Understanding the data source limitations
After seeing how powerful even relatively simple PromQL queries can be, it is tempting to think you can query and graph virtually any metric in your data source. Unfortunately, there are limitations to certain kinds of calculations, either imposed by the nature of the data or by the data source application.
It is important to remember that when you create a graph, you are entering into a trust relationship between you and your audience (which might even be you). When you place a pixel on a graph that isn’t explicitly represented by a corresponding data point, you are asking your audience to accept that what you are doing is, in essence, reconstructing a signal from the underlying data.
Therefore, you have an obligation to respect the integrity of the data and not abuse that trust by manipulating the data to say things that aren’t true or lead the viewer to draw erroneous conclusions.
Throughout this book, we’ll...
