Apache fails with seg fault

I found appache fault in logs /var/log/apache2/error.log:

[timestamp] [mpm_event:notice] [pid 20056:tid 140176783820672] AH00493: SIGUSR1 received. Doing graceful restart
[timestamp] [core:notice] [pid 20056] AH00060: seg fault or similar nasty error detected in the parent process

Websites are not working with 502 Bad Gateway.

On my side the issue was with logrotate software and the fault in setting:

$ sudo nano /etc/logrotate.d/apache2

In this file you should change apache2 reload to apache2 restart !

That's it!