The Prometheus Query Language offers you the ability to do all sorts of aggregations, analysis, and arithmetic, allowing you to better understand the performance of your systems from your metrics.
In this part you will be reusing the Prometheus and Node exporter setup you created in Chapter 2, and using the expression browser to execute queries.
Chapter 13 covers the basics of PromQL, and how you can use the HTTP API to evaluate expressions.
Chapter 14 looks in depth into how aggregation works.
Chapter 15 covers operators such as addition and comparisons, and how you can join different metrics together.
Chapter 16 goes into the wide variety of functions that PromQL offers you, from knowing the time of day to predicting when your hard disk will fill up.
PromQL rules. Chapter 17 covers the recording rule feature of Prometheus, which allows you to precompute metrics for faster and more sophisticated querying with PromQL.