logging.md

• Logging
  • Selenium Process
  • Debug Logs for Selenium Standalone Process

Logging

Selenium Process

By default, Selenium sends logging messages to stderr.

The selenium-standalone cli tool (selenium-standalone start) will output the logging messages to your process.stderr. So you do see them in the console.

If you are using the programmatic API, you can retrieve the stderr messages by doing this:

const selenium = require('selenium-standalone');
selenium.start(function(err, child) {
  child.stderr.on('data', function(data){
    console.log(data.toString());
  });
});

You can also forward the stderr to your process.stderr like the cli does:

const selenium = require('selenium-standalone');
selenium.start({
  spawnOptions: {
      stdio: 'inherit'
  }
}, function(err, child) {
  // child.stderr now sent to your `process.stderr`
});

Debug Logs for Selenium Standalone Process

At times you may need to get debug logs for what selenium-standalone is doing. In your environment variables set DEBUG=selenium-standalone:*. This will enable extra log statements to be shown in stderr.

Example:

$ DEBUG=selenium-standalone:* selenium-standalone install --drivers.chrome.version=87.0.4280.20
  selenium-standalone:env-details Platform: darwin 19.6.0 +0ms
  selenium-standalone:env-details Architecture: x64 +1ms
  selenium-standalone:env-details Node.js: v12.18.4 +0ms
  selenium-standalone:env-details Package Version: 6.21.0 +0ms
  selenium-standalone:cli Started via CLI with:  [ '/usr/local/bin/node',
  '/tmp/selenium-standalone/bin/selenium-standalone',
  'install',
  '--drivers.chrome.version=87.0.4280.20' ]
  ...