Webservers/nginx

Nginx

server context match order

For the server {} context selection nginx algorithm takes only 2 directives into account listen and server_name. server {

   listen 80;
   server_name *.example.com;
   . . .

}

Matching listen directive

At first listen directive is parsed, during this step any "incomplete" directives are added with default values

• no-ip -> set with 0.0.0.0
• no-port -> set with port :80

The listen directive can be set to:

• An IP address/port combo.
• A lone IP address which will then listen on the default port 80.
• A lone port which will listen to every interface on that port.
• The path to a Unix socket

The most accurate listen directive match gets chosen.

Matching server_name directive

If there are multiple the same listen directives, then server_name is being parsed in this order:

• exact match host header from the request
• leading wildcard (indicated by a * at the beginning of the name in the config). If multiple matches are found, the longest match will be used to serve the request.
• trailing wildcard (indicated by a server name ending with a * in the config). If multiple matches are found, the longest match will be used to serve the request.
• using regular expressions (indicated by a ~ before the name). The first server_name with a regular expression that matches the “Host” header will be used to serve the request.
• selects the default_server block for that IP address and port part of listen directive. There can be only one default_server declaration per each IP address/port combination.
• First block, for an IP address/port combo, this will either be the first block in the configuration or the block that contains the default_server option as part of the listen directive (which would override the first-found algorithm).

server {
    listen 80 default_server;
    server_name example.com;
    . . .
}
server {
    listen 80;
    server_name ~^(subdomain|set|www|host1).*\.example\.com$;
    . . .
}
server {
    listen 80;
    server_name www.example.*;
    . . .
}
server {
    listen 80;
    server_name *.org;
    . . .
}

References

• Sites-enabled vs conf.d Explanation of standards and Debian-ism of sites-enabled.