Proxying RabbitMQ Management UI Through Nginx (Fixing the %2F Problem)

The Problem

When you put RabbitMQ's Management UI behind an nginx reverse proxy under a
sub-path like /rabbitmq/, queue detail pages and many API calls break silently.

The root cause: nginx normalizes the request URI before proxying. It decodes
%2F (the URL-encoded forward slash) into a literal /. RabbitMQ's Management
API uses %2F to represent the default virtual host (/) in API paths:

GET /api/queues/%2F/my-queue

When nginx decodes it:

GET /api/queues///my-queue   ← broken

What Doesn't Work

The common advice of using merge_slashes off or a rewrite directive doesn't
fully solve this because nginx still normalizes $uri before forwarding.

The Fix

Use $request_uri inside an if block. Unlike $uri, $request_uri holds
the raw, undecoded URI exactly as the client sent it — nginx never touches it.

nginx
# RabbitMQ: API paths — use $request_uri to preserve %2F (never decoded by nginx)
location ~* ^/rabbitmq/api/ {
    if ($request_uri ~* "^/rabbitmq/(.*)") {
        proxy_pass http://rabbitmq:15672/$1;
    }
    proxy_buffering off;
    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 https;
}

# RabbitMQ: general UI (JS, CSS, static assets, non-API pages)
location ~* ^/rabbitmq/ {
    rewrite ^/rabbitmq/(.*)$ /$1 break;
    proxy_pass http://rabbitmq:15672;
    proxy_buffering off;
    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 https;
}