What is the matching logic of Server and Location in Nginx?

Server matching logic

When nginx determines which server block to execute a request, it mainly focuses on the listen and server_name fields in the server block

listen command

The listen field defines the IP and port of the server response. If the listen field is not explicitly configured, the default listening is 0.0.0.0:80 (root) or 0.0.0.0:8080 (Non-root)

listen can be configured as:

1. A combination of ip and port

2. A single ip , the default is to listen to port 80

3. A single port, the default to listen to all ip interfaces

4. A unix socket path

The last item is usually only used to pass requests between different servers

The rules for selecting the server to use are as follows:

1. nginx First, convert all "incomplete" listen instructions, such as those without listen fields into listen 0.0.0.0:80, listen 1.1.1.1 into listen 1.1.1.1:80, etc.

2. nginx creates a server block list that best matches the request based on the requested IP and port. It will first match the server block that specifies a specific IP, and then select the server block that listens to 0.0.0.0. But no matter which case it is , the port must be an exact match

3. If there is only one best match, then the matching server block will be used to respond to the request, otherwise the server_name directive of each server block will be evaluated

Again, the server_name directive will be evaluated only when the listen directive cannot find the best match.

For example, we assume that the example.com domain name points to 192.168.0.1, and nginx located on 192.168.0.1 has and only the following two server blocks:

# server block 1server {
  listen 192.168.0.1;
  server_name other.com
  ...
}

# server block 2server {
  listen 80;
  server_name example.com
  ...
}

server_name directive

If the best match cannot be obtained according to the listen directive, it will Start parsing the server_name directive. nginx will check the "host" header in the request. This value contains the domain name or IP address that the client is actually trying to request. nginx will match the server_name directive based on this value. The matching rules are as follows:

1. nginx will try to find a server block that exactly matches the server_name and host values. If multiple exact matches are found, the first matching server block will be used

2. If no exact matching server block is found, nginx tries to find a server block whose server_name starts with *. If multiple are found, the longest matching server block is selected

3. If If the server block starting with is not found, it will look for the server block ending with. Similarly, if there are multiple matches, the longest match will be selected

4. If no server block matching * is found , it will look for a server block that defines server_name using a regular expression (starting with ~). If multiple matches are found, the first match will be used

5. If no regular expression match is found server block, nginx will select a default server block that matches the listen field. Each IP and port combination can be configured with one and only one default default_server block. If not, the first one in the available list will be selected. A server (the selection at this time is random, the order is not fixed)

Examples are as follows:

(1) Accurate server_name matching, for example:

server {
   listen    80;
   server_name www.domain.com;
   ...
}

(2) String starting with * wildcard:

server {
   listen    80;
   server_name *.domain.com;
   ...
}

(3) String ending with * wildcard:

server {
   listen    80;
   server_name www.*;
   ...
}

(4) Matching regular expression:

server {
   listen    80;
   server_name ~^(?.+)\.domain\.com$;
   ...
}

(5) If none of the above matches, default_server is used. If default_server is not specified, the first available server will be selected. We can specify that when there is no matching host value, an error will be returned to the client. Can be used to prevent others from redirecting spam traffic to your website.

server {
  listen 80  default_server;
  server_name _;  return 444;
}

Let nginx disconnect from the browser by returning 444, the non-standard error code of nginx.

Location matching logic

location syntax analysis

location optional_modifier location_match {
  ...
}

The available modifiers are as follows

Determination rules

1. nginx first checks based on Prefixed location matching (that is, matching that does not include regular expressions)

2. If there is a location block using the = modifier that completely matches the requested URL, the location will be used immediately to respond to the request

3. If no location block match with the = modifier is found, the inexact prefix will continue to be calculated, the longest matching prefix will be found based on the given uri, and then the following processing will be performed:

(1) If The longest matching location has the ^~ modifier, and nginx will immediately use this location to respond to the request

(2) If the longest matching location does not have the ^~ modifier, nginx will temporarily store the match. , and then continue subsequent matching

4. After determining and storing the longest matching prefix location block, nginx continues to check the regular expression matching location (case-sensitive/case-insensitive). If there is a regular expression If the required match is met, the location of the first regular expression matching the requested uri will be selected to respond to the request

5. If no regular expression location matching the requested uri is found, the previous location will be used. The longest stored prefix location response request

Supplement

Normally, once you choose to use a certain location to respond to a request, the request will be processed within that location, regardless of other locations. However, certain instructions in the location will trigger new location matching, such as:

(1)try_files

(2)rewrite

(3)error_page

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