Selenium not able to access website hosted in another Docker container - docker

Question

Any docker, Selenium expert, I would appreciate your help!
I have a web application(LNMP), and I use docker at my local as dev environment.
Now, I am trying to add an additional Selenium container so I can use it for automated testing (https://hub.docker.com/r/selenium/standalone-chrome-debug).
I couldn't figure out how to set up the connection from Selenium container to my application container(Nginx), because the website is not published.
When I develop at my local, I use a test domain, and I connect to the website by editing the host file at my local.
e.g.
127.0.0.1 website.test
I have tried adding the Selenium container in the yaml file, looks like it was successful, and I am able to use a VNC client from the host to connect to the container.
But I always got Connection Refused when I try to access the website from the Selenium browser. Looks like the DNS works otherwise Chrome would give me a DNS error rather than connection refuse.
My yaml file looks like, as you can see, I added a Selenium container(browser_chrome) and a network(testing). app is the original Nginx container.
networks:
testing:
version: "3"
services:
browser_chrome:
image: selenium/standalone-chrome-debug:3.8.1
ports:
- "5900:5900"
networks:
- testing
app:
networks:
testing:
aliases:
- "website.test"
This is the original docker file without the Selenium setup, https://github.com/markshust/docker-magento/blob/master/compose/docker-compose.yml, basically, I added the Selenium container(browser_chrome) and the network(testing) to connect them.
I only know the basic stuff of docker, so any help would be appreciated!
:)

Answer 1

First of all you don't have to create static network to work with this and leave docker to fit it itself = less problems in future (at least that's my opinion). By not specifying docker network in compose file you leave docker to create network called default (container point of view), from host point of view called <stack-name>_default
Second thing you have to understand is how networking and connection between two containers in stack works -> Here for connection between containers you have to use service names (in your case app) as docker automatically creates DNS records for it
Here is simple compose file to test validity of above:
version: "3"
services:
server:
image: containous/whoami
client:
image: appropriate/curl
command: "curl -vvv http://server"
And output from console and service logs
$ docker stack deploy -c docker-compose.yml test
Creating network test_default
Creating service test_server
Creating service test_client
$ docker service logs -f test_client
test_client.1.fv8dq5b80dkk#... | * Rebuilt URL to: http://server/
test_client.1.fv8dq5b80dkk#... | % Total % Received % Xferd Average Speed Time Time Time Current
test_client.1.fv8dq5b80dkk#... | Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0* Trying 10.0.5.2...
test_client.1.fv8dq5b80dkk#... | * TCP_NODELAY set
test_client.1.fv8dq5b80dkk#... | * Connected to server (10.0.5.2) port 80 (#0)
test_client.1.fv8dq5b80dkk#... | > GET / HTTP/1.1
test_client.1.fv8dq5b80dkk#... | > Host: server
test_client.1.fv8dq5b80dkk#... | > User-Agent: curl/7.59.0
test_client.1.fv8dq5b80dkk#... | > Accept: */*
test_client.1.fv8dq5b80dkk#... | >
test_client.1.fv8dq5b80dkk#... | < HTTP/1.1 200 OK
test_client.1.fv8dq5b80dkk#... | < Date: Tue, 01 Jun 2021 09:54:21 GMT
test_client.1.fv8dq5b80dkk#... | < Content-Length: 162
test_client.1.fv8dq5b80dkk#... | < Content-Type: text/plain; charset=utf-8
test_client.1.fv8dq5b80dkk#... | <
test_client.1.fv8dq5b80dkk#... | { [162 bytes data]
test_client.1.fv8dq5b80dkk#... | Hostname: 7d91b392ac0a
test_client.1.fv8dq5b80dkk#... | IP: 127.0.0.1
test_client.1.fv8dq5b80dkk#... | IP: 10.0.5.3
test_client.1.fv8dq5b80dkk#... | IP: 172.18.0.4
test_client.1.fv8dq5b80dkk#... | RemoteAddr: 10.0.5.4:45600
test_client.1.fv8dq5b80dkk#... | GET / HTTP/1.1
test_client.1.fv8dq5b80dkk#... | Host: server
test_client.1.fv8dq5b80dkk#... | User-Agent: curl/7.59.0
test_client.1.fv8dq5b80dkk#... | Accept: */*
test_client.1.fv8dq5b80dkk#... |
100 162 100 162 0 0 23142 0 --:--:-- --:--:-- --:--:-- 27000
test_client.1.fv8dq5b80dkk#... | * Connection #0 to host server left intact