Debugging your app is what you do when the logic doesn't work as expected and you're trying to track down what's going wrong. You don't debug in production, so you need your app to record its behavior in order to help you trace any problems that occur.
Instrumentation is often neglected, but it should be a crucial component of your development, as it's the best way to understand the health and activity of your app in production. Running your app in Docker provides new opportunities for centralized logging and instrumentation, so you can get a consistent view across the different parts of your application even if they use different languages and platforms.