View source for Webservers/nginx

= Nginx =
== Features ==
* conditionals - <code>if</code>
* Go-To's - <code>rewrite</code>
* Case statements - <code>map</code> and <code>geo</code>
* inheritance of context configurations - inherit if there is nothing else, otherwise override

== Operations ==
<source lang=bash>
nginx -v
sudo nginx -t
sudo systemctl status nginx
sudo systemctl reload nginx
sudo nginx -s reload #  0.7.53+
</source>

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

== [https://www.digitalocean.com/community/tutorials/understanding-nginx-server-and-location-block-selection-algorithms server context] match order ==
For the <code>server {}</code> context selection nginx algorithm takes only 2 directives into account <code>listen</code> and <code>server_name</code>.
server {
    listen 80;
    server_name *.example.com;
    . . .
}


;Matching <code>listen</code> directive
At first <code>listen</code> directive is parsed, during this step any "incomplete" directives are added with default values
* no-ip -> set with <code>0.0.0.0</code>
* no-port -> set with port <code>:80</code>


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 <code>listen</code> directive match gets chosen.


;Matching <code>server_name</code> directive
If there are multiple the same listen directives, then <code>server_name</code> is being parsed in this order:
* exact match host header from the request
* leading wildcard (indicated by a <code>*</code> 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 <code>*</code> in the config). If multiple matches are found, the longest match will be used to serve the request.
* using regular expressions (indicated by a <code>~</code> 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 <code>default_server</code> block for that IP address and port part of listen directive. There can be only one <code>default_server</code> 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). 


<source lang=json>
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;
    . . .
}
</source>

= Config analyzers =
;[https://github.com/nginxinc/crossplane Crossplane] - configuration file parser and builder
<source lang=bash>
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)
</source>


;[https://github.com/yandex/gixy gixy]
<source lang=bash>
# Analyse
ls -1 *conf | xargs gixy | tee gixy.log
</source>
= Log analyzes =
; [https://github.com/lebinh/ngxtop ngxtop]
<source lang=bash>
$ 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 |
</source>


; Status module [https://wiki.nginx.org/NginxHttpStubStatusModule NginxHttpStubStatusModule]
=References=
*[https://serverfault.com/questions/527630/what-is-the-different-usages-for-sites-available-vs-the-conf-d-directory-for-ngi Sites-enabled vs conf.d] Explanation of standards and Debian-ism of <tt>sites-enabled</tt>.