Prometheus
It's more commonly paired with Prometheus.
Query variables
label_names()
returns a list of label names.label_values(label)
returns a list of values for the given label name.label_values(metric, label)
returns a list of values for the given label name in the given metric.metrics(regex)
yields a list of metrics that match the supplied regular expression.query_result(query)
yields a list of values for the specified query.