Nginx with docker: Reverse Proxy doesn't work - docker

Question

I recently want to set a reverse proxy server. I pulled a nginx docker image and I ran the docker container using this command:
docker run -d --name ngtest -p 4080:80 nginx
Then I updated the /etc/nginx/nginx.conf like below:
user nginx;
worker_processes 1;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/access.log main;
sendfile on;
#tcp_nopush on;
keepalive_timeout 65;
#gzip on;
include /etc/nginx/conf.d/*.conf;
server{
listen 80;
location /nexus/ {
proxy_pass http://192.168.0.30:8081/;
}
}
}
The container works after restarted, when I tried to open page
http://192.168.0.30:4080, I got the default Nginx page.
However when I tried this url: http://192.168.0.30:4080/nexus, I got a 404 page with errors.
From the log, it looks that the nginx didn't forward the url to the page I set in nginx.conf, instead it tried to look the page in the local directory:
2020/03/11 16:10:34 [error] 6#6: *251 open() "/usr/share/nginx/html/nexus" failed (2: No such file or directory), client: 192.168.0.153, server: localhost, request: "GET /nexus HTTP/1.1", host: "192.168.0.30:4080"
192.168.0.153 - - [11/Mar/2020:16:10:34 +0000] "GET /nexus HTTP/1.1" 404 555 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.132 Safari/537.36" "-"
Is there anything wrong in my steps?
Thanks,
Alex

Answer 1

The issue is that even with your updated config you are still doing:
include /etc/nginx/conf.d/*.conf;
Which is loading /etc/nginx/conf.d/default.conf which will be the default server in the event no server name is provided based on the rules of determining the server to use if server name not found.
You should do something like:
Save to a config file your server definition of:
server{
listen 80;
location /nexus/ {
proxy_pass http://192.168.0.30:8081/;
}
}
Then run
docker run -d -p 4080:80 -v (path_to_your_config):/etc/nginx/conf.d/default.conf nginx
This will replace the default config with yours. Then if you need to make changes you just make them and restart the container.