Node http-proxy in Docker container

Question

I have the following code that works great in my local environment. However, when I try to run the same code from a Docker container (via Boot2Docker), I simply cannot get to https://[boot2docker_ip]:4000

I tried updating the target value in the code below with all these options but none of them seemed to do the trick:

target: 'http://localhost:3000',
target: 'http://0.0.0.0:3000',
target: 'http://127.0.0.1:3000',
target: 'http://<boot2docker_ip>:3000',

var fs = require('fs');    

require('http-proxy').createProxyServer({
  ssl: {
    key: fs.readFileSync(__dirname + '/certs/ssl.key', 'utf8'),
    cert: fs.readFileSync(__dirname + '/certs/ssl.crt', 'utf8')
  },
  target: 'http://localhost:3000',
  ws: true,
  xfwd: true
}).listen(4000);

I am using the node-http-proxy package from https://github.com/nodejitsu/node-http-proxy

Edit

Here is a Git repo to try out this behavior; I have checked in fake SSL for simplicity.

Dockerfile:

FROM readytalk/nodejs

ADD ./src /app
ADD ./ssl-proxy /proxy

COPY ./run.sh /run.sh
RUN chmod +x /run.sh

EXPOSE 3000
EXPOSE 4000

ENTRYPOINT ["/run.sh"]

run.sh:

#!/bin/sh

/nodejs/bin/node /app/main.js; /nodejs/bin/node /proxy/main.js

Walkway

Where is the service that's listening on port 3000 running? On your host machine, or inside another Docker container? – Demy

Inside the same docker container. I start this proxy first and then that service on port 3000 – Walkway

I see. Your Dockerfile and/or the docker run command that you're using to start the container might be useful. – Demy

Check to edit. Here is the repo for you to try out: github.com/munjalpatel/node-http-proxy-test – Walkway

Alright! I edited your question to include the code in question (typically, link-only questions and answers are discouraged on SO because links tend to become invalid) and drew up an answer below. Let me know if it helps! – Demy

Answer 1

I just had a look at your Dockerfile and especially the run.sh script that you use. This line is from your run.sh script:

/nodejs/bin/node /app/main.js; /nodejs/bin/node /proxy/main.js

What's important to know here is that each of these commands start a long-running server process that (theoretically) runs forever. This means that the second process (/proxy/main.js) will never start because the shell will wait for the first process to finish.

This means that you cannot access your proxy server because it never starts.

Basically there are two solutions to this that I could think of. Please note that the idiomatic "Docker way" is to run one process per container only, though.

1. I'd recommend running your application and the proxy server in two separate containers. You can link those two containers together:

   docker run --name app -p 3000 <your-image> /nodejs/bin/node /app/main.js
   docker run --name proxy -l app:app -p 4000:4000 <your-image> /nodejs/bin/node /proxy/main.js
   

   The flag -l app:app will cause the app container to be available with the hostname app in your proxy container (this is done by creating a /etc/hosts entry in the container). This means, inside the proxy container, you can then use http://app:3000 to access your upstream application port.

2. An alternative solution would be to use a process manager tool like Supervisord to manage several long-running processes in your container in parallel. There's a good article on that in the documentation. It basically boils down to the following:

   1. Install supervisord (apt-get install supervisor in Ubuntu)

   2. Create a configuration file (typically in /etc/supervisor/conf.d/yourapplication.conf) in which you configure all services that you need to run:

      [supervisord]
      nodaemon=true
      
      [program:application]
      command=/nodejs/bin/node /app/main.js
      
      [program:proxy]
      command=/nodejs/bin/node /proxy/main.js
      

   3. Then use supervisord as your start command, for example by using CMD ["/usr/bin/supervisord"] in your Dockerfile.

   In this case, both your processes are running in the same container and you can use http://localhost:3000 to access your upstream application.

Demy