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ViewsDocker Nginx: host not found in upstream
I have my docker app running in the aws EC2 instance, and I am currently trying to map the app to the external IP address using Nginx. Here is a snap shot of the containers that I have running:
My test-app is a fairly simple app that displays a static html website. And I deployed it using the following command:
docker run -d --name=test-app test-app
The nginx-proxy has the following proxy.conf
server {
listen 80;
location / {
proxy_pass http://test-app;
}
}
Here is the Dockerfile for the nginx proxy:
FROM nginx:alpine
RUN rm /etc/nginx/conf.d/*
COPY proxy.conf /etc/nginx/conf.d/
nginx-proxy is run using the following command:
docker run -d -p 80:80 --name=nginx-proxy nginx-proxy
However, the nginx container never runs, and here the error log I get
2020/03/27 15:55:19 [emerg] 1#1: host not found in upstream "test-app" in /etc/nginx/conf.d/proxy.conf:5
nginx: [emerg] host not found in upstream "test-app" in /etc/nginx/conf.d/proxy.conf:5
1 answers
Answer question0
While your two containers are both running and you have properly exposed the ports required for the NGINX container. You have not exposed any ports for the test-app container. The NGINX container has no way of talking to it. Exposing ports directly with docker run would likely defeat the point of using a reverse proxy in your situation. So instead, what you should do in this situation is create a Network for both of your Docker containers and then add them to it. Then they will be able to communicate with one-another over a bridge. For example:
docker network create example
docker run -d --network=example --name=test-app test-app
docker run -d -p 80:80 --network=example --name=nginx-proxy nginx-proxy
Now that you have both of your pods on the same network, Docker will enable DNS-based service discovery between them by container name and you will be able to resolve them from each other. You can test connectivity like so: docker exec -it nginx-proxy ping test-app. Well, that is provided ping is installed in that Docker container.