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dockernginxdocker-composenetwork-programmingwindows-server
kalvis
kalvis

Reputation: 570

Windows Server Docker container cannot connect to proxy container after web server restart

I have 2 Windows Server Docker containers deployed with Docker Compose. One container runs a reverse proxy server and the other runs a web server. The web server serves a simple index.html page. Both are running Nginx.

When run, everything works as expected. I can access content via the proxy. But if I restart the web server I get a bad gateway error. I then need to restart the proxy to get it working again.

How do I get this working without the need to restart the proxy?

Docker-compose:

version: '3'

services: 
    web:
        build:
            context: ./web
            dockerfile: ./dockerfile
    proxy:
        build:
            context: ./proxy
            dockerfile: ./dockerfile
        ports:
            - "8089:80"

Proxy Dockerfile:

FROM sixeyed/nginx:windowsservercore

COPY nginx.conf C:/nginx/conf
CMD C:\nginx\nginx.exe

Proxy nginx.config:

events {
}
http {
    server {
        listen       80;
        server_name  localhost;

        location / {
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_pass http://web:80/;
        }
    }
}

Web Dockerfile:

FROM sixeyed/nginx:windowsservercore

COPY nginx.conf C:/nginx/conf
COPY index.html C:/nginx/html/index.html

CMD C:\nginx\nginx.exe

Web nginx.config:

events {
}

http {
    server {
        listen       80;
        server_name  localhost;

        location / {
            root   html;
            index  index.html index.htm;
        }
    }
}

Upvotes: 5

Views: 927

Answers (2)

VDR
VDR

Reputation: 2863

Nginx is caching the resolved DNS IP of web container. You can configure Nginx to invalidate DNS cache(use different TTL than the one set on DNS record) by adding resolver 127.0.0.11 valid=1s to the proxy nginx.config file.

Info on Nginx resolver: http://nginx.org/en/docs/http/ngx_http_core_module.html#resolver

Upvotes: 0

pygeek
pygeek

Reputation: 7414

Problem

web reference in the proxy container’s nginx.conf is referring to the up of the container that is referenced when nginx server was started. When web restarts the old ip becomes unavailable and a new ip is used, the container web reference is then updated, however nginx server is still referencing the old ip since configuration changes are only applied on start/restart.

Solution

You need to restart the nginx proxy server—not necessarily the container—when your web container is replaced. This can be done by using docker-gen to monitor metadata regarding containers and restart nginx when a change is detected. Luckily nginx-proxy, does this for you. nginx-proxy is well maintained, and an alternative to you having to maintain this business logic yourself.

References

Nginx Proxy: https://github.com/nginx-proxy/nginx-proxy

Upvotes: 2

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