The details in this question are getting long, but I think it narrows down to this:
For some reason the host name matters to Nginx when it's trying to figure out whether to proxy the request. If the host name is set to git.example.com the request does not seem to go through, but if it's set to 203.0.113.2 then it goes through. Why does the host name matter?
Filed an issue with Nginx here And docker compose
When I type in the IP address of the reverse proxy directly into my browser bar, it does perform the redirect.
When using a URL that is resolved via the /etc/hosts entry 203.0.113.2 git.example.com the "Welcome to Ngnix page" is shown. Any ideas? This is the configuration:
server {
listen 203.0.113.2:80 default_server;
server_name 203.0.113.2 git.example.com;
proxy_set_header X-Real-IP $remote_addr; # pass on real client IP
location / {
proxy_pass http://203.0.113.1:3000;
}
}
This is the docker-compose.yml file that is used to launch the whole thing:
version: '3'
services:
gogs-nginx:
build: ./proxy
ports:
- "80:80"
networks:
mk1net:
ipv4_address: 203.0.113.2
gogs:
image: gogs/gogs
ports:
- "3000:3000"
volumes:
- gogs-data:/data
networks:
mk1net:
ipv4_address: 203.0.113.3
volumes:
gogs-data:
external: true
networks:
mk1net:
ipam:
config:
- subnet: 203.0.113.0/24
One interesting thing is that I can navigate to for example:
http://203.0.113.2/issues
The log for the above URL is:
gogs-nginx_1 | 203.0.113.1 - - [07/Oct/2018:11:28:06 +0000] "GET / HTTP/1.1" 200 38825 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36" "-"
If I then change 203.0.113.2 with git.example.com (So that the url ends up being git.example.com I get Nginxs "404 not found" page, and the log says:
gogs-nginx_1 | 2018/10/07 11:31:34 [error] 8#8: *10 open() "/usr/share/nginx/html/issues" failed (2: No such file or directory), client: 203.0.113.1, server: localhost, request: "GET /issues HTTP/1.1", host: "git.example.com"
If I only use http://git.example.com as the URL I get the NGINX welcome page, and the following log:
gogs-nginx_1 | 203.0.113.1 - - [07/Oct/2018:11:34:39 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36" "-"
It looks like Nginx understands that the request is for the proxy because it logs the IP of the proxy, but it does not redirect to the proxy and returns a 304 ...
Using curl with a host name parameter that targets the proxy like this:
curl -H 'Host: git.example.com' -si http://203.0.113.2
Results in the Nginx welcome page:
ole@mki:~/Gogs/.gogs/docker$ curl -H 'Host: git.example.com' -si http://203.0.113.2
HTTP/1.1 200 OK
Server: nginx/1.15.1
Date: Sun, 07 Oct 2018 17:09:11 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 03 Jul 2018 13:27:08 GMT
Connection: keep-alive
ETag: "5b3b79ac-264"
Accept-Ranges: bytes
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
But if I change the host name to the ip address like this:
Using curl with a host name parameter that targets the proxy like this:
curl -H 'Host: 203.0.113.2' -si http://203.0.113.2
Then the proxy works as it should:
ole@mki:~/Gogs/.gogs/docker$ curl -H 'Host: 203.0.113.2' -si http://203.0.113.2
HTTP/1.1 302 Found
Server: nginx/1.15.1
Date: Sun, 07 Oct 2018 17:14:46 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 34
Connection: keep-alive
Location: /user/login
Set-Cookie: lang=en-US; Path=/; Max-Age=2147483647
Set-Cookie: i_like_gogits=845bb09d69587b81; Path=/; HttpOnly
Set-Cookie: _csrf=neGgBfG4LdOcdrdeA0snHjVGz4s6MTUzODkzMjQ4NjE5MzEzNzI3OQ%3D%3D; Path=/; Expires=Mon, 08 Oct 2018 17:14:46 GMT; HttpOnly
Set-Cookie: redirect_to=%252F; Path=/
<a href="/user/login">Found</a>.
I am sorry, I failed to realize what's happening on your side because the information is sometimes confusing and sometimes incomplete. But Stackoverflow provides a great explanation on what is considered a good question: How to create a Minimal, Complete, and Verifiable example and so I have just tried to implement a minimal example of a system you are likely going to build.
Below I am providing all the files and will show you a test run as well.
docker-compose.ymlgogs:
image: gogs/gogs
web:
build: .
ports:
- 8000:80
links:
- gogs
I have outdated Docker at my computer and I do not want to bother with Docker networking, so I have just linked both containers using Docker links. This is the most important part and the link will ensure that (1) our web container depends on gogs; (2) we are able to reference gogs IP from inside web as just gogs. Docker will resolve the name to an IP assigned to the container.
Since I want a minimal example, I've skipped everything else as irrelevant. For example, volume.
DockerfileNewer Compose versions support config options specified right in docker-compose.yml, but I need a custom Dockerfile instead. It's trivial:
FROM nginx:stable-alpine
COPY gogs.conf /etc/nginx/conf.d
gogs.confAnd finally we need Nginx configuration for proxy:
server {
listen 80 default_server;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
location / {
proxy_pass http://gogs:3000;
}
}
You may notice here we are referring another container simply by name gogs and we need to know what port number it is exposes. We know: 3000.
$ docker-compose build
$ docker-compose up
It's up and running:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1f74293df630 g_web "nginx -g 'daemon off" 2 minutes ago Up 26 seconds 0.0.0.0:8000->80/tcp g_web_1
dfa2dbaa6074 gogs/gogs "/app/gogs/docker/sta" 2 minutes ago Up 26 seconds 22/tcp, 3000/tcp g_gogs_1
web container is exposed to the world at port number 8000.
Let's request it by IP:
$ curl -si http://192.168.99.100:8000/
HTTP/1.1 302 Found
Server: nginx/1.14.0
Date: Sun, 07 Oct 2018 15:13:55 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 31
Connection: keep-alive
Location: /install
Set-Cookie: lang=en-US; Path=/; Max-Age=2147483647
Set-Cookie: i_like_gogits=50411f542e2ae8f8; Path=/; HttpOnly
Set-Cookie: _csrf=ZJxRPqnqayIbpAYgZ22zrPIOaSo6MTUzODkyNTIzNTQ2NTg5MDE1NA%3D%3D; Path=/; Expires=Mon, 08 Oct 2018 15:13:55 GMT; HttpOnly
<a href="/install">Found</a>.
Corresponding log file:
web_1 | 192.168.99.1 - - [07/Oct/2018:15:14:24 +0000] "GET / HTTP/1.1" 302 31 "-" "curl/7.61.1" "-"
gogs_1 | [Macaron] 2018-10-07 15:14:24: Started GET / for 192.168.99.1
gogs_1 | [Macaron] 2018-10-07 15:14:24: Completed GET / 302 Found in 199.519µs
gogs_1 | 2018/10/07 15:14:24 [TRACE] Session ID: 38d06d393a9e9d21
gogs_1 | 2018/10/07 15:14:24 [TRACE] CSRF Token: Xth986dFWhhj8w8vBdIqRZu4SbI6MTUzODkyNTI2NDYxMDYzNzAyNA==
I can see from the log that (1) both containers work and they were used to process the request; (2) 192.168.99.1 is my host's IP address, which means "gogs" successfully gets a real request IP via X-Forwarded-For.
OK, let's request using a domain name:
$ curl -H 'Host: g.example.com' -si http://192.168.99.100:8000/
Trust me, this is just sufficient. Host is an HTTP protocol header to pass domain name. And any browser will do the same under the hood.
and the corresponding log file is --
gogs_1 | [Macaron] 2018-10-07 15:32:49: Started GET / for 192.168.99.1
gogs_1 | [Macaron] 2018-10-07 15:32:49: Completed GET / 302 Found in 618.701µs
gogs_1 | 2018/10/07 15:32:49 [TRACE] Session ID: 81f64d97e9c3dd1e
gogs_1 | 2018/10/07 15:32:49 [TRACE] CSRF Token: X5QyHM4LMIfn8OSJD1gwSSEyXV46MTUzODkyNjM2OTgyODQyMjExMA==
web_1 | 192.168.99.1 - - [07/Oct/2018:15:32:49 +0000] "GET / HTTP/1.1" 302 31 "-" "curl/7.61.1" "-"
No changes, everything works as expected.