Nginx hang and do not respond with large number of network connection in FIN_WAIT state

[Peter Booth]

The important question here is not the connections in FIN_WAIT. It’s “why do you have so many sockets in ESTABLISHED state?”

First thing to do is to run 
netstat -ant | grep tcp and see where these connections are to.

Do you have a configuration that is causing an endless loop of requests?

Sent from my iPhone

> On Jan 9, 2019, at 9:57 PM, Anoop Alias <anoopalias01 at gmail.com> wrote:
> 
> Hi,
> 
> Have had a really strange issue on a Nginx server configured as a reverse proxy wherein the server stops responding when the network connections in ESTABLISHED state and FIN_WAIT state in very high compared to normal working 
> 
> If you see the below network graph, at around 00:30 hours there is a big spike in network connections in FIN_WAIT state, to around 12000 from the normal value of  ~20
> 
> https://i.imgur.com/wb6VMWo.png
> 
> At this state, Nginx stops responding fully and does not work even after a full restart of the service.
> 
> Switching off Nginx and bring Apache service to the frontend (removing the reverse proxy) fix this and the connections drop
> 
> Nginx config & build setting
> ##################################
>  nginx -V
> nginx version: nginx/1.15.8
> built by gcc 4.8.5 20150623 (Red Hat 4.8.5-36) (GCC) 
> built with LibreSSL 2.8.3
> TLS SNI support enabled
> configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --modules-path=/etc/nginx/modules --with-pcre=./pcre-8.42 --with-pcre-jit --with-zlib=./zlib-1.2.11 --with-openssl=./libressl-2.8.3 --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error_log --http-log-path=/var/log/nginx/access_log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --http-client-body-temp-path=/dev/shm/client_temp --http-proxy-temp-path=/dev/shm/proxy_temp --http-fastcgi-temp-path=/dev/shm/fastcgi_temp --http-uwsgi-temp-path=/dev/shm/uwsgi_temp --http-scgi-temp-path=/dev/shm/scgi_temp --user=nobody --group=nobody --with-http_ssl_module --with-http_realip_module --with-http_addition_module --with-http_sub_module --with-http_dav_module --with-http_flv_module --with-http_mp4_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_random_index_module --with-http_secure_link_module --with-http_stub_status_module --with-http_auth_request_module --with-file-aio --with-threads --with-stream --with-stream_ssl_module --with-http_slice_module --with-compat --with-http_v2_module --add-dynamic-module=incubator-pagespeed-ngx-1.13.35.2-stable --add-dynamic-module=/usr/local/rvm/gems/ruby-2.5.3/gems/passenger-6.0.0/src/nginx_module --add-dynamic-module=ngx_brotli --add-dynamic-module=echo-nginx-module-0.61 --add-dynamic-module=headers-more-nginx-module-0.32 --add-dynamic-module=ngx_http_redis-0.3.8 --add-dynamic-module=redis2-nginx-module --add-dynamic-module=srcache-nginx-module-0.31 --add-dynamic-module=ngx_devel_kit-0.3.0 --add-dynamic-module=set-misc-nginx-module-0.31 --add-dynamic-module=ngx_http_geoip2_module --add-dynamic-module=testcookie-nginx-module --add-dynamic-module=ModSecurity-nginx --with-cc-opt='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' --with-ld-opt=-Wl,-E
> 
> #####################################
> # worker_processes  auto;  #Set to auto for a powerful server
> worker_processes  1;
> worker_rlimit_nofile 69152;
> worker_shutdown_timeout 10s;
> # worker_cpu_affinity auto;
> timer_resolution 1s;
> thread_pool iopool threads=32 max_queue=65536;
> pcre_jit on;
> pid        /var/run/nginx.pid;
> error_log /var/log/nginx/error_log;
> 
> #Load Dynamic Modules
> include /etc/nginx/modules.d/*.load;
> 
> 
> events {
> worker_connections  20480;
> use epoll;
> multi_accept on;
> accept_mutex off;
> }
> 
> lingering_close off;
> limit_req zone=FLOODVHOST burst=200;
> limit_req zone=FLOODPROTECT burst=200;
> limit_conn PERSERVER 60;
> client_header_timeout  5s;
> client_body_timeout 5s;
> send_timeout 5s;
> keepalive_timeout 0;
> http2_idle_timeout 20s;
> http2_recv_timeout 20s;
> 
> 
> aio threads=iopool;
> aio_write on;
> directio 64m;
> output_buffers 2 512k;
> 
> tcp_nodelay on;
> 
> types_hash_max_size 4096;
> server_tokens off;
> client_max_body_size 2048m;
> reset_timedout_connection on;
> 
> #Proxy
> proxy_read_timeout 300;
> proxy_send_timeout 300;
> proxy_connect_timeout 30s;
> 
> #FastCGI
> fastcgi_read_timeout 300;
> fastcgi_send_timeout 300;
> fastcgi_connect_timeout 30s;
> 
> #Proxy Buffer
> proxy_buffering on;
> proxy_buffer_size          128k;
> proxy_buffers              8 128k;
> proxy_busy_buffers_size    256k;
> 
> #FastCGI Buffer
> fastcgi_buffer_size          128k;
> fastcgi_buffers              8 128k;
> fastcgi_busy_buffers_size    256k;
> 
> server_names_hash_max_size 2097152;
> server_names_hash_bucket_size 128;
> ######################################################
> 
> 
> 
> -- 
> Anoop P Alias 
> 
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