网站不能处理超过 50 个并发访问者，这是什么问题？

如何解决网站不能处理超过 50 个并发访问者，这是什么问题？

当超过 50 名访问者同时到达时，我的网站在发送电子邮件后会变慢。然后它变得非常慢，有时会给出 502 Bad Gateway。我试图更改 PHP 和 NGINX 上的一些设置 - 这并没有解决它。 为了能够看到发生了什么，我在服务器 (Netdata) 上安装了一个工具，它在“高峰时间”提供实时信息。我还使用了一个工具对 50 个并发访问者进行负载测试（flood.io） 看起来，当测试开始时，CPU 使用率立即增长到 100%。内存差不多了，还没用完，还有80Mb左右可用内存，交换文件还没用，我觉得挺好的。

唯一的日志文件备注是：

警告：[pool www] 似乎很忙（您可能需要增加 pm.start_servers 或 pm.min/max_spare_servers），产生 8 个孩子， 有 0 个空闲，总共有 12 个孩子警告：[pool www] 服务器 达到 pm.max_children 设置（15），考虑提高它[错误] 26813#26813: *114871 connect() 到 unix:/var/run/php/php7.4-fpm.sock 连接到时失败（11：资源暂时不可用） 上游，上游：“fastcgi://unix:/var/run/php/php7.4-fpm.sock:”

我尝试调整但无法进行更多调整，所以我希望这个问题可以让您了解现在该怎么做。我预计访问者必须超过 50 人。为了测试，我将该站点复制到了它自己的专用 VPS，因此没有什么会减慢它的速度。我该怎么做才能让它接受更多的访客？任何帮助将不胜感激！

我正在测试的网址是 https://test.parkeer24.nl - Ubuntu 18.04 (LTS) 上的设置是 Drupal 8、1 GB RAM、25 GB SSD、1 个 CPU，并且大多数设置都是默认设置。>

NGINX 1.14.0 nginx.conf：

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

events {
    worker_connections 1024;
}

http {
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    types_hash_max_size 2048;
    server_tokens off;
    client_body_buffer_size 10K;
    client_header_buffer_size 1k;
    client_max_body_size 8m;
    large_client_header_buffers 2 1k;
    fastcgi_buffers 16 16k;
    fastcgi_buffer_size 32k;
    client_body_timeout 12;
    client_header_timeout 12;
    keepalive_timeout 15;
    send_timeout 10;
    include /etc/nginx/mime.types;
    default_type application/octet-stream;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3,ref: POODLE
    ssl_prefer_server_ciphers on;
    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;
    gzip on;
    gzip_comp_level  2;
    gzip_min_length  1000;
    gzip_proxied     expired no-cache no-store private auth;
    gzip_types       text/plain application/x-javascript text/xml text/css application/xml;
    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;
}

PHP 7.4 php.ini:

[PHP]
engine = On
short_open_tag = Off
precision = 14
output_buffering = 4096
zlib.output_compression = Off
implicit_flush = Off
serialize_precision = -1
disable_functions = pcntl_alarm,pcntl_fork,pcntl_waitpid,pcntl_wait,pcntl_wifexited,pcntl_wifstopped,pcntl_wifsignaled,pcntl_wifcontinued,pcntl_wexitstatus,pcntl_wtermsig,pcntl_wstopsig,pcntl_signal,pcntl_signal_get_handler,pcntl_signal_dispatch,pcntl_get_last_error,pcntl_strerror,pcntl_sigprocmask,pcntl_sigwaitinfo,pcntl_sigtimedwait,pcntl_exec,pcntl_getpriority,pcntl_setpriority,pcntl_async_signals,pcntl_unshare,zend.enable_gc = On
zend.exception_ignore_args = On
expose_php = Off
max_execution_time = 30
max_input_time = 60
memory_limit = 128M
error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT
display_errors = Off
display_startup_errors = Off
log_errors = On
log_errors_max_len = 1024
ignore_repeated_errors = Off
ignore_repeated_source = Off
report_memleaks = On
variables_order = "GPCS"
request_order = "GP"
register_argc_argv = Off
auto_globals_jit = On
post_max_size = 8M
default_mimetype = "text/html"
default_charset = "UTF-8"
enable_dl = Off
file_uploads = On
upload_max_filesize = 2M
max_file_uploads = 20
allow_url_fopen = On
allow_url_include = Off
default_socket_timeout = 60
[CLI Server]
cli_server.color = On
[mail function]
SMTP = localhost
smtp_port = 25
mail.add_x_header = Off
[ODBC]
odbc.allow_persistent = On
odbc.check_persistent = On
odbc.max_persistent = -1
odbc.max_links = -1
odbc.defaultlrl = 4096
odbc.defaultbinmode = 1
[MySQLi]
mysqli.max_persistent = -1
mysqli.allow_persistent = On
mysqli.max_links = -1
mysqli.default_port = 3306
mysqli.default_socket =
mysqli.default_host =
mysqli.default_user =
mysqli.default_pw =
mysqli.reconnect = Off
[mysqlnd]
mysqlnd.collect_statistics = On
mysqlnd.collect_memory_statistics = Off
[bcmath]
bcmath.scale = 0
[Session]
session.save_handler = files
session.use_strict_mode = 0
session.use_cookies = 1
session.use_only_cookies = 1
session.name = PHPSESSID
session.auto_start = 0
session.cookie_lifetime = 0
session.cookie_path = /
session.cookie_domain =
session.cookie_httponly =
session.cookie_samesite =
session.serialize_handler = php
session.gc_probability = 0
session.gc_divisor = 1000
session.gc_maxlifetime = 1440
session.referer_check =
session.cache_limiter = nocache
session.cache_expire = 180
session.use_trans_sid = 0
session.sid_length = 26
session.trans_sid_tags = "a=href,area=href,frame=src,form="
session.sid_bits_per_character = 5
[Assertion]
zend.assertions = -1
[Tidy]
tidy.clean_output = Off
[soap]
soap.wsdl_cache_enabled=1
soap.wsdl_cache_dir="/tmp"
soap.wsdl_cache_ttl=86400
soap.wsdl_cache_limit = 5
[ldap]
ldap.max_links = -1

PHP www.conf:

[www]
user = www-data
group = www-data
listen = /run/php/php7.4-fpm.sock
listen.owner = www-data
listen.group = www-data
pm = dynamic
pm.max_children = 15
pm.start_servers = 3
pm.min_spare_servers = 3
pm.max_spare_servers = 6