四層負載均衡 vs 七層負載均衡
經常會說七層負載均衡還是四層負載均衡，其實根據iso的osi網絡模型的所在層的叫法而決定的，nginx因為在使用http協議在應用層進行負載均衡的操作，所以被稱為七層負載均衡。而諸如lvs在tcp層進行負載均衡操作的則被稱為四層負載均衡。一般來說，有如下層的負載均衡分類：
常見軟件的支持
常見的負載均衡算法
負載均衡常見有如下幾種算法：
負載均衡演示實例：普通輪詢
接下來使用nginx來演示一下如何進行普通輪詢：
事前準備
事前在7001/7002兩個端口分別啟動兩個服務，用于顯示不同信息，為了演示方便，使用tornado做了一個鏡像，通過docker容器啟動時傳遞的參數不同用于顯示服務的不同。
[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?~]#
啟動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代碼段
準備如下nginx代碼段將其添加到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
可以通過在容器中安裝vim達到效果，也可以在本地修改然后通過docker cp傳入，或者直接sed修改都可。如果在容器中安裝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; ??#} } #
重啟nginx容器
[root@kong?~]#?docker?restart?nginx-lb nginx-lb [root@kong?~]#
確認結果
可以清晰地看到按照順序，進行輪詢：
[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 ~]#
負載均衡演示實例：權重輪詢
而在此基礎上，進行權重輪詢只需要加上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; >???server?192.168.163.117:7002; #
重啟nginx容器
[root@kong?~]#?docker?restart?nginx-lb nginx-lb [root@kong?~]#
確認結果
可以看到輪詢結果按照1/3和2/3的比重在進行了：
[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 ~]#
