How to send a notification about a site crash?

Question

System administration

There is a site, it falls periodically, then the 500th error, then another. Are there any simple solutions, perhaps a ready-made cron that will compare the text and send an email in case of an error

Answer 1

https://www.icinga.org/
https://www.nagios.org/
The first is a fork of the second.

Answer 2

monitoring the availability of the site from different countries of the world and changing the hoster due to the low availability
of www.host-tracker.com
montastic.com