@metrics/client/lib/gauge.js

A streaming metric producer. Allows producing counters, gauges, histograms and summaries in a way that is independent of your metrics system.

"use strict";

const assert = require("assert");
const { EventEmitter } = require("events");
const Metric = require("@metrics/metric");

const Gauge = class Gauge extends EventEmitter {
	constructor(options) {
		super();

		assert(typeof options === "object", `argument 'options' must be provided`);

		Object.defineProperty(this, "options", {
			value: {
				labels: {},
				...options,
			},
		});
	}

	set(value, options = {}) {
		assert(typeof value === "number", `argument 'value' to method .set() must be of type 'number'`);

		const labelsObject = {
			...(this.options.labels || {}),
			...(options.labels || {}),
		};

		const labels = Object.keys(labelsObject).map((label) => ({
			name: label,
			value: labelsObject[label],
		}));

		const metric = new Metric({
			name: this.options.name,
			description: this.options.description,
			type: 1,
			value,
			labels,
		});
		this.emit("metric", metric);
	}
};

module.exports = Gauge;