parallel_chrome.rb

require 'selenium-webdriver'

chrome_service = Selenium::WebDriver::Chrome::Service.default_service
chrome_service.start

pids = []

8.times do |n|
  pids << fork do
    driver = Selenium::WebDriver.for :chrome, :url => chrome_service.uri
    driver.get 'http://google.com'
    
    driver.first(name: 'q').send_keys("proc #{n}")
    driver.quit
  end
end

pids.each { |pid| Process.waitpid pid }
chrome_service.stop