Why is apache crashing?
We have troubles with the server down in the last 3-4 days. Opening the graph, we see the change in the CPU/Traffic load which double from previous 7-8% to 13-14%. But that's relatively small and shouldn't cause the server down.
I'm running Apache, PHP-FPM, MariaDB. And when server down, Apache is off. I have to ssh and restart Apache again.
FYI: to have a better performance, I've just upgraded PHP from 7.0 to 7.3. The Ubuntu version is still 16.04 LTS.
I'd agree that a slight increase in CPU usage is probably not the problem here.
From the symptoms you are describing, my guess is that this may be due to either your Linode running out of memory, or an Apache configuration issue.
I'd suggest the following:
Monitor your memory usage. If your server is running out of memory, it may shut down processes unexpectedly. Something like
free -mis a good place to start, though the linked guide above has a few more helpful commands.
Run the Apache2 optimizer. If Apache is shutting down unexpectedly, then it may be a configuration issue. Tuning its configuration should result in better performance.
Review the Apache log: If apache is being shutdown, you should be able to locate an error message that provides so more helpful information. If this occurs again, I'd suggest taking a look at the last output of /var/log/apache2/error.log to see if it sheds more light on why this is occurring.