怎么使用nginx进行负载均衡

四层负载均衡 vs 七层负载均衡

经常会说七层负载均衡还是四层负载均衡，其实根据iso的osi网络模型的所在层的叫法而决定的，nginx因为在使用http协议在应用层进行负载均衡的操作，所以被称为七层负载均衡。而诸如lvs在tcp层进行负载均衡操作的则被称为四层负载均衡。一般来说，有如下层的负载均衡分类：

常见软件的支持

常见的负载均衡算法

负载均衡常见有如下几种算法：

负载均衡演示实例：普通轮询

接下来使用nginx来演示一下如何进行普通轮询：

事前准备

事前在7001/7002两个端口分别启动两个服务，用于显示不同信息，为了演示方便，使用tornado做了一个镜像，通过docker容器启动时传递的参数不同用于显示服务的不同。

[root@kong ~]# docker run -d -p 7001:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "user service 1: 7001"
ddba0abd24524d270a782c3fab907f6a35c0ce514eec3159357bded09022ee57
[root@kong ~]# docker run -d -p 7002:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "user service 1: 7002"
95deadd795e19f675891bfcd44e5ea622c95615a95655d1fd346351eca707951
[root@kong ~]# 
[root@kong ~]# curl http://192.168.163.117:7001
hello, service :user service 1: 7001
[root@kong ~]# 
[root@kong ~]# curl http://192.168.163.117:7002
hello, service :user service 1: 7002
[root@kong ~]#

启动nginx

[root@kong ~]# docker run -p 9080:80 --name nginx-lb -d nginx 
9d53c7e9a45ef93e7848eb3f4e51c2652a49681e83bda6337c89a3cf2f379c74
[root@kong ~]# docker ps |grep nginx-lb
9d53c7e9a45e    nginx           "nginx -g 'daemon ..."  11 seconds ago   up 10 seconds    0.0.0.0:9080->80/tcp                         nginx-lb
[root@kong ~]#

nginx代码段

准备如下nginx代码段将其添加到nginx的/etc/nginx/conf.d/default.conf中

http {
upstream nginx_lb {
  server 192.168.163.117:7001;
  server 192.168.163.117:7002;
}
server {
  listen    80;
  server_name www.liumiao.cn 192.168.163.117;
  location / {
    proxy_pass http://nginx_lb;
  }
}

修改default.conf的方法

可以通过在容器中安装vim达到效果，也可以在本地修改然后通过docker cp传入，或者直接sed修改都可。如果在容器中安装vim，使用如下方式即可

[root@kong ~]# docker exec -it nginx-lb sh
# apt-get update
...省略
# apt-get install vim
...省略

修改前

# cat default.conf
server {
  listen    80;
  server_name localhost;
  #charset koi8-r;
  #access_log /var/log/nginx/host.access.log main;
  location / {
    root  /usr/share/nginx/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  /usr/share/nginx/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;
  #}
}
#

修改后

# cat default.conf
upstream nginx_lb {
  server 192.168.163.117:7001;
  server 192.168.163.117:7002;
}
server {
  listen    80;
  server_name www.liumiao.cn 192.168.163.117;
  #charset koi8-r;
  #access_log /var/log/nginx/host.access.log main;
  location / {
    #root  /usr/share/nginx/html;
    #index index.html index.htm;
    proxy_pass http://nginx_lb;
  }
  #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  /usr/share/nginx/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;
  #}
}
#

重启nginx容器

[root@kong ~]# docker restart nginx-lb
nginx-lb
[root@kong ~]#

确认结果

可以清晰地看到按照顺序，进行轮询：

[root@kong ~]# curl
hello, service :user service 1: 7001
[root@kong ~]# curl
hello, service :user service 1: 7002
[root@kong ~]# curl
hello, service :user service 1: 7001
[root@kong ~]# curl
hello, service :user service 1: 7002
[root@kong ~]#

负载均衡演示实例：权重轮询

而在此基础上，进行权重轮询只需要加上weight即可

修改default.conf

按照如下修改default.conf

# cp default.conf default.conf.org
# vi default.conf
# diff default.conf default.conf.org
2,3c2,3
<   server 192.168.163.117:7001 weight=100;
<   server 192.168.163.117:7002 weight=200;
---
>   server 192.168.163.117:7001;
>   server 192.168.163.117:7002;
#

重启nginx容器

[root@kong ~]# docker restart nginx-lb
nginx-lb
[root@kong ~]#

确认结果

可以看到轮询结果按照1/3和2/3的比重在进行了：

[root@kong ~]# curl
hello, service :user service 1: 7001
[root@kong ~]# curl
hello, service :user service 1: 7002
[root@kong ~]# curl
hello, service :user service 1: 7002
[root@kong ~]#

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