利用nginx做tcp负载均衡

　　当前nginx-13.1已经支持tcp,ucp,unix域套接字三种负载均衡模式（http肯定支持，这个不用说）。最近有需求需要对后端服务做负载均衡，因此考虑使用nginx来做。

1. 下载nginx,我下载的是nginx-release-1.13.1:

　　https://github.com/nginx/nginx

2. 编译,安装：

　　./auto/configure --prefix=/home/stars/support/nginx-release-1.13.1/install --with-threads --with-stream

　　make && make install

3. 编辑/home/stars/support/nginx-release-1.13.1/install/conf/nginx.conf:

　　

 #user  nobody;
 worker_processes  ;

 #error_log  logs/error.log;
 #error_log  logs/error.log  notice;
 #error_log  logs/error.log  info;

 #pid        logs/nginx.pid;

 events {
     worker_connections  ;
 }

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

     #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
     #                  '$status $body_bytes_sent "$http_referer" '
     #                  '"$http_user_agent" "$http_x_forwarded_for"';

     #access_log  logs/access.log  main;

     sendfile        on;
     #tcp_nopush     on;

     #keepalive_timeout  ;
     keepalive_timeout  ;

     #gzip  on;

     server {
         listen       ;
         server_name  localhost;

         #charset koi8-r;

         #access_log  logs/host.access.log  main;

         location / {
             root   html;
             index  index.html index.htm;
         }

         #error_page                /.html;

         # redirect server error pages to the static page /50x.html
         #
         error_page        /50x.html;
         location = /50x.html {
             root   html;
         }

         # proxy the PHP scripts to Apache listening on 127.0.0.1:
         #
         #location ~ \.php$ {
         #    proxy_pass   http://127.0.0.1;
         #}

         # pass the PHP scripts to FastCGI server listening on 127.0.0.1:
         #
         #location ~ \.php$ {
         #    root           html;
         #    fastcgi_pass   127.0.0.1:;
         #    fastcgi_index  index.php;
         #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
         #    include        fastcgi_params;
         #}

         # deny access to .htaccess files, if Apache's document root
         # concurs with nginx's one
         #
         #location ~ /\.ht {
         #    deny  all;
         #}
     }

     # another virtual host using mix of IP-, name-, and port-based configuration
     #
     #server {
     #    listen       ;
     #    listen       somename:;
     #    server_name  somename  alias  another.alias;

     #    location / {
     #        root   html;
     #        index  index.html index.htm;
     #    }
     #}

     # HTTPS server
     #
     #server {
     #    listen        ssl;
     #    server_name  localhost;

     #    ssl_certificate      cert.pem;
     #    ssl_certificate_key  cert.key;

     #    ssl_session_cache    shared:SSL:1m;
     #    ssl_session_timeout  5m;

     #    ssl_ciphers  HIGH:!aNULL:!MD5;
     #    ssl_prefer_server_ciphers  on;

     #    location / {
     #        root   html;
     #        index  index.html index.htm;
     #    }
     #}

 }

 stream{
119     upstream dds{
120         least_conn;
121         server 127.0.0.1:18890 weight=1;
122         server 127.0.0.1:17088 weight=1;
123     }
124     server{
125         listen 55055;
126         proxy_pass dds;
127     }
128 }

　　红颜色部分为新添加部分。

　　当前负载均衡算法有三类：

　　1）least_conn： 对于每个请求，nginx plus选择当前连接数最少的server来处理；

　　2）least_time： 对于每个链接,nginx pluns 通过几点来选择server的；

　　3）普通的hash算法：nginx plus选择这个server是通过user_defined 关键字，就是IP地址：$remote_addr;

4. 参数说明：

　　weight：权重

　　max_conns：最大连接数

　　max_fails：最大连接失败数

　　fail_timout：在这个时间段中进行了多少次连接的尝试失败了，那么就认为是不可达了并标记不可达