Querying the Prometheus data source

Now that we have a whole ton of Prometheus and Grafana logging metrics, let’s play around with some more queries. I won’t be able to give you a full rundown of every aspect of PromQL—the Prometheus query language—but I can give you enough of a taste to be able to examine many of the server metrics that can be accessed via the Prometheus data source.

To get a better understanding of how queries work in time-series databases such as Prometheus, let’s first start with a more traditional database, such as MySQL. Typically, the structure of a query looks something like this:

SELECT some fields
    FROM some table
    WHERE fields match some criteria

You get back from the query some rows, each one containing the contents of some fields. In the case of time-series databases, things work a little differently. The query has a form that is more like the following:

SELECT...