One of the most targeted goals when optimizing a website for page load speed is to get a good score on Google PageSpeed Insights test. But it is not enough to work hard on optimization, achieve a good score and go to sleep. It is essential to periodically monitor score changes as a website evolves and undergoes changes over time which affect this metric.

Here’s a little script that will allow you to automatically track Google PageSpeed Insight score and be alerted if it falls below a custom value.

Psi tool

The script is based on a small but very useful Javascript tool called psi developed by Addy Osmani, so you need first to install it using the Npm package manager of Node.js:

$ npm install --save psi

Once installed, this program shows on the command line the same information we can get through the official Google web application:

The desktop-pagespeed-score-watchdog.sh script

This is a small Bash script that filters the information provided by the psi command and dumps the result to a log file that records score changes over time. It can also be processed by a monitoring system which generates some kind of alert when the website’s score falls below a certain value.

#! /bin/bash 
 
scoreLimitDesktop="90"
website="www.daniloaz.com"
error=0 
 
log () 
{ 
        logFileName=`echo $0 | egrep -o "[^\/]+$"` 
        logStatusFile=$logFileName.status 
        logFile=$logFileName.log 
 
        echo "$1|$2" > /var/log/$logStatusFile 
        echo `date +%Y-%m-%d\ %H:%M:%S`"|$1|$2" >> /var/log/$logFile 
} 
 
if [ ! -f /usr/bin/psi ];then 
    echo "Error: /usr/bin/psi command is not installed." 
    exit 1 
fi 
 
scoreDesktop=`/usr/bin/psi --strategy=desktop "$website" | grep 'Speed:' | awk '{print $2}'` 
 
if [ $scoreDesktop -lt $scoreLimitDesktop ];then 
    msg="ERROR: the desktop PageSpeed score of $website fell to ${scoreDesktop}/100."  
    echo $msg 
    log 2 "$msg"
    exit 1 
else 
    msg="OK: the desktop PageSpeed score is equal to or greater than the limit: ${scoreDesktop}/100." 
    echo $msg 
    log 0 "$msg" 
    exit 0 
fi

This example script gets the score for desktop, but could equally get it for mobile by just changing the –strategy=desktop parameter by –strategy=mobile.

The script can be executed as often as you want by adding a cron task:

# Monitor every 15 minutes the www.daniloaz.com site score in Google PageSpeed Insights
0,15,30,45      *       *       *       *       /bin/bash /usr/local/scripts/desktop-pagespeed-score-watchdog.sh

Finally, this is the look of the log that periodically records the evolution of PageSpeed score:

$ cat desktop-pagespeed-score-watchdog.sh.log
2017-05-26 12:00:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 12:15:03|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 12:30:03|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 90/100. 
2017-05-26 12:45:03|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 90/100. 
2017-05-26 13:00:03|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 13:15:03|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 13:30:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 13:45:03|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 14:00:03|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 14:15:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 14:30:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 14:45:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 15:00:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 15:15:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 15:30:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100. 
2017-05-26 15:45:04|0|OK: the desktop PageSpeed score is equal to or greater than the limit: 91/100.
2017-05-26 16:00:04|2|ERROR: the desktop PageSpeed score of www.daniloaz.com fell to 89/100.
2017-05-26 16:15:03|2|ERROR: the desktop PageSpeed score of www.daniloaz.com fell to 89/100.