My web site will slow down after an e-mailing, when more than 50 visitors arrive at the same time. Then it gets very slow and sometimes gives a 502 Bad Gateway. I tried to change some settings on PHP and NGINX - this didn't solve it. To be able to see what's happening I installed a tool on the server (Netdata) which gives real time information during 'rush hour'. Also I used a tool to do load testing with 50 concurrent visitors (flood.io) It appears that when testing starts, CPU usage immediately grows to 100%. Memory is almost, but not used fully, there is about 80Mb available memory left and the swap file is not used yet, which I think is good.
The only log file remarks are:
WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 8 children, there are 0 idle, and 12 total children WARNING: [pool www] server reached pm.max_children setting (15), consider raising it [error] 26813#26813: *114871 connect() to unix:/var/run/php/php7.4-fpm.sock failed (11: Resource temporarily unavailable) while connecting to upstream, upstream: "fastcgi://unix:/var/run/php/php7.4-fpm.sock:"
I tried to tune but couldn't make more of it, so I hope this question brings an insight in what to do now. I would expect that more visitors than 50 must be possible. For testing, I copied the site to it's own dedicated VPS, so nothing is slowing it down. What could I do to have it accept some more visitors? Any help would be very much appreciated!
The url on which I'm testing is https://test.parkeer24.nl - the setup is Drupal 8 on Ubuntu 18.04 (LTS), 1 GB RAM, 25 GB SSD, 1 CPU and most of the settings are default.
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
