Counter, Gauge, Histogram #

The objects returned by the declaration methods of Metrics.

import { Counter, Gauge, Histogram, LabelValues } from 'kuzzle-prometheus';

Their methods depend on the metric's labels:

a metric declared without labelNames takes no labels argument;
otherwise, every method takes the label values first, as a LabelValues<L> object (Record<L, string | number>) that must give every label.

const errors = metrics.counter({
  name: 'decode_errors_total',
  help: 'Payloads that could not be decoded',
  labelNames: ['protocol'],
});

errors.inc({ protocol: 'mqtt' }); // ok
errors.inc({ proto: 'mqtt' }); // type error: unknown label
errors.inc(); // type error: protocol is missing

A label combination past maxLabelSets is dropped (see Keep labels bounded).

Counter #

Without labels	With labels	Description
`inc(value?: number): void`	`inc(labels: LabelValues<L>, value?: number): void`	adds `value` (default `1`)

Gauge #

Without labels	With labels	Description
`set(value: number): void`	`set(labels: LabelValues<L>, value: number): void`	sets the value
`inc(value?: number): void`	`inc(labels: LabelValues<L>, value?: number): void`	adds `value` (default `1`)
`dec(value?: number): void`	`dec(labels: LabelValues<L>, value?: number): void`	subtracts `value` (default `1`)

Histogram #

Without labels	With labels	Description
`observe(value: number): void`	`observe(labels: LabelValues<L>, value: number): void`	records a value
`startTimer(): () => number`	`startTimer(labels: LabelValues<L>): () => number`	starts a timer; the returned function records the elapsed time, in seconds, and returns it

const duration = metrics.histogram({
  name: 'decode_duration_seconds',
  help: 'Time to decode a payload',
  labelNames: ['protocol'],
});

const stop = duration.startTimer({ protocol: 'mqtt' });
decode(payload);
const seconds = stop();