Setup Heroku Review App with Cloudflare DNS

app.json

{
  "environments": {
    "review": {
      "scripts": {
        "postdeploy": "bundle exec rake heroku:review_app_setup",
        "pr-predestroy": "bundle exec rake heroku:review_app_predestroy"
      }
    }
  }
}

heroku.rake

namespace :heroku do
  desc 'Setup Cloudflare DNS record for Heroku Review App'
  task :review_app_setup do
    require 'cloudflare'
    require 'platform-api'
    require 'octokit'

    custom_domain = 'example.com'.freeze

    # Heroku app names are default "<name>-pr-<pull request ID>"
    heroku_app_name = ENV['HEROKU_APP_NAME']
    email = ENV['CLOUDFLARE_EMAIL']
    key = ENV['CLOUDFLARE_KEY']
    pr_number = ENV['HEROKU_PR_NUMBER']

    subdomain = "app-pr-#{pr_number}"
    wild_subdomain = ["*", subdomain].join('.')

    # Configure custom domain in Heroku
    heroku_client = PlatformAPI.connect_oauth ENV['HEROKU_PLATFORM_TOKEN']
    hostname = [subdomain, custom_domain].join('.')
    heroku_client.domain.create(heroku_app_name, hostname: hostname, sni_endpoint: nil)
    heroku_domain = heroku_client.domain.info(heroku_app_name, hostname)["cname"]

    # Also add wildcard (*.) subdomain
    wild_hostname = [wild_subdomain, custom_domain].join('.')
    heroku_client.domain.create(heroku_app_name, hostname: wild_hostname, sni_endpoint: nil)
    wild_heroku_domain = heroku_client.domain.info(heroku_app_name, wild_hostname)["cname"]

    Cloudflare.connect(key: key, email: email) do |connection|
      # Get a specific zone:
      zone = connection.zones.find_by_id(ENV['CLOUDFLARE_ZONE_ID'])
      
      # Search existing records
      dns_record = zone.dns_records.find_by_name(subdomain)
      wild_dns_record = zone.dns_records.find_by_name(wild_subdomain)

      # Add a DNS record. Here we add an A record for `batman.example.com`:
      if dns_record == nil
        # Create DNS record in Cloudflare
        zone.dns_records.create('CNAME', subdomain, heroku_domain, proxied: false)
      end

      if wild_dns_record == nil
        zone.dns_records.create('CNAME', wild_subdomain, wild_heroku_domain, proxied: false)
      end
    end

    # Add PR comment with deployment URL
    github_client = Octokit::Client.new(:access_token => ENV['GITHUB_TOKEN'])
    github_client.add_comment(ENV['GITHUB_REPO'], pr_number.to_i, "The review app has been deployed here: <a href='http://#{hostname}' target='_blank'>#{hostname}</a>")
  end

  desc 'Remove DNS Record from Cloudflare for Heroku Review App upon deletion'
  task :review_app_predestroy do
    require 'cloudflare'

    # Cleanup subdomain DNS record for Heroku review app
    custom_domain = 'example.com'.freeze
    heroku_app_name = ENV['HEROKU_APP_NAME']
    email = ENV['CLOUDFLARE_EMAIL']
    key = ENV['CLOUDFLARE_KEY']
    pr_number = ENV['HEROKU_PR_NUMBER']

    subdomain = "app-pr-#{pr_number}"
    wild_subdomain = ["*", subdomain].join('.')

    Cloudflare.connect(key: key, email: email) do |connection|
      # Get a specific zone:
      zone = connection.zones.find_by_id(ENV['CLOUDFLARE_ZONE_ID'])

      dns_record = zone.dns_records.find_by_name([subdomain, custom_domain].join('.'))
      wild_dns_record = zone.dns_records.find_by_name([wild_subdomain, custom_domain].join('.'))

      dns_record.delete if dns_record != nil
      wild_dns_record.delete if wild_dns_record != nil
    end
  end
end

@mfts your script works after adding sni param. I just added acme, because we needed https. But without https, your script in working mode:)