Location matching and rewrite rewrite jump in Nginx

1. Common Nginx regular expressions

^ ：匹配输入字符串的起始位置
$ ：匹配输入字符串的结束位置
* ：匹配前面的字符零次或多次。如“ol*”能匹配“o”及“ol”、“oll”
+ ：匹配前面的字符一次或多次。如“ol+”能匹配“ol”及“oll”、“olll”，但不能匹配“o”
? ：匹配前面的字符零次或一次，例如“do(es)?”能匹配“do”或者“does”，”?”等效于”{0,1}”
. ：匹配除“\n”之外的任何单个字符，若要匹配包括“\n”在内的任意字符，请使用诸如“[.\n]”之类的模式
\ ：将后面接着的字符标记为一个特殊字符或一个原义字符或一个向后引用。如“\n”匹配一个换行符，而“\$”则匹配“$”
\d ：匹配纯数字
{n} ：重复 n 次
{n,} ：重复 n 次或更多次
{n,m} ：重复 n 到 m 次
[] ：定义匹配的字符范围
[c] ：匹配单个字符 c
[a-z] ：匹配 a-z 小写字母的任意一个
[a-zA-Z0-9] ：匹配所有大小写字母或数字
() ：表达式的开始和结束位置
| ：或运算符

Two, location

1. Location classification

精准匹配：location = / {}
一般匹配：location / {}
正则匹配：location ~ / {}

2. Commonly used matching rules for location

=   :进行普通字符精确匹配，也就是完全匹配。
^~  :表示普通字符匹配。使用前缀匹配。如果匹配成功，则不再匹配其它 location。
~   :区分大小写的匹配。
~*  :不区分大小写的匹配。
!~  :区分大小写的匹配取非。
!~* :不区分大小写的匹配取非。

3. Location priority

首先精确匹配 =
其次前缀匹配 ^~
其次是按文件中顺序的正则匹配 ~或~*
然后匹配不带任何修饰的前缀匹配
最后是交给 / 通用匹配

4. Location example description

（1）location = / {}
=为精确匹配 / ，主机名后面不能带任何字符串，比如访问 / 和 /data，则 / 匹配，/data 不匹配
再比如 location = /abc，则只匹配/abc ，/abc/或 /abcd不匹配。若 location  /abc，则即匹配/abc 、/abcd/ 同时也匹配 /abc/。

（2）location / {}
因为所有的地址都以 / 开头，所以这条规则将匹配到所有请求 比如访问 / 和 /data, 则 / 匹配， /data 也匹配，
但若后面是正则表达式会和最长字符串优先匹配（最长匹配）

（3）location /documents/ {}
匹配任何以 /documents/ 开头的地址，匹配符合以后，还要继续往下搜索其它 location
只有其它 location后面的正则表达式没有匹配到时，才会采用这一条

（4）location /documents/abc {}
匹配任何以 /documents/abc 开头的地址，匹配符合以后，还要继续往下搜索其它 location
只有其它 location后面的正则表达式没有匹配到时，才会采用这一条

（5）location ^~ /images/ {}
匹配任何以 /images/ 开头的地址，匹配符合以后，停止往下搜索正则，采用这一条

（6）location ~* \.(gif|jpg|jpeg)$ {}
匹配所有以 gif、jpg或jpeg 结尾的请求
然而，所有请求 /images/ 下的图片会被 location ^~ /images/ 处理，因为 ^~ 的优先级更高，所以到达不了这一条正则

（7）location /images/abc {}
最长字符匹配到 /images/abc，优先级最低，继续往下搜索其它 location，会发现 ^~ 和 ~ 存在

（8）location ~ /images/abc {}
匹配以/images/abc 开头的，优先级次之，只有去掉 location ^~ /images/ 才会采用这一条

（9）location /images/abc/1.html {}
匹配/images/abc/1.html 文件，如果和正则 ~ /images/abc/1.html 相比，正则优先级更高

优先级总结：
(location =) > (location 完整路径) > (location ^~ 路径) > (location ~,~* 正则顺序) > (location 部分起始路径) > (location /)

5. In actual website usage, there are at least three matching rule definitions

The first mandatory rule
directly matches the root of the website. It is more frequent to visit the homepage of the website through the domain name. Using this will speed up the processing, such as the official website.
This is directly forwarded to the back-end application server, or it can be a static homepage

location = / {
    proxy_pass http://tomcat_server/;
}

The second mandatory rule
handles static file requests, which is the strength of nginx as an http server.
There are two configuration modes, directory matching or suffix matching, choose one of them or use them together

location ^~ /static/ {
    root /webroot/static/;
}

location ~* \.(html|gif|jpg|jpeg|png|css|js|ico)$ {
    root /webroot/res/;
}

The third rule is a
general rule, such as forwarding dynamic requests with .php and .jsp suffixes to the back-end application server.
Non-static file requests are dynamic requests by default.

location / {
    proxy_pass http://tomcat_server;
}

Three, rewrite

The rewrite function is to use global variables provided by nginx or variables set by yourself, combined with regular expressions and tags to achieve URL rewriting and redirection.
For example: after changing the domain name, the old domain name needs to be able to be transferred to the new domain name, a certain webpage needs to be redirected to a new page after a change, the website anti-theft chain, etc. needs.

Rewrite can only be placed in server{}, location{}, if{}, and by default can only work on the string after the domain name except for the passed parameters.
For example: http://www.kgc.com/a/we/index.php?id=1&u=str only rewrites /a/we/index.php.

1. Rewrite jump implementation

• Nginx: supports URL rewriting and judgment of if conditions through the ngx_http_rewrite_module module, but does not support else
• Jump: Jump from one location to another location, the loop can be executed up to 10 times, after exceeding, nginx will return a 500 error
• PCRE support: Perl compatible regular expression grammar rule matching
• Rewrite module set instruction: create new variables and assign values ​​to them

2. Rewrite execution order

1. Execute the rewrite instruction in the server block
2. Execute location matching
3. Execute the rewrite instruction in the selected location

3. Rewrite syntax format

语法rewrite<regex><replacement><flag>;
regex:表示正则匹配规则
replacement:表示跳转后的内容
flag:表示rewrite支持的flag标记

4. Flag description

last: After this rule is matched, continue to match the new location URI rule downwards, generally used in server and if.
break: This rule will be terminated when the matching is completed, and will no longer match any subsequent rules. It is generally used in location.
redirect: Return to a 302 temporary redirect, the browser address will display the redirected URL address.
permanent: Return to 301 permanent redirection, and the URL address after the redirection will be displayed in the address bar of the browser.

5. Rewrite example

Domain-based redirect

Now the company’s old domain name www.test.com has business requirements changes and needs to be replaced with a new domain name www.kgc.com, but the old domain name cannot be abolished, it needs to be redirected to the new domain name, and the following parameters remain unchanged.

vim /usr/local/nginx/conf/nginx.conf
server {
	listen       80;
	server_name  www.test.com;
	charset utf-8;
	access_log  /var/log/nginx/www.test.com.access.log;
	location / {
	    if ($host = 'www.test.com'){
	        rewrite ^/(.*)$ http://www.kgc.com/$1 permanent;
	    }
        root   html;
        index  index.html index.htm;
    }
}

echo "192.168.109.3 www.kgc.com www.test.com" >> /etc/hosts

systemctl restart nginx

The browser input simulated visit http://www.test.com/1.html
will jump to www.lisi.com/1.html, check the element and you can see the return 301, which realizes the permanent redirection and the domain name The following parameters also jump normally.

Access redirect based on client IP

Today, the new version of the company’s business is online, requiring all IPs to access any content to display a fixed maintenance page, and only the company’s IP: 192.168.109.3 is accessible.

vim /usr/local/nginx/conf/nginx.conf
server {
	listen       80;
	server_name  www.test.com;
	charset utf-8;
	access_log  /var/log/nginx/www.test.com.access.log;

	#设置是否合法的IP标记;设置变量$rewrite，变量值为boole值true
    set $rewrite true;
    #判断是否为合法IP;当客户端IP为192.168.109.3时，将变量值设为false，不进行重写
    if ($remote_addr = "192.168.109.3"){
        set $rewrite false;
    }
	#除了合法IP，其它都是非法IP，进行重写跳转维护页面
	#当变量值为true时，进行重写
    if ($rewrite = true){
        #重写在访问IP后边插入/weihu.html，例如192.168.184.11/weihu.html
        rewrite (.+) /weihu.html;
    }
    location = /weihu.html {
        #网页返回/var/www/html/weihu.html的内容
        root /var/www/html;
    }
	location / {
        root   html;
        index  index.html index.htm;
    }
}

mkdir -p /var/www/html/
echo 'weihu!' > /var/www/html/weihu.html
echo "192.168.109.3 www.test.com" >> /etc/hosts
systemctl restart nginx

Browser access
Only IP 192.168.163.10 can be accessed normally, other addresses are maintenance pages

Jump to the new domain name based on the old domain name and add a directory

Now you are visiting http://kgc.test.com, now you need to redirect all visits under this domain name to http://www.test.com/kgc

vim /usr/local/nginx/conf/nginx.conf
server {
	listen       80;
	server_name  kgc.test.com;
	charset utf-8;
	access_log  /var/log/nginx/kgc.test.com.access.log;
	#添加;这里的$1为位置变量，代表/post
	location /post {
        rewrite (.+) http://www.test.com/kgc$1 permanent;
    }
	location / {
        root   html;
        index  index.html index.htm;
    }
}

mkdir -p /usr/local/nginx/html/kgc/post
echo "this is 1.html" > /usr/local/nginx/html/kgc/post/1.html
echo "192.168.109.3 kgc.test.com www.test.com" >> /etc/hosts
systemctl restart nginx.service

Use a browser to visit
http://kgc.test.com/post/1.html to jump to http://www.test.com/kgc/post/1.html

Jump based on parameter matching

Now visit http://www.test.com/100-(100|200)-100 (any number).html to jump to http://www.test.com page.

vim /usr/local/nginx/conf/nginx.conf
server {
	listen       80;
	server_name  www.test.com;
	charset utf-8;
	access_log  /var/log/nginx/www.test.com.access.log;

    if ($request_uri ~ ^/100-(100|200)-(\d+).html$) {
        rewrite (.+) http://www.test.com permanent;
    }

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

echo "192.168.109.3 www.test.com" >> /etc/hosts
systemctl restart nginx

Browser visit
http://www.test.com/100-200-100.html or
http://www.test.com/100-100-100.html to jump to http://www.test.com page.

Jump based on all the files ending with php in the directory

Request to visit http://www.test.com/upload/123.php to jump to the homepage.

vim /usr/local/nginx/conf/nginx.conf
server {
	listen       80;
	server_name  www.test.com;		#域名修改	
	charset utf-8;
	access_log  /var/log/nginx/www.test.com-access.log;
	
location ~* /upload/.*\.php$ {
    rewrite (.+) http://www.test.com permanent;
}

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

echo "192.168.109.3 www.test.com" >> /etc/hosts
systemctl restart nginx