我有一台运行 LEMP 堆栈的服务器，托管各种网站。夜间，所有站点都被关闭，并显示消息“502 bad gateway”。我跟踪了错误流，得出结论是 php7.4-fpm 是问题所在。我需要帮助来找出如何解决下面的错误。
\n注意：夜间，系统未进行任何更新或更改
\n\xe2\x97\x8f php7.4-fpm.service - The PHP 7.4 FastCGI Process Manager\n Loaded: loaded (/lib/systemd/system/php7.4-fpm.service; enabled; vendor preset: enabled)\n Active: failed (Result: exit-code) since Tue 2021-07-27 09:35:38 CEST; 7s ago\n Docs: man:php-fpm7.4(8)\n Process: 1561620 ExecStart=/usr/sbin/php-fpm7.4 --nodaemonize --fpm-config /etc/php/7.4/fpm/php-fpm.conf (code=exited, status=78)\n Process: 1561621 ExecStopPost=/usr/lib/php/php-fpm-socket-helper remove /run/php/php-fpm.sock /etc/php/7.4/fpm/pool.d/www.conf 74 (code=exited, status=0/SUCCESS)\n Main PID: 1561620 (code=exited, status=78)\n\nJul 27 09:35:38 Ubuntu-2010-groovy-64-minimal systemd[1]: Starting The PHP 7.4 FastCGI Process Manager...\nJul 27 09:35:38 Ubuntu-2010-groovy-64-minimal php-fpm7.4[1561620]: [27-Jul-2021 09:35:38] ERROR: …