Can't launch Selenium + PhantomJS/GhostDriver as Child processes

Question

I've got a Node script that I want to use the child_process module with to get a Selenium server running with PhantomJS's GhostDriver.

I've required the module: Child = require "child_process"

And here's how I'm trying to start the server and attach GD to it (in Coffeescript):

@Selenium = new Child.exec "java -jar selenium/selenium-server-standalone-2.44.0.jar -role hub -port 4444", (error, stdout, stderr) =>
    console.log stdout
    console.log error if error
@PhantomJS = new Child.exec "phantomjs --webdriver=8080 --webdriver-selenium-grid-hub=http://127.0.0.1:4444", (error, stdout, stderr) =>
    console.log stdout
    console.log error if error

The stdout for @PhantomJS is this:

PhantomJS is launching GhostDriver...
[ERROR - 2014-12-10T18:51:27.587Z] GhostDriver - main.fail - {"message":"Could not start Ghost Driver","line":82,"sourceId":4469911104,"sourceURL":":/ghostdriver/main.js","stack":"Error: Could not start Ghost Driver\n    at :/ghostdriver/main.js:82","stackArray":[{"sourceURL":":/ghostdriver/main.js","line":82}]}

Additionally, I get this error from that command: {"killed": false, "code": 1, "signal": null}

Some notes:

• The Selenium jar file is in fact located at selenium/selenium-server-standalone-2.44.0.jar
• I've tried npm updateing just to see if that would make a difference
• It occurred to me that something else might be running on port 4444, so I went ahead and ran "PORT_NUMBER=4444 | lsof -i tcp:${PORT_NUMBER} | awk 'NR!=1 {print $2}' | xargs kill" to no avail
• I've tried installing PhantomJS from the source as per this suggestion to the same error
• If I run these commands separately, outside of the script, it all works fine

Answer 1

In case anyone else has this issue, we solved it using daemon to run the child process in the background so that the terminal is free to run other commands/scripts.

Note: you will need to install the daemon module from NPM: npm install daemon --save-dev
(it has tests + decent usage stats and does what you need/expect)

Create a file called selenium_child_process.js and paste the following code:

console.log('Starting Selenium ...');
require('daemon')(); // this will run everything after this line in a daemon:
const exec = require('child_process').exec;
// note: your path to the selenium.jar may be different!
exec('java -jar ./bin/selenium.jar', (error, stdout, stderr) => {
  if (error) {
    console.error(`exec error: ${error}`);
    return;
  }
  if (stdout) {
    console.log(`> ${stdout}`); 
  }
  if (stderr) {
    console.log(`>> ${stderr}`); // handle errors in your preferred way.
  }
});

Then run the file with node selenium_child_process.js (in your terminal)

You now have selenium running as a child (background) process on TCP Port 4444.

---

If you want to shut down the Selenium server, you will need to kill the process. We use the following command:

lsof -n -iTCP:4444 -sTCP:LISTEN -n -l -P | grep 'LISTEN' | awk '{print $2}' | xargs kill -9

If you get stuck we're happy to help!