Webservers/nginx

Nginx

Features

• conditionals - if
• Go-To's - rewrite
• Case statements - map and geo
• inheritance of context configurations - inherit if there is nothing else, otherwise override

Variables

Buildin

• $host - in this order of precedence: host name from the request line, host name from the 'Host' request header field, or the server name matching a request. This is why this can be influenced by a incoming client
• $http_host just host name from the 'Host' request header field.
• $http_<name> - any request header field; name is the field name converted to lower case with dashes replaced by underscores

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;
    . . .
}

Config analyzers

Crossplane - configuration file parser and builder

pip install crossplane

# Analyse
crossplane parse nginx.conf  | jq # turn config into json, will contain results if errors found

# Format and compare differences
vimdiff nginx.conf <(crossplane format nginx.conf)

# Minify, remove comments then format
crossplane format <(crossplane minify nginx.conf)

gixy

# Analyse
ls -1 *conf | xargs gixy | tee gixy.log

Log analyzes

ngxtop

$ ngxtop
running for 411 seconds, 64332 records processed: 156.60 req/sec

Summary:
|   count |   avg_bytes_sent |   2xx |   3xx |   4xx |   5xx |
|---------+------------------+-------+-------+-------+-------|
|   64332 |         2775.251 | 61262 |  2994 |    71 |     5 |

Detailed:
| request_path                             |   count |   avg_bytes_sent |   2xx |   3xx |   4xx |   5xx |
|------------------------------------------+---------+------------------+-------+-------+-------+-------|
| /abc/xyz/xxxx                            |   20946 |          434.693 | 20935 |     0 |    11 |     0 |
| /xxxxx.json                              |    5633 |         1483.723 |  5633 |     0 |

Status module NginxHttpStubStatusModule

References

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