Unable to replicate network alias

[joemsak]

Hi, I'm trying to dockerize cuprite for my app, and I started a blank rails app to figure out where I've gone wrong and I am reproducing the same issue in my blank rails app, which is that my network alias isn't working for the APP_HOST

The tests pass if I don't use a custom hostname/network alias, but we need that to work for subdomain-dependent specs

I started with the blog post https://evilmartians.com/chronicles/system-of-a-test-setting-up-end-to-end-rails-testing#dockerizing-system-tests and wound up here trying to figure things out piece by piece

# docker-compose.yml

volumes:
  volume_name:
    name: cuprite_test

services:
  app:
    environment:
      CHROME_URL: ${CHROME_URL:-http://chrome:3333}
      APP_HOST: ${APP_HOST:-app.mysite.local}
    build: .
    working_dir: /r
    command: bundle exec rails s
    volumes:
      - .:/r
      - ~/.npm:/root/.npm
      - .bundle:/usr/local/bundle
    ports:
      - 3001:3001
      - 3002:3002
    depends_on:
      - db
    networks:
      default:
        aliases:
          - app.mysite.local

  db:
   image: postgres
   volumes:
     - ./tmp/db:/var/lib/postgresql/data
   environment:
     POSTGRES_USER: postgresql
     POSTGRES_PASSWORD: password

  chrome:
    # Currently, Apple M1 is only supported in unnumbered "latest" versions.
    # See https://github.com/browserless/chrome/issues/1393
    image: browserless/chrome:latest
    ports:
      - "3333:3333"
    # Mount application source code to support file uploading
    # (otherwise Chrome won't be able to find files).
    # NOTE: Make sure you use absolute paths in `#attach_file`.
    volumes:
      - .:/app:cached
    environment:
      # By default, it uses 3000, which is typically used by Rails.
      PORT: 3333
      # Set connection timeout to avoid timeout exception during debugging
      # https://docs.browserless.io/docs/docker.html#connection-timeout
      CONNECTION_TIMEOUT: 600000

# spec/system/support/capybara_setup.rb

# Usually, especially when using Selenium, developers tend to increase the max wait time.
# With Cuprite, there is no need for that.
# We use a Capybara default value here explicitly.
Capybara.default_max_wait_time = 2

# Normalize whitespaces when using `has_text?` and similar matchers,
# i.e., ignore newlines, trailing spaces, etc.
# That makes tests less dependent on slightly UI changes.
Capybara.default_normalize_ws = true

# Where to store system tests artifacts (e.g. screenshots, downloaded files, etc.).
# It could be useful to be able to configure this path from the outside (e.g., on CI).
Capybara.save_path = ENV.fetch("CAPYBARA_ARTIFACTS", "./tmp/capybara")

Capybara.singleton_class.prepend(Module.new do
  attr_accessor :last_used_session

  def using_session(name, &block)
    self.last_used_session = name
    super
  ensure
    self.last_used_session = nil
  end
end)

Capybara.server_host = "0.0.0.0"
Capybara.server_port = 3002
# Use a hostname that could be resolved in the internal Docker network
Capybara.app_host = "http://#{ENV.fetch('APP_HOST', `hostname`.strip&.downcase || '0.0.0.0')}"

All the other system support files are exactly as you have them, except we don't use Webpacker

# spec/system/hello_world_spec.rb
require "system_helper"

RSpec.describe "Hello world" do
  scenario do
    visit root_path
    expect(page.body).to have_content("Hello cuprite world")

    # PASSES if not using custom hostname, but we need custom hostnames with subdomains
  end
end

# config/routes.rb

Rails.application.routes.draw do
  # Define your application routes per the DSL in https://guides.rubyonrails.org/routing.html

  # Reveal health status on /up that returns 200 if the app boots with no exceptions, otherwise 500.
  # Can be used by load balancers and uptime monitors to verify that the app is live.
  get "up" => "rails/health#show", as: :rails_health_check

  # Render dynamic PWA files from app/views/pwa/* (remember to link manifest in application.html.erb)
  # get "manifest" => "rails/pwa#manifest", as: :pwa_manifest
  # get "service-worker" => "rails/pwa#service_worker", as: :pwa_service_worker

  # Defines the root path route ("/")
  root "welcome#show"
end

Hello world 
     Failure/Error: visit root_path
     
     Ferrum::StatusError:
       Request to http://app.mysite.local:3002/ failed (net::ERR_NAME_NOT_RESOLVED)
     
     [Screenshot Image]: tmp/capybara/failures_r_spec_example_groups_hello_world_example_at___spec_system_hello_world_spec_rb_4_5.png

     
     # /usr/local/bundle/gems/ferrum-0.15/lib/ferrum/page.rb:111:in 'Ferrum::Page#go_to'
     # /usr/local/bundle/gems/cuprite-0.15.1/lib/capybara/cuprite/browser.rb:75:in 'Capybara::Cuprite::Browser#visit'
     # /usr/local/bundle/gems/cuprite-0.15.1/lib/capybara/cuprite/driver.rb:57:in 'Capybara::Cuprite::Driver#visit'
     # /usr/local/bundle/gems/capybara-3.40.0/lib/capybara/session.rb:281:in 'Capybara::Session#visit'
     # /usr/local/bundle/gems/capybara-3.40.0/lib/capybara/dsl.rb:52:in 'Method#call'
     # /usr/local/bundle/gems/capybara-3.40.0/lib/capybara/dsl.rb:52:in 'Capybara::DSL#visit'
     # ./spec/system/hello_world_spec.rb:5:in 'block (2 levels) in <main>'
     # ./spec/system/support/better_rails_system_tests.rb:25:in 'block (2 levels) in <main>'

Finished in 0.91628 seconds (files took 0.73827 seconds to load)
4 examples, 1 failure, 2 pending

The generated spec/requests/welcome_spec.rb that came with rails g controller welcome show is passing (200 OK)

I added the text Hello cuprite world to the welcome/show.html.erb file and it was passing before I tried using a custom host name. We need the custom hostname working because we have subdomain-dependent specs.

commands:

docker compose up -d chrome
docker compose run --it app bash
bundle exec rspec

Here is the full source in case it helps:

https://github.com/joemsak/cuprite-test

Any help or insight offered would be greatly appreciated, thank you!

[joemsak]

Just tried adding my.db.alias to the db: service and it worked fine from the rails app:

docker compose run -it app bash
root@06870aab6687:/r# ping -c 1 my.db.alias
PING my.db.alias (172.19.0.2) 56(84) bytes of data.
64 bytes from cuprite-test-db-1.cuprite-test_default (172.19.0.2): icmp_seq=1 ttl=64 time=0.054 ms

--- my.db.alias ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.054/0.054/0.054/0.000 ms
root@06870aab6687:/r#

[joemsak]

And from the chrome service:

# With iputils-ping installed
docker compose up -d app

✗ docker compose run -it chrome bash                  
WARN[0000] Found orphan containers ([cuprite-test-db-run-40211c84f57f cuprite-test-db-run-d983a565f118 cuprite-test-chrome-run-5fe65566f954 cuprite-test-chrome-run-6a73b8493786 cuprite-test-app-run-369fcb7c85dc cuprite-test-app-run-a4f76dedfc03 cuprite-test-app-run-5a71848a6e1d cuprite-test-app-run-58155919fe48 cuprite-test-app-run-d30cc3e9b114 cuprite-test-app-run-a727d0e6026a cuprite-test-app-run-3e431a2f61bc cuprite-test-app-run-51acfdd1fa9e cuprite-test-app-run-329857fc9895 cuprite-test-app-run-8f5e0a0e3daf cuprite-test-app-run-463d5c08ef6d cuprite-test-app-run-fdda3cb95910 cuprite-test-app-run-3078efc34af6 cuprite-test-app-run-063435d621b0 cuprite-test-app-run-94a2a48c7a95 cuprite-test-app-run-719d7dff28bf]) for this project. If you removed or renamed this service in your compose file, you can run this command with the --remove-orphans flag to clean it up. 
root@029f00dfd611:/usr/src/app# ping app.mysite.local
PING app.mysite.local (172.19.0.4) 56(84) bytes of data.
64 bytes from cuprite-test-app-1.cuprite-test_default (172.19.0.4): icmp_seq=1 ttl=64 time=0.084 ms
64 bytes from cuprite-test-app-1.cuprite-test_default (172.19.0.4): icmp_seq=2 ttl=64 time=0.059 ms
^C
--- app.mysite.local ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1058ms
rtt min/avg/max/mdev = 0.059/0.071/0.084/0.012 ms
root@029f00dfd611:/usr/src/app# 

So it can ping...