How to run speed test.
the image to use
The image you should probably use is: cf_219kb.png
cf_219kb.png is an image that won't be compressed by Jetpack Wordpress. So, uploading that image to both Jetpack and CloudFront CDN will result in the same image being downloaded.
curl-format.txt is how to run the speed test.
Here is a shell script of how the speed test is run:
the curl command
speedtest() {
curl -w "@curl-format.txt" -o tmp -s $@
}
Please note that you do NOT want to -o /dev/null, as this will make curl
will cleverly skip the data transfer (i.e. download) phase. Which will throw
off your speed test measurement. So it is important to have -o tmp to
actually download the file.
the measurement
the very first curl you should copy-paste into your notes. This curl is very interesting to measure because the 1st curl is always the slowest. This is usually the biggest variance between the CDNs. The first curl is an indicator of how fast the CDN loads for 1st-time visitors.
the 2nd measurement is doing at least 10 subsequent curls, and taking the average. This measures how well a CDN caches content for multiple page visitors.
The script
Installation:
The script uses the pycurl module. To install it run:
$ pip3 install pycurl
If the installation fails you may need to install these dependencies:
- libssl-dev
- libcurl4-openssl-dev On Linux:
$ sudo apt-get install libssl-dev libcurl4-openssl-dev
Testing:
To run it just run:
$python3 script.py < url >
Example:
$ python3 script.py 'https://d3va53q3li7xt1.cloudfront.net/wp-content/uploads/2021/05/shoeb-1024x576.png'
Output:
10 requests done. Average:
time_namelookup: 0.004422
time_connect: 0.014404
time_appconnect: 0.036274900000000006
time_pretransfer: 0.03636879999999999
time_redirect: 0.0
time_starttransfer: 0.049656500000000006
time_total: 0.0496897
The other files
cf.png is 703KB.
wp.png is 329KB.
Jetpack Wordpress compressed cf.png down to wp.png, which is why Jetpack won the initial speed test.