Linking a docker container a subdirectory of another one - docker

Question

I am trying to setup multiple docker containers that can be accessed through one main container.
For example:
http://localhost:80 is the main container
http://localhost:80/site1 is a separate container
http://localhost:80/site2 is a separate container again
I know that the --link flag has been deprecated and the new way of doing things is by using the --network flag.
When I use the --link (for testing) I see an entry of the container I am linking to in the hosts file. That is where I am stuck.
So I would like to set the above scenario up using the docker --networking option.
Usage case: /Site1 might be the admin area or member to a website, but I would like to have them in separate containers so I can maintain them easier.
The containers are apache2 based, but if possible would like to refrain from editing any config files (but I can if I need to)
How would I go about that?

Answer 1

As far as I know there is no way that docker routes HTTP requests to one or the other container. You can only map a port from your host to one container.
What you will need is to run a reverse proxy (e.g. nginx) as your main container that then routes the request to the appropriate container.
Here an example how to set it up
site1/Dockerfile
FROM node:6.11
WORKDIR /site1
COPY site1.js .
CMD node site1.js
EXPOSE 80
site1/site1.js
var http = require("http");
http.createServer(function (request, response) {
response.writeHead(200, {'Content-Type': 'text/plain'});
response.end('Hello World 1\n');
}).listen(80);
site2/Dockerfile
FROM node:6.11
WORKDIR /site2
COPY site2.js .
CMD node site2.js
EXPOSE 80
site2/site2.js
var http = require("http");
http.createServer(function (request, response) {
response.writeHead(200, {'Content-Type': 'text/plain'});
response.end('Hello World 2\n');
}).listen(80);
node-proxy/default.conf
server {
listen 80;
# ~* makes the /site1 case insensitive
location ~* /site1 {
# Nginx can access the container by the service name
# provided in the docker-compose.yml file.
proxy_pass http://node-site1;
}
location ~* /site2 {
proxy_pass http://node-site2;
}
# Anything that didn't match the patterns above goes here
location / {
# proxy_pass http://some other container
return 500;
}
}
docker-compose.yml
version: "3"
services:
# reverse proxy
node-proxy:
image: nginx
restart : always
# maps config file into the proxy container
volumes:
- ./node-proxy/default.conf:/etc/nginx/conf.d/default.conf
ports:
- 80:80
links:
- node-site1
- node-site2
# first site
node-site1:
build: ./site1
restart: always
# second site
node-site2:
build: ./site2
restart: always
To start the reverse proxy and both sites enter in the root of this folder docker-compose up -d and check with docker ps -a that all docker containers are running.
Afterwards you can access this two sites with http://localhost/site1 and http://localhost/site2
Explanation
The folder site1 and site2 contains a small webserver build with nodejs. Both of them are listening on port 80. "node-proxy" contains the configuration file that tells nginx when to return which site.
Here are some links
docker-compose: https://docs.docker.com/compose/overview/
nginx reverse proxy: https://www.nginx.com/resources/admin-guide/reverse-proxy/

Answer 2

You should use volumes so you will set it in docker-compose.yml like this
version: '3.2'
services:
container1:
volumes:
- shared-files:/directory/files
container2:
volumes:
- shared-files:/directory/files
container3:
volumes:
- shared-files:/directory/files
volumes:
shared-files: