Docker nginx reverse proxy gives "502 Bad Gateway" - docker

Question

I'm trying to have a docker container with nginx work as reverse proxy to other docker containers and I keep getting "Bad Gateway" on locations other other than the base location '/'.
I have the following server block:
server {
listen 80;
location / {
proxy_pass "http://game2048:8080";
}
location /game {
proxy_pass "http://game:9999";
}
}
It works for http://localhost but not for http://localhost/game which gives "Bad Gateway" in the browser and this on the nginx container:
[error] 7#7: *6 connect() failed (111: Connection refused)
while connecting to upstream, client: 172.17.0.1, server: ,
request: "GET /game HTTP/1.1", upstream: "http://172.17.0.4:9999/game",
host: "localhost"
I use the official nginx docker image and put my own configuration on it. You can test it and see all details here:
https://github.com/jollege/ngprox1
Any ideas what goes wrong?
NB: I have set local hostname entries on docker host to match those names:
127.0.1.1 game2048
127.0.1.1 game

Answer 1

I fixed it! I set the server name in different server blocks in nginx config. Remember to use docker port, not host port.
server {
listen 80;
server_name game2048;
location / {
proxy_pass "http://game2048:8080";
}
}
server {
listen 80;
server_name game;
location / {
# Remember to refer to docker port, not host port
# which is 9999 in this case:
proxy_pass "http://game:8080";
}
}
The github repo has been updated to reflect the fix, the old readme file is there under ./README.old01.md.
Typical that I find the answer when I carefully phrase the question to others. Do you know that feeling?

Answer 2

I had the same "502 Bad Gateway" error, but the solution was to tune proxy_buffer_size following this post instructions:
proxy_buffering off;
proxy_buffer_size 16k;
proxy_busy_buffers_size 24k;
proxy_buffers 64 4k;

Answer 3

See the nginx error log
sudo tail -n 100 /var/log/nginx/error.log
If you see Permission denied error in the log like below -
2022/03/28 03:51:09 [crit] 1140954#0: *141 connect() to
xxx.xxx.68.xx:8080 failed (13: Permission denied) while connecting to
upstream, client: xxx.xx.xxx.25, server: www.example.com
See whether the value of httpd_can_network_connect is enabled or not by running the command: sudo getsebool -a | grep httpd
If you see the value of httpd_can_network_connect is off then this is the cause of your issue.
Solution:
set the value of httpd_can_network_connect is on by run the command sudo setsebool httpd_can_network_connect on -P
Hope it will resolve your problem.

Answer 4

I had the same error, but for a web application that was just not serving at the IP and port mentioned in the config.
So say you have this:
location /game {
proxy_pass "http://game:9999";
}
Then make sure the web application that you expect at http://game:9999 is really serving from within a docker container named 'game' and the code is set to serve the app at port 9999.

Answer 5

For me helped this line of code proxy_set_header Host $http_host;
location / {
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;
proxy_set_header Host $http_host;
proxy_set_header X-NginX-Proxy true;
proxy_redirect off;
proxy_pass http://myserver;
}

Answer 6

In my case, after 4 hours, only I missed put the port with semanage command.
location / {
proxy_pass http://A.B.C.D:8090/test;
}
The solution was add 8090 port and works.
semanage port -a -t http_port_t -p tcp 8090

Answer 7

You have to declare an external network if the container you are pointing to is defined in another docker-compose.yml file:
version: "3"
services:
webserver:
image: nginx:1.17.4-alpine
container_name: ${PROJECT_NAME}-webserver
depends_on:
- drupal
restart: unless-stopped
ports:
- 80:80
volumes:
- ./docroot:/var/www/html
- ./nginx-conf:/etc/nginx/conf.d
- certbot-etc:/etc/letsencrypt
networks:
- internal
- my-passwords
networks:
my-passwords:
external: true
name: my-passwords_default
nginx.conf:
server {
listen 80;
server_name test2.com www.test2.com;
location / {
proxy_pass http://my-passwords:3000/;
}
}

Answer 8

You may need to telnet on the upstream machine to check to wither it's connected:
tracing the /var/log/nginx/error.log would help.