How Nginx Decides Which Server Block Will Handle a Request

Published by powerfulyang on Dec 24, 2020

Respect to Understanding Nginx Server and Location Block Selection Algorithms

Parsing the “server_name” Directive to Choose a Match

Next, to further evaluate requests that have equally specific listen directives, Nginx checks the request’s “Host” header. This value holds the domain or IP address that the client was actually trying to reach.

Matching Location Blocks

Similar to the process that Nginx uses to select the server block that will process a request, Nginx also has an established algorithm for deciding which location block within the server to use for handling requests.

Location Block Syntax

Location blocks generally take the following form:

nginx
1location optional_modifier location_match {
2
3    . . .
4
5}

The modifiers below will cause the associated location block to be interpreted as follows:

  • (none) : If no modifiers are present, the location is interpreted as a prefix match. This means that the location given will be matched against the beginning of the request URI to determine a match.
  • = : If an equal sign is used, this block will be considered a match if the request URI exactly matches the location given. = 开头表示精确匹配，只有完全匹配上才能生效
  • ~ : If a tilde modifier is present, this location will be interpreted as a case-sensitive regular expression match. ~ 开头表示区分大小写的正则匹配
  • ~* : If a tilde and asterisk modifier is used, the location block will be interpreted as a case-insensitive regular expression match. ~* 开头表示不区分大小写的正则匹配
  • ^~ : If a carat and tilde modifier is present, and if this block is selected as the best non-regular expression match, regular expression matching will not take place. ^~ 开头对URL路径进行前缀匹配，并且在正则之前。
  • /uri : 不带任何修饰符，也表示前缀匹配，但是在正则匹配之后
  • / : 通用匹配，任何未匹配到其它location的请求都会匹配到，相当于switch中的default

When Does Location Block Evaluation Jump to Other Locations?

Another instance where the processing location may be reevaluated is with the try_files directive. This directive tells Nginx to check for the existence of a named set of files or directories. The last parameter can be a URI that Nginx will make an internal redirect to.

Consider the following configuration:

nginx
1root /var/www/main;
2location / {
3    try_files $uri $uri.html $uri/ /fallback/index.html;
4}
5
6location /fallback {
7    root /var/www/another;
8}

proxy_pass 反向代理配置中 url 后面加不加 / 的说明

path 后面加 /

nginx
1location  /proxy/ {
2          proxy_pass http://192.168.1.5:8090/;
3}

这样，访问 http://192.168.1.23/proxy/ 就会被代理到 http://192.168.1.5:8090/ 匹配的proxy目录不需要存在根目录 /var/www/main 里面。
注意

nginx
1location  /proxy/ {
2          proxy_pass http://192.168.1.5:8090;
3}

这样配置后，访问 http://192.168.1.23/proxy/ 就会被反向代理到 http://192.168.1.5:8090/proxy/

nginx
1location  /proxy/ {
2          proxy_pass http://192.168.1.5:8090/haha/;
3}

这样配置的话，访问 http://103.110.186.23/proxy/ 代理到 http://192.168.1.5:8090/haha/

nginx
1location  /proxy/ {
2          proxy_pass http://192.168.1.5:8090/haha;
3}

上面配置后，访问 http://192.168.1.23/proxy/index.html 就会被代理到 http://192.168.1.5:8090/hahaindex.html
同理，访问 http://192.168.1.23/proxy/test.html 就会被代理到 http://192.168.1.5:8090/hahatest.html
注意，这种情况下，不能直接访问 http://192.168.1.23/proxy/ 后面就算是默认的 index.html 文件也要跟上，否则访问失败！

path路径后面不带 /

nginx
1location  /proxy {
2          proxy_pass http://192.168.1.5:8090/;
3}
nginx
1location  /proxy {
2          proxy_pass http://192.168.1.5:8090;
3}

这样配置的话，浏览器访问 http://103.110.186.23/proxy 会自动加上 "/"（ 即变成 http://103.110.186.23/proxy/ ），代理到 http://192.168.1.5:8090/proxy/

nginx
1location  /proxy {
2          proxy_pass http://192.168.1.5:8090/haha/;
3}

这样配置的话，浏览器访问 http://103.110.186.23/proxy 会自动加上 "/"（ 即变成 http://103.110.186.23/proxy/ ），代理到 http://192.168.1.5:8090/haha/

nginx
1location  /proxy {
2          proxy_pass http://192.168.1.5:8090/haha;
3}

这样配置的话，浏览器访问 http://103.110.186.23/proxy ，和第三种结果一样，同样被代理到 http://192.168.1.5:8090/haha/