Knowing whether it is actually up.
THE COMPLICATION
A monitoring service checking your domain reaches the CDN. If the CDN serves a cached copy or an error page, the result may not reflect your server's state.
Your site can be down while monitoring reports it up, and the reverse.
WHAT TO MONITOR
The public domain, which is what visitors experience The origin directly, using the server hostname, which tells you whether our server is healthy
Both, ideally.
WHAT CLOUDFLARE SHOWS
Analytics for requests, cached versus origin, and errors.
A rise in 52x errors means Cloudflare is having trouble reaching us.
WHAT WE SHOW
cPanel > Metrics > Errors and Resource Usage reflect what actually reached us.
WHEN THEY DISAGREE
The public site failing while our logs are quiet means the request never arrived. Look at the CDN.
Our logs showing errors while the public site appears fine means cached copies are masking a problem.
FOR A BUSINESS SITE
Monitoring that alerts you before a customer does is worth the small cost.