$connections_waiting ever increasing

[nemster]

TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --conf-path=/etc/nginx/nginx.conf
--sbin-path=/usr/bin/nginx --pid-path=/run/nginx.pid
--lock-path=/run/lock/nginx.lock --user=http --group=http
--http-log-path=/var/log/nginx/access.log --error-log-path=stderr
--http-client-body-temp-path=/var/lib/nginx/client-body
--http-proxy-temp-path=/var/lib/nginx/proxy
--http-fastcgi-temp-path=/var/lib/nginx/fastcgi
--http-scgi-temp-path=/var/lib/nginx/scgi
--http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-mail
--with-mail_ssl_module --with-pcre-jit --with-file-aio
--with-http_dav_module --with-http_gunzip_module
--with-http_gzip_static_module --with-http_realip_module
--with-http_v2_module --with-http_ssl_module --with-http_stub_status_module
--with-http_addition_module --with-http_degradation_module
--with-http_flv_module --with-http_mp4_module --with-http_secure_link_module
--with-http_sub_module --with-http_geoip_module --with-stream --with-threads
--add-module=../naxsi/naxsi_src --add-module=../headers-more-nginx-module
--add-module=../nginx-ct --add-module=../lua-nginx-module

relevant config details:

worker_processes  auto;
worker_rlimit_nofile 40000;

events {
    worker_connections  40000;
    use epoll;
    multi_accept on;
}

http {
    include       mime.types;
    default_type  application/octet-stream;
   sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    #keepalive_timeout 5;
    types_hash_max_size 2048;
    server_tokens off;

location = /status {
           # Turn on stats
           stub_status on;
           access_log   off;
}

.... upstream servers and stuff

}

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,271269,271275#msg-271275