Jenkins With Nginx Reverse Proxy And Resolver - nginx

Question

I am running Jenkins inside Docker behind an Nginx reverse proxy. Now I got a problem with the resolver.
When I activate the resolver with:
set $backend "http://jenkins:8080/";
proxy_pass $backend;
I will get the following error for all javascript files:
Refused to execute script from 'http://localhost/static/....js' because its MIME type ('text/html') is not executable, and strict MIME type checking is enabled.
When I simply proxy pass without resolver:
proxy_pass http://jenkins:8080/;
It works but without resolver. The resolver is mandatory otherwise the setup won't work when the host jenkins changes it's Ip (Docker DNS Server).
My configuration:
resolver 127.0.0.11 ipv6=off valid=30s;
client_max_body_size 100m;
keepalive_timeout 65;
types_hash_max_size 2048;
server {
listen 80 default_server;
listen [::]:80 default_server;
server_name _;
location / {
set $backend "http://jenkins:8080/";
proxy_pass $backend;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
}
}

Answer 1

Based on the error message you receive, it sounds like you're getting HTML pages in place of JavaScript.
Using a proxy_pass paradigm with a variable, you're telling nginx that it shouldn't mess with the value any further, e.g., regardless of the location and the URI, all requests to your backend will always be just as the variable says (e.g., with the same URI in your case).
The best option would probably be to use $uri, $is_args and $args, as per NGINX proxy_pass remove path prefix & resolve DNS:
- set $backend "http://jenkins:8080/";
- proxy_pass $backend;
+ proxy_pass http://jenkins:8080$uri$is_args$args;
Another option, which potentially could be less secure, is to use $uri_request, which has a slightly different meaning than the plain $uri in certain limited cases, as per Nginx pass_proxy subdirectory without url decoding:
proxy_pass http://jenkins:8080$request_uri;