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 ~]#
