• Registered: 2009-07-28
  • Posts: 335

Topic: Nginx : accept() failed (24: Too many open files) DDOS Protection

This solutions is application to cpnginx and danginx  plugins and bare nginx server configurations.
Edit the file   /etc/sysctl.conf  and increase the openfile limits. Add the following line,

fs.file-max = 700000

Edit  /etc/security/limits.conf  and add the following  lines,

nobody       soft    nofile  100000
nobody       hard    nofile  500000

Now apply the sysctl configuration using the following command .

# sysctl -p

Now edit the  /usr/local/nginx/conf/nginx.conf  file  and add the following line.

worker_rlimit_nofile 50000;

Now  stop nginx  server and restart.

Syslint Technologies | 24x7 Server Management | Outsourced Support | Software Development - (0091) 471-3273-211
  • Registered: 2009-07-28
  • Posts: 335

Re: Nginx : accept() failed (24: Too many open files) DDOS Protection

This configuration is for hightraffic servers and DDOS  issue facing servers.

Syslint Technologies | 24x7 Server Management | Outsourced Support | Software Development - (0091) 471-3273-211
  • Registered: 2009-07-28
  • Posts: 335

Re: Nginx : accept() failed (24: Too many open files) DDOS Protection

You can do the following too to protect ddso,

1)  Add the following sysctl parameters,
---------------
net.ipv4.tcp_syncookies = 1
# source validation / reversed path
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
kernel.pid_max = 65536
net.ipv4.ip_local_port_range = 9000 65000
--------------

2) Use the  RateLimit module ,   http://wiki.nginx.org/HttpLimitZoneModule   It must be placed inside http block
-----------------
limit_zone slimits $binary_remote_addr 10m;
limit_conn slimits 10;
------------------

Syslint Technologies | 24x7 Server Management | Outsourced Support | Software Development - (0091) 471-3273-211
  • Registered: 2009-07-28
  • Posts: 335

Re: Nginx : accept() failed (24: Too many open files) DDOS Protection

Some time adding the following line one second line in the  script /etc/init.d/nginx  will fix this issue

  ulimit -n 65535

Syslint Technologies | 24x7 Server Management | Outsourced Support | Software Development - (0091) 471-3273-211
  • Registered: 2009-07-28
  • Posts: 335

Re: Nginx : accept() failed (24: Too many open files) DDOS Protection

You can also use the following too,
----------------
limit_req_zone $binary_remote_addr zone=slimitss:10m rate=1r/s;
limit_req zone=slimitss  burst=10;

Syslint Technologies | 24x7 Server Management | Outsourced Support | Software Development - (0091) 471-3273-211