One of my colleagues recently had a question from a customer: is it possible to have one panel in Grafana show a set of all metrics, but the other panels on a dashboard filter to a single metric value from a click in the first panel?
It's an interesting way of working with data, and something that many people find intuitive. If I have a menu of options displayed, I probably want to see only things relevant to one of those options if I click it. Unfortunately, doing that's not something that is immediately obvious in Grafana. For better or worse (and there are good reasons you might not want that behavior!) there's no automatic filtering inside of panels on a dashboard.
Usually people will use dashboard variables for this. Variables provide powerful functionality for filtering queries in Grafana. But they have a drawback: they aren't integrated directly into a dashboard, always appearing at the very top of the screen.
After playing around for a bit, it turns out that there is a way to use variables inside of a panel and have them act the same when you click a value as if you had selected that value from a dropdown at the top of the dashboard. To do this, we can slightly abuse the data links functionality provided by panels.
I'll provide an example of this using Prometheus as a data source, but it should work with any data source you like. We're going off the beaten path in Grafana here. Buckle up, because this one gets a little bumpy!