If you work with monitoring or monitoring tools much, you’ve probably seen the phrase “correlating” here and there. For example, monitoring vendors often say you can use their product to correlate metrics. Issue 157 in the popular Prometheus monitoring system’s GitHub repository is to add support to correlate multiple metrics in the same graph.
I’ve noticed that when monitoring-related discussions mention correlation, the meaning is usually pretty vague. It often seems to refer to just graphing multiple things on a single chart with the same timescale. Here’s an example of metrics that seem to be correlated:
But visually aligning metrics isn’t the same thing as correlation. Correlation has a specific meaning, and I think we do ourselves injustice when we get in the habit of blurring that meaning; we lose the real benefits of correlation, we tend to think as imprecisely as we speak, and we teach ourselves and …[Read more]