Nginx主主负载均衡

1. Nginx主机配置

ser www www;
worker_processes 8;
pid /usr/local/nginx/logs/nginx.pid;
worker_rlimit_nofile 51200;
events {
  user epoll;
  worker_connections 51200;
}
http {
  include mine.types;
  default_type application/octet-stream;
  server_names_hash_bucket_size 128;
  client_header_buffer_size 32k;
  large_client_header_buffers 4 32k;
  client_max_body_size 8m;
  sendfile on;
  tcp_nopush on;
  keepalive_timeout 60;
  tcp_nodelay on;
  fastcgi_connect_timeout 300;
  fastcgi_send_timeout 300;
  fastcgi_read_timeout 300;
  fastcgi_buffer_size 64k;
  fastcgi_buffers 4 64k;
  fastcgi_busy_buffer_size 128k;
  fastcgi_temp_file_write_size 128k;
  gzip on;
  gzip_min_length 1k;
  gzip_buffers 4 16k;
  gzip_http_version 1.0;
  gzip_comp_level 2;
  gzip_types text/plain application/x-javascript text/css application/xml;
  gzip_vary on;

  upstream backend {
    server 192.168.1.17:80; #web server 1
    server 192.168.1.18:80; #web server 2
  }
  server {
    listen 80;
    server_name www.bee.2.com;
    location / {
      root /var/www/html;
      index index.php index.htm index.html;
      proxy_redirect off;
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_pass http://backend;
    }
    location /nginx {
      access_log off;
      auth_basic "NginxStatus";
    }
    log_format access '$remote_addr - $remote_user [$time_local] "$request"' '$status $body_bytes_sent "$http_referer" ' '"$http_user_agent" $http_x_forwarded_for';
    access_log /data/logs/access.log access;
  }
}

2. Keepalived的实现原理
   Keepalived启用两个实例，两台Nginx主机互为备份。生成的两个VIP分别都指向目标网站，​​​比如www.bee.2.com​​。另，采用DNS轮询访问该网站。

• 第一台Keepalived配置如下：

! Configuration File for keepalived
global_defs {
  notification_email {
    bee@163.com
  }
  notification_email_from keepalived@bee.com
  smtp_server 127.0.0.1
  smtp_connect_timeout 30
  router_id LVS_DEVEL
}
vrrp_instance VI_1 {
  state MASTER
  interface eth0
  virtual_router_id 51
  priority 100
  advert_int 1
  authentication {
    auth_type PASS
    auth_pass bee.2.com
  }
  virtual_ipaddress {
    192.168.1.8  #VIP 1
  }
}
vrrp_instance VI_2 {
  state BACKUP
  interface eth0
  virtual_router_id 52
  priority 99
  advert_int 1
  authentication {
    auth_type PASS
    auth_pass bee.2.com
  }
  virtual_ipaddress{
    192.168.1.9  #VIP 2
  }
}

• 第二台Keepalived的配置如下

! Configuration File for keepalived
global_defs {
  notification_email {
    bee@163.com
  }
  notification_email_from keepalived@bee.com
  smtp_server 127.0.0.1
  smtp_connect_timeout 30
  router_id LVS_DEVEL
}
vrrp_instance VI_1 {
  state BACKUP
  interface eth0
  virtual_router_id 51
  priority 99
  advert_int 1
  authentication {
    auth_type PASS
    auth_pass bee.2.com
  }
  virtual_ipaddress {
    192.168.1.8
  }
}
vrrp_instance VI_2 {
  state MASTER
  interface eth0
  virtual_router_id 52
  priority 100
  advert_int 1
  authentication {
    auth_type PASS
    auth_pass bee.2.com
  }
  virtual_ipaddress{
    192.168.1.9
  }
}

Keepalived实现不了应用程序级别的高可用性，需要通过shell脚本实现。
脚本/root/nginx_pid.sh

#!/bin/bash
while :
do
  nginxpid=`ps -C nginx --no-header | wc -l`
  if [ $nginxpid -eq 0 ]; then
    /usr/local/nginx/sbin/nginx
    sleep 5
    if [ $nginxpid -eq 0 ]; then
      /etc/init.d/keepalived stop
    fi
  fi
  sleep 5
done

分别在两台主机上运行

nohup sh /root/nginxpid.sh &

注意，杀nginx进程（好几个）需用killall。

pgrep -l nginx  #不使用-l，则只输出pid
killall

SSL证书可考虑采用GeoTrust。