What could be the reason for the website crash?

Question

MySQL

Site on Codeigniter
Ubuntu nginx + php-fpm, mysql
Yesterday I changed nginx settings (added a new host) and the site crashed at that time. I thought that I did something wrong, rolled back the settings, reloaded nginx, but there is no result.
When you enter the site, it takes a very long time to load and everything, restarted mysql, everything was ok.
after 10 minutes, the site crashed again, restarted nginx mysql again and started working
at night, the site crashed, but rose by itself
in the nginx mysql logs is empty

Answer 1

So what fell, nginx, mysql or both?
Logging slow muscle requests to the rescue.

Answer 2

at the time of the "blunt" site, look in the mysql processlist, what's going on there?

Answer 3

Have you changed the .haccess file?

Answer 4

With such introductory 100,500 problem options. Localize the problem. Check separately php, separately mysql and separately nginx.
1. Create a simple php script without connecting to the database, run it through the console. If there are problems after launch, then the problems are in php.
2. Connect via console to mysql. Write a request, do it. Brakes? If so, then the problem is in mysql.
3. Open a static html page. Opening slowly? I screwed up with ngnix.
If you do not follow these steps, then you will now be advised anything you want. From enabling caching to moving to apache, python and postgr.

Answer 5

My permanent base fell off on the Ocean :)