I have several nginx web servers as reverse proxy.

I found out that the active connections(including reading writing and waiting , seen from http_stub_status module) in some of the servers(not all of them) are keep growing
from 3000 to 5000, 10000 .... 10k ... 50k, and never reduce even in the late night.

at the same time , I got a more reliable number from netstat
netstat -nap | grep 80 | grep EST | wc -l
2743

the keepalive_timeout is 10 sec

the worker processes are all started at the same time

5265 nginx: master process 6-19:18:55 May19
24498 \_ nginx: worker process 59:34 19:16
24499 \_ nginx: worker process 59:34 19:16
24500 \_ nginx: worker process 59:34 19:16
24501 \_ nginx: worker process 59:34 19:16
24502 \_ nginx: cache manager pr 59:34 19:16


I've found a similar problem at:

http://markmail.org/search/?q=Upload+module+%2B+PHP+causes+active+connections+to+continually#query:Upload%20module%20%2B%20PHP%20causes%20active%20connections%20to%20continually+page:1+mid:fdgyk6v32lnvaxul+state:results

but seems not the same with me. There's also no related error in error.log

the system is

cat /etc/issue
CentOS release 5.3 (Final)
Kernel \r on an \m

uname -a
Linux 2.6.18-128.el5xen #1 SMP Wed Jan 21 11:12:42 EST 2009 x86_64 x86_64 x86_64 GNU/Linux

the nginx version:

nginx -V
nginx version: Nginx/1.0.14
built by gcc 4.1.2 20080704 (Red Hat 4.1.2-44)
TLS SNI support disabled
configure arguments: --prefix=/home/web/nginx/ --user=nobody --group=nobody
--with- http_ssl_module --with-http_sub_module --with-http_dav_module
--with-http_flv_module -- with-http_gzip_static_module
--with-http_stub_status_module --http-proxy-temp-path=/home/web/nginx/data/proxy
--http-fastcgi-temp-path=/home/web/nginx/data/fastcgi
--http-client-body-temp-path=/home/web/nginx/data/client --with-pcre=../pcre-7.9
--add-module=../ngx_http_upstream_keepalive-d7643c291ef0
--add-module=../hmux/ --add-module=../nginx-sticky-module-1.0/
--with-google_perftools_module --add-module=../nginx_upstream_check_module-660183a

the modules are:

1: for cookie sticky
nginx-sticky-module.googlecode.com
2: hmux module for resin
code.google.com/p/nginx-hmux-module/
3: upstream check module
github.com/yaoweibin/nginx_upstream_check_module
4: upstream keepalive
mdounin.ru/hg/ngx_http_upstream_keepalive/

all patches are applied to nginx src code.

nginx.conf:
===========================================

user nobody;
worker_processes 4;
worker_cpu_affinity 0001 0010 0100 1000;
google_perftools_profiles /home/web/nginx/tcmalloc/tc;

events {
worker_connections 51200;
use epoll;
epoll_events 4096;
multi_accept on;
accept_mutex off; }

http {
include mime.types;
default_type application/octet-stream;

log_format main '$remote_addr - $remote_user [$time_local] '
'$status $body_bytes_sent ';


access_log logs/access.log main;

sendfile on;
keepalive_timeout 10;

server_tokens off;

gzip on;
gzip_types text/plain text/css application/x-javascript text/xml application/json application/xml application/xml+rss text/javascript;
gzip_vary on;

server_names_hash_max_size 4096;
proxy_buffer_size 64k;
proxy_buffers 8 64k;
proxy_busy_buffers_size 64k;
client_header_buffer_size 64k;
large_client_header_buffers 4 64k;
proxy_headers_hash_max_size 1024;
proxy_headers_hash_bucket_size 128;
client_max_body_size 25m;

upstream backend{
check interval=5000 fall=3 rise=2 timeout=2000 default_down=false type=tcp;
keepalive 1024;
server server1:80;
server server2:80;
}
server {
listen 80;
server_name xxx;


location / {
proxy_pass http://backend;
}

error_page 500 502 503 504 /50x.html;

location = /50x.html {
root html;
}
}

}