Chapter 7, Prometheus Query Language - PromQL

1. The comparison operators are < (less than), > (greater than), == (equals), != (differs), => (greater than or equal to), and <= (less than or equal to).
2. When the time series you want to enrich are on the right-hand side of the PromQL expression.
3. topk already sorts its results.
4. While the rate() function provides the per-second average rate of change over the specified interval by using the first and last values in the range scaled to fit the range window, the irate() function uses the last two values in the range for the calculation, which produces the instant rate of change.
5. Metrics of type info have their names ending in _info and are regular gauges with one possible value, 1. This special kind of metric was designed to be a place where labels whose values might change over time are stored, such as versions (for example...