=====
Nginx
=====

Nginx is a high performance HTTP server, alternative to apache httpd.

Apache vs Nginx
===============

htaccess
--------

Not available

Rewrite Rules
-------------

Rewrite rules change part or all of a URL in a client request.

Example:

* Tell the client the content is at a different address: e.g. domain name has changed
* Forward requests to an application server

Apache Rule:
.. code::

    RewriteCond %{HTTP_HOST} example.org
    RewriteRule (.*)         http://www.example.org$1

Nginx Conf
..code::

    server {
        listen      80;
        server_name example.org;
        return      301 http://www.example.org$request_uri;
    }

    server {
        listen      80;
        server_name www.example.org;
        ...
    }


return Directive
----------------

This is simpler, use where possible.

..code::

    server {
        listen 80;
        listen 443 ssl;
        server_name www.old-name.com;
        return 301 $scheme://www.new-name.com$request_uri;
    }

HTTP and HTTPs requests for: ''www.old-name.com'' will result in a 301 redirect (Moved Permanently) to www.new-name.com with the same uri

* http://www.old-name.com > http://www.new-name.com
* http://www.old-name.com/foo/bar > http://www.new-name.com/foo/bar
* https://www.old-name.com/foo/bar > https://www.new-name.com/foo/bar

Redirect returns:
Syntax: return (301 | 302 | 303 | 307) url;

Other HTTP Status with return
Optionally include a message
Syntax: return (1xx | 2xx | 4xx | 5xx) ["text"];
Example: return 401 "Access denied because token is expired or invalid";

Use error_page directive to return a more complex error page

Variables
*********

$scheme = [http|https]
$request_uri = Full URI including arguments

rewrite Directive
-----------------

Permits more complex distinction between URLs
The rewrite directive is like a return directive and decarled in a server or location block.
Syntax: rewrite regex URL [flag];
rewrite can only return HTTP 301 or 302, to include more you need to use a rewrite with a return
rewrite doesn't stop NGINX's processing, like return does

Example:

Match a URI starting '/download' and including '/media/' or '/audio/' it then rewrites this this to /mp3/ and
adds the appropriate extension .mp3 (audio) or .ra (media).

If no URL is matched return a 403

..code::

    server {
        ...
        rewrite ^(/download/.*)/media/(.*)\..*$ $1/mp3/$2.mp3 last;
        rewrite ^(/download/.*)/audio/(.*)\..*$ $1/mp3/$2.ra  last;
        return  403;
        ...
    }

/download/cdn-west/media/file1 becomes /download/cdn-west/mp3/file1.mp3

Flags
*****

You can add flags to the end of a rewrite rule, last is shown as such a flag, shown above.

last
    Skip any subsequent rewrite directives in the current server/location block (make this the last).

try_files directive
-------------------

Placed in a server or location block.
Takes a list of one or more files and directories and a final URI.
Directories are indicated by a trailing slash.
Syntax: try_files file … uri;

 * https://www.nginx.com/blog/creating-nginx-rewrite-rules/
 * https://www.nginx.com/blog/converting-apache-to-nginx-rewrite-rules/
 * http://nginx.org/en/docs/http/ngx_http_rewrite_module.html
 * https://github.com/flygoast/ngx_http_types_filter

.. code::

    location ~ /logatom/logs/.*/.*/httpaccess_.*$ {
    #rewrite ^/logs/(.*) /$1;
    #try_files $uri =404;
    root /usr/cachelogic/log/traffic_logs/processed;
    }