How to troubleshoot a 503 error?

Question

PHP

Hello everybody! I sometimes get a 503 error on the server, google says that the problem may be in the freezing of php scripts / database / system. However, I'm not sure what exactly is causing this.
In what logs can you find information about it? costs nginx on reverse proxy and site on apache

Answer 1

https://developer.mozilla.org/ru/docs/Web/HTTP/Sta...
503, as a rule, means that the server/servers to which the request should be redirected do not exist.
If you get this response from nginx (look at the logs), then your site on Apache is failing helchecks or in some other way is not available to nginx.
If you are getting this response from an apache site, there may be something in the code that is waiting for a response from a remote server and is generating a 503 error for the same reason.

Answer 2

In what logs can you find information about it?

503 error is written to you by the web server
This means that you can find it in the logs of the web server