CODEWITHSUNDEEP
dockernginxamazon-ec2proxy
RonZhang724
RonZhang724

Reputation: 575

Docker 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:

enter image description here

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

Upvotes: 4

Views: 10175

Answers (1)

TJ Zimmerman
TJ Zimmerman

Reputation: 3484

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.

Upvotes: 9

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