When we create our programs, we usually don’t anticipate anything will go wrong. And it won’t during development and testing. But in production, there is always someone who does something unexpected, and then the code fails. When running in development, you can easily step through your code and see what happens, but in production you are not allowed to do this. How great would it be if you could see what was happening in the production environment? But logging every step takes up a lot of the performance. Installing debuggable code in production just to see what’s going on is usually a no-go. By instrumenting your code, you can get the information you need by “flipping a switch.” This session shows how you can use the (extended) Open Source Logger framework to accomplish this.