I tried using the popular Jason Wilder reverse proxy that code-magically works for everyone, and learned that it doesn't work for everyone (ie: me). And I'm brand new to NGINX, and didn't like that I didn't understand the technologies I was trying to use.
Wanted to add my 2 cents, because the discussion above around linking containers together is now dated since it is a deprecated feature. So here's an explanation on how to do it using networks. This answer is a full example of setting up nginx as a reverse proxy to a statically paged website using Docker Compose and nginx configuration.
Add the services that need to talk to each other onto a predefined network. For a step-by-step discussion on Docker networks, I learned some things here: https://technologyconversations.com/2016/04/25/docker-networking-and-dns-the-good-the-bad-and-the-ugly/
First of all, we need a network upon which all your backend services can talk on. I called mine web but it can be whatever you want.
docker network create web
We'll just do a simple website app. The website is a simple index.html page being served by an nginx container. The content is a mounted volume to the host under a folder content
DockerFile:
FROM nginx
COPY default.conf /etc/nginx/conf.d/default.conf
default.conf
server {
listen 80;
server_name localhost;
location / {
root /var/www/html;
index index.html index.htm;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /usr/share/nginx/html;
}
}
docker-compose.yml
version: "2"
networks:
mynetwork:
external:
name: web
services:
nginx:
container_name: sample-site
build: .
expose:
- "80"
volumes:
- "./content/:/var/www/html/"
networks:
default: {}
mynetwork:
aliases:
- sample-site
Note that we no longer need port mapping here. We simple expose port 80. This is handy for avoiding port collisions.
Fire this website up with
docker-compose up -d
Some fun checks regarding the dns mappings for your container:
docker exec -it sample-site bash
ping sample-site
This ping should work, inside your container.
Nginx Reverse Proxy:
Dockerfile
FROM nginx
RUN rm /etc/nginx/conf.d/*
We reset all the virtual host config, since we're going to customize it.
docker-compose.yml
version: "2"
networks:
mynetwork:
external:
name: web
services:
nginx:
container_name: nginx-proxy
build: .
ports:
- "80:80"
- "443:443"
volumes:
- ./conf.d/:/etc/nginx/conf.d/:ro
- ./sites/:/var/www/
networks:
default: {}
mynetwork:
aliases:
- nginx-proxy
Fire up the proxy using our trusty
docker-compose up -d
Assuming no issues, then you have two containers running that can talk to each other using their names. Let's test it.
docker exec -it nginx-proxy bash
ping sample-site
ping nginx-proxy
Last detail is to set up the virtual hosting file so the proxy can direct traffic based on however you want to set up your matching:
sample-site.conf for our virtual hosting config:
server {
listen 80;
listen [::]:80;
server_name my.domain.com;
location / {
proxy_pass http://sample-site;
}
}
Based on how the proxy was set up, you'll need this file stored under your local conf.d folder which we mounted via the volumes declaration in the docker-compose file.
Last but not least, tell nginx to reload it's config.
docker exec nginx-proxy service nginx reload
These sequence of steps is the culmination of hours of pounding head-aches as I struggled with the ever painful 502 Bad Gateway error, and learning nginx for the first time, since most of my experience was with Apache.
This answer is to demonstrate how to kill the 502 Bad Gateway error that results from containers not being able to talk to one another.
I hope this answer saves someone out there hours of pain, since getting containers to talk to each other was really hard to figure out for some reason, despite it being what I expected to be an obvious use-case. But then again, me dumb. And please let me know how I can improve this approach.