NGINX as a Reverse Proxy
[ 66 ]Introduction to reverse proxying
NGINX can serve as a reverse proxy by terminating requests from clients and
opening new ones to its upstream servers. On the way, the request can be split
up according to its URI, client parameters, or some other logic, in order to best
respond to the request from the client. Any part of the request's original URL
can be transformed on its way through the reverse proxy.
The most important directive when proxying to an upstream server is the proxy_
pass directive. This directive takes one parameter—the URL to which the request
should be transferred. Using proxypass with a URI part will replace the request
uri with this part. For example, /uri in the following example will be transformed
to /newuri when the request is passed on to the upstream:
location /uri {proxy_pass http://localhost:8080/newuri;
}There are two exceptions to this rule, however. First, if the location is defined
with a regular expression, no transformation of the URI occurs. In this example,
the URI /local will be passed directly to the upstream, and not be transformed
to /foreign as intended:
location ~ ^/local {proxy_pass http://localhost:8080/foreign;
}The second exception is that if within the location a rewrite rule changes the URI,
and then NGINX uses this URI to process the request, no transformation occurs.
In this example, the URI passed to the upstream will be /index.php?page=
with
indicated by the URI part of the proxy_pass directive:
location / {rewrite /(.*)$ /index.php?page=$1 break;proxy_pass http://localhost:8080/index;
}The break flag to the rewrite directive is used here to immediately
stop all processing of rewrite module directives.