 14 5.3 13 48
Processing: 157 201 47.5 189 364
Waiting: 142 186 47.4 174 353
Total: 170 215 49.2 203 383
Percentage of the requests served within a certain time (ms)
50% 203
66% 208
75% 212
80% 214
90% 261
95% 369
98% 382
99% 383
100% 383 (longest request)
As you can see, this is very useful information. The benchmarked WordPress site returned requests at 45.07 requests per second, the fastest was 170 ms, the slowest 383 ms.
Using ApacheBench, or ab, you can easily benchmark your WordPress website with various PHP versions and configuration settings.
Benchmarking various PHP versions
Using ApacheBench, I benchmarked various PHP versions. The tested PHP versions are 5.5.30, 5.6.19 and 7.0.4, with and without Wincache, and the results are somewhat surprising, as you can see for yourself:
| PHP version | Requests per second (#/sec) | Fastest (ms) | Slowest (ms) |
|---|---|---|---|
| 7.0.4 & Wincache | 45.07 | 170 | 383 |
| 7.0.4 | 46.34 | 163 | 370 |
| 5.6.19 & Wincache | 48.63 | 149 | 390 |
| 5.6.19 | 49.85 | 143 | 400 |
| 5.5.30 & Wincache | 38.16 | 151 | 546 |
| 5.5.30 | 54.79 | 129 | 403 |
Not only does PHP 5.5.30 handle the most requests per second, it's even the fastest in this test.
All benchmark tests were performed on a shared web server running Windows Server 2012 R2 and IIS 8.5. Every time I made sure the application pool was active.
Because of the server being a shared hosting web server, there may have been load peaks during testing interfering with the results - but not that I have noticed.