Nginx rewrite on docker machine when host port != container port

english
#1

I'm trying to run multiple docker containers all running nginx listening on port 80, but with different host ports mapping to the containers port 80.

For the most part this works, except for when nginx does a redirect due to missing a trailing slash.

server {
    listen 80;
    root /var/www;
    index index.html;
    location /docs {}
}

Given the above nginx config and a docker container running it with host port 8080 mapped to container port 80 I can get localhost:8080/docs/ via curl ok:

> GET /docs/ HTTP/1.1
> User-Agent: curl/7.35.0
> Host: localhost:8080
> Accept: */*
>
< HTTP/1.1 200 OK
* Server nginx/1.9.5 is not blacklisted
< Server: nginx/1.9.5
< Date: Sat, 28 Nov 2015 17:27:05 GMT
< Content-Type: text/html
< Content-Length: 6431
< Last-Modified: Sat, 28 Nov 2015 17:17:06 GMT
< Connection: keep-alive
< ETag: "5659e192-191f"
< Accept-Ranges: bytes
<
... html page ...

but if I request localhost:8080/docs I get a redirect to localhost/docs/

> GET /docs HTTP/1.1
> User-Agent: curl/7.35.0
> Host: localhost:8080
> Accept: */*
>
< HTTP/1.1 301 Moved Permanently
* Server nginx/1.9.5 is not blacklisted
< Server: nginx/1.9.5
< Date: Sat, 28 Nov 2015 17:29:40 GMT
< Content-Type: text/html
< Content-Length: 184
< Location: http://localhost/docs/
< Connection: keep-alive
<
... html redirect page ...

How can I get nginx to preserve the original port when doing the redirect? I've tried looking at port_in_redirect and server_name_in_redirect but they didn't help.

EDIT

Based on https://forum.nginx.org/read.php?2,261216,261216#msg-261216 this doesn't look possible right now.

#2

The HTTP clients will put the port in the Host header. If you use the original value of the host header when doing the redirect, it should work as expected. I tested the following code and looks to be doing exactly what you requested:

location ~ ^.*[^/]$ {
    try_files $uri @rewrite;
}
location @rewrite {
    return 302 $scheme://$http_host$uri/;
}

> GET /bla HTTP/1.1
> User-Agent: curl/7.29.0
> Host: localhost:8080
> Accept: */*
>
< HTTP/1.1 302 Moved Temporarily
< Server: nginx/1.9.7
< Date: Sun, 29 Nov 2015 06:23:35 GMT
< Content-Type: text/html
< Content-Length: 160
< Connection: keep-alive
< Location: http://localhost:8080/bla/
#3

The simplest solution is to remove the index directive and not rely on explicit or implicit $uri/ redirects. For example:

server {
  listen 80;
  root /var/www;
  location /docs {
    try_files $uri $uri/index.html =404;
  }
}

This isn't identical behaviour as it avoids the redirect altogether. If you wanted a trailing slash redirect like the index module gives, then a more complex solution is required. For example:

server {
  listen 80;
  root /var/www;
  location /docs {
    try_files $uri @redirect;
  }
  location @redirect {
    if ($uri ~* ^(.+)/$) { rewrite ^ $uri/index.html last; }
    if (-d $document_root$uri) { return $scheme://$host:8080$uri/; }
    return 404;
  }
}
#4

Just follow this simple fix 

location /app {
    alias /usr/share/nginx/html/folder;
    if (-d $request_filename) {
        rewrite [^/]$ $scheme://$http_host$uri/ permanent;
    }
}
#5

Interesting... I encountered precisely this issue and was able to fix it much as Richard Smith's answer suggests:

root /var/www;
location = /docs {
    try_files $uri $uri/ =404;
}

The only difference is that I don't specify index.html?

Specify the error code to avoid a redirect loop.

Still waiting on feedback from nginx's support.

#6

I think it happens since your Docker is kind of NAT/Proxy to your nginx container. For the routing between different port addition information is required.

For me this was solved add the following to the nginx.conf

http {
    ...
    proxy_set_header Host $http_host; # required for docker client's sake
    proxy_set_header X-Real-IP $remote_addr; # pass on real client's IP
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    ...
}
#7

Ack, just ran into this problem as well. I guess I’ll have to go vanilla nginx or move the stuff on 8080 to something else.

#8

Look into the nginx-proxy container, so you don’t have to do any of this insane port rewriting junk.

#9

I don’t really want anything balancing in front of these containers. I’ve got a docker-compose file that sets the external port based on an env var, and most of the time I just “docker-compose up -d” this file once. However for testing reasons and to allow me to work on other things I want to be able to do “PORT=8080 docker-compose -p test up -d” to spin up a whole new set of containers (due to the new project name) that are mapped to a different host port.