title: What is the correct docker-compose yml to set maxSessions & maxInstances for selenium hub node-chrome
body: <p>As a newbie to docker-selenium, yml and docker compose, can someone please advise me how to correctly set the max hub sessions and node essions/instances in docker compose? I'm currently using this yml:-</p>
  
  <pre><code>version: '2'
  services:
    chrome:
      image: selenium/node-chrome:3.10.0-argon
      volumes:
         - /dev/shm:/dev/shm
      depends_on:
         - hub
      environment:
         - NODE_MAX_INSTANCES=10
         - NODE_MAX_SESSION=10
         - HUB_HOST=hub
  
    hub:
      image: selenium/hub:3.10.0-argon
      ports:
        - "4444:4444"
      environment:
        - GRID_MAX_SESSION=10
  </code></pre>
  
  <p>, which is a slight modification on the vanilla example from <a href="https://github.com/SeleniumHQ/docker-selenium/blob/master/README.md/" rel="noreferrer">docker-selenium readme</a> I would expect to be able to set the number of sessions and instances correctly in hub and node docker instances. </p>
  
  <p>However, when I inspect the containers, the default settings have been used:-</p>
  
  <pre><code> "NODE_MAX_INSTANCES=1",
   "NODE_MAX_SESSION=1",
  </code></pre>
  
  <p>on the node and :-</p>
  
  <pre><code> "GRID_MAX_SESSION=5",
  </code></pre>
  
  <p>on the hub. How can I fix this? I don't really want to have to spin up a hub for every 5 chromedriver instances I want to run. I should be able to squeeze in a few chromedriver instances per node, and have maybe 50+ instances per hub.</p>