Logs are not just used when things go wrong. They also help you keep track of what is going on within your app. We will look at how you can add helpful messages throughout your codebase and leave them there, even in production! We will cover common logging strategies, log aggregation, and how to efficiently work with your logs to get the data back out. We will also look at Graphite, which can help work out what actually happened by correlating logs with peaks/drops in other systems.