Is Dockerfile Config Independent of nginx Server Blocks?

Question

I’m working on setting up my development/deployment pipeline for my ubuntu Droplet. I used the one-click Docker Droplet and have followed the guides Install nginx, Initial Server Setup, and Secure nginx.

Where I get lost is how the Docker container and nginx/nginx server block are tied together. I have my image on Docker Hub, building on changes to my GitHub repo. That works great. I can pull the images onto my server, and run them, but I don’t know how to access them or set them up with a server block.

For example, this guide says I should be able to run a container, map it to port 8080, and access it via http://my-ip:8080 but that doesn’t work for me. Thinking 8080 probably isn’t exposed by default, I allowed it in ufw, restarted ufw, and tried again, but no luck. Trying this, and trying to figure out why it doesn’t work, and if it even should, has left me more confused.

Any input that could help clear up this last piece of the puzzle appreciated.

Thanks!

Answer 1

bobbyiliev February 9, 2021

Hi there,

Can you share the command that you use to start your containers here?

Port 8080 is just an example for the guide, if you bind your containers on different ports, then you would need to use that specific port in your reverse proxy config.

Feel free to share the output of the docker ps command here.

Regards,
Bobby

Reply Report

TurboLaser February 10, 2021
Hi Bobby, thanks for your reply.

I have used

docker run -dit --name container-1 -p 8080:80 httpd:2.4

docker ps currently shows

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 5ba1f6d99380 httpd:2.4 "httpd-foreground" 17 hours ago Up 17 hours 0.0.0.0:8080->80/tcp container-1

If I run curl my-ip:8080 I see:
<html><body><h1>It works!</h1></body></html>

However, when I try to access my-ip:8080 in a browser, it doesn’t load.
Reply Report
- bobbyiliev February 10, 2021
  
  Hi there @TurboLaser,
  
  Yes indeed this looks like your firewall might be blocking the connections. Do you get the same result after opening port 8080?
  
  sudo ufw allow 8080
  
  Also, do you have any other firewalls enabled besides ufw?
  
  Regards,
  Bobby
  
  Reply Report
  
  TurboLaser February 10, 2021
  
  Yes, same result after allowing 8080 through ufw (and restarting ufw).
  
  I don’t believe I have any other firewalls enabled.
  
  Reply Report
  
  bobbyiliev February 11, 2021
  
  Hi there,
  
  What I could suggest is checking if the container is actually listening on that port with the following command:
  
  netstat -plant | grep 8080
  
  Also, can you share your Nginx server block here? If you have Nginx configured as a reverse proxy, you should be able to access the container on port 80 directly.
  
  Regards,
  Bobby
  
  Reply Report
  
  TurboLaser February 16, 2021
  
  Hi @bobbyiliev - I meant to reply to you but added an answer instead.
  
  My server is up and running, and I seem to have no issues with the proxy_pass setup.
  
  I would still be curious about when 8080 would be publicly accessible, and when it wouldn’t, as in my tests allowing it through ufw didn’t seem to make a difference. Just to further my understanding :)
  
  Reply Report
  
  bobbyiliev February 16, 2021
  
  Hi there @TurboLaser,
  
  Yep, as the container is binding on 0.0.0.0:8080 this means that by visiting your_ip:8080 you should be able to access it publicly.
  
  If this is not the case, then it is mostlikely due to a firewall on the server or if you have a managed firewall from DigitalOcean. Another thing that could be preventing you from accessing the service directly on port 8080 is a local firewall on your home/office network.
  
  Hope that this helps!
  Regards,
  Bobby
  
  Reply Report

Answer 2

TurboLaser February 10, 2021
Hi Bobby, thanks for your reply.

I have used

docker run -dit --name container-1 -p 8080:80 httpd:2.4

docker ps currently shows

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 5ba1f6d99380 httpd:2.4 "httpd-foreground" 17 hours ago Up 17 hours 0.0.0.0:8080->80/tcp container-1

If I run curl my-ip:8080 I see:
<html><body><h1>It works!</h1></body></html>

However, when I try to access my-ip:8080 in a browser, it doesn’t load.
Reply Report
- bobbyiliev February 10, 2021
  
  Hi there @TurboLaser,
  
  Yes indeed this looks like your firewall might be blocking the connections. Do you get the same result after opening port 8080?
  
  sudo ufw allow 8080
  
  Also, do you have any other firewalls enabled besides ufw?
  
  Regards,
  Bobby
  
  Reply Report
  
  TurboLaser February 10, 2021
  
  Yes, same result after allowing 8080 through ufw (and restarting ufw).
  
  I don’t believe I have any other firewalls enabled.
  
  Reply Report
  
  bobbyiliev February 11, 2021
  
  Hi there,
  
  What I could suggest is checking if the container is actually listening on that port with the following command:
  
  netstat -plant | grep 8080
  
  Also, can you share your Nginx server block here? If you have Nginx configured as a reverse proxy, you should be able to access the container on port 80 directly.
  
  Regards,
  Bobby
  
  Reply Report
  
  TurboLaser February 16, 2021
  
  Hi @bobbyiliev - I meant to reply to you but added an answer instead.
  
  My server is up and running, and I seem to have no issues with the proxy_pass setup.
  
  I would still be curious about when 8080 would be publicly accessible, and when it wouldn’t, as in my tests allowing it through ufw didn’t seem to make a difference. Just to further my understanding :)
  
  Reply Report
  
  bobbyiliev February 16, 2021
  
  Hi there @TurboLaser,
  
  Yep, as the container is binding on 0.0.0.0:8080 this means that by visiting your_ip:8080 you should be able to access it publicly.
  
  If this is not the case, then it is mostlikely due to a firewall on the server or if you have a managed firewall from DigitalOcean. Another thing that could be preventing you from accessing the service directly on port 8080 is a local firewall on your home/office network.
  
  Hope that this helps!
  Regards,
  Bobby
  
  Reply Report

Answer 3

TurboLaser February 15, 2021

Yes, I can access containers on port 80 directly, however I was confused that I couldn’t access them over 8080 as it might have indicated a problem with my server setup. One of the per-requisites in your guide is setting up nginx with ufw.

netstat -plant | grep 8080

returns

tcp        0      0 0.0.0.0:8080            0.0.0.0:*               LISTEN      81965/docker-proxy

My server block:

server {

        root /var/www/myurl.com/html;
        #replaced folder with {server-block}
        index index.html index.htm index.nginx-debian.html;

        server_name myurl.com www.myurl.com;

        location / {
               # try_files $uri $uri/ =404;
                proxy_pass  http://localhost:8080;
        }

    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/myurl.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/myurl.com/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot




}
server {
    if ($host = www.myurl.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


    if ($host = myurl.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


        listen 80;
        listen [::]:80;

        server_name myurl.com www.myurl.com;


    return 404; # managed by Certbot




}

edited by MattIPv4

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