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  1;

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

#pid        logs/nginx.pid;


events {
    worker_connections  1024;
}


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  0;
    keepalive_timeout  65;

    #gzip  on;

    server {
        listen       12345;
        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

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

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

        # proxy the PHP scripts to Apache listening on 127.0.0.1:80
        #
        #location ~ .php$ {
        #    proxy_pass   http://127.0.0.1;
        #}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        #location ~ .php$ {
        #    root           html;
        #    fastcgi_pass   127.0.0.1:9000;
        #    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       8000;
    #    listen       somename:8080;
    #    server_name  somename  alias  another.alias;

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


    # HTTPS server
    #
    #server {
    #    listen       443 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