Use process.getActiveResourcesInfo() in process metrics

We should use process.getActiveResourcesInfo() here because it is a
public alternative of the private APIs process._getActiveHandles() and
process._getActiveRequests().

Refs: https://nodejs.org/api/process.html#processgetactiveresourcesinfo

Signed-off-by: Darshan Sen <darshan.sen@postman.com>

CHANGELOG.md

@@ -23,6 +23,13 @@ project adheres to [Semantic Versioning](http://semver.org/).
   causing vscode to think that push/pushAdd and delete didn't promise
   resulting in incorrect behavior.
 
+- The `processHandles` and `processRequests` metrics were replaced by the more
+  advanced `processResources` metric, which keeps a track of all sorts of active
+  resources. It consists of the following gauges:
+  - `nodejs_active_resources` - Number of active resources that are currently
+    keeping the event loop alive, grouped by async resource type.
+  - `nodejs_active_resources_total` - Total number of active resources.
+
 ### Added
 
 ## [14.0.0] - 2021-09-18

lib/defaultMetrics.js

@@ -11,6 +11,7 @@ const processMaxFileDescriptors = require('./metrics/processMaxFileDescriptors')
 const eventLoopLag = require('./metrics/eventLoopLag');
 const processHandles = require('./metrics/processHandles');
 const processRequests = require('./metrics/processRequests');
+const processResources = require('./metrics/processResources');
 const heapSizeAndUsed = require('./metrics/heapSizeAndUsed');
 const heapSpacesSizeAndUsed = require('./metrics/heapSpacesSizeAndUsed');
 const version = require('./metrics/version');
@@ -23,8 +24,9 @@ const metrics = {
 	processOpenFileDescriptors,
 	processMaxFileDescriptors,
 	eventLoopLag,
-	processHandles,
-	processRequests,
+	...(typeof process.getActiveResourcesInfo === 'function'
+		? { processResources }
+		: { processHandles, processRequests }),
 	heapSizeAndUsed,
 	heapSpacesSizeAndUsed,
 	version,

lib/metrics/processResources.js

@@ -0,0 +1,58 @@
+'use strict';
+const Gauge = require('../gauge');
+const { updateMetrics } = require('./helpers/processMetricsHelpers');
+
+const NODEJS_ACTIVE_RESOURCES = 'nodejs_active_resources';
+const NODEJS_ACTIVE_RESOURCES_TOTAL = 'nodejs_active_resources_total';
+
+module.exports = (registry, config = {}) => {
+	// Don't do anything if the function does not exist in previous nodes (exists in node@17.3.0)
+	if (typeof process.getActiveResourcesInfo !== 'function') {
+		return;
+	}
+
+	const namePrefix = config.prefix ? config.prefix : '';
+	const labels = config.labels ? config.labels : {};
+	const labelNames = Object.keys(labels);
+
+	new Gauge({
+		name: namePrefix + NODEJS_ACTIVE_RESOURCES,
+		help:
+			'Number of active resources that are currently keeping the event loop alive, grouped by async resource type.',
+		labelNames: ['type', ...labelNames],
+		registers: registry ? [registry] : undefined,
+		collect() {
+			const resources = process.getActiveResourcesInfo();
+
+			const data = {};
+
+			for (let i = 0; i < resources.length; i++) {
+				const resource = resources[i];
+
+				if (Object.hasOwn(data, resource)) {
+					data[resource] += 1;
+				} else {
+					data[resource] = 1;
+				}
+			}
+
+			updateMetrics(this, data, labels);
+		},
+	});
+
+	new Gauge({
+		name: namePrefix + NODEJS_ACTIVE_RESOURCES_TOTAL,
+		help: 'Total number of active resources.',
+		registers: registry ? [registry] : undefined,
+		labelNames,
+		collect() {
+			const resources = process.getActiveResourcesInfo();
+			this.set(labels, resources.length);
+		},
+	});
+};
+
+module.exports.metricNames = [
+	NODEJS_ACTIVE_RESOURCES,
+	NODEJS_ACTIVE_RESOURCES_TOTAL,
+];

test/metrics/processResourcesTest.js

@@ -0,0 +1,37 @@
+'use strict';
+
+describe('processRequests', () => {
+	const register = require('../../index').register;
+	const processResources = require('../../lib/metrics/processResources');
+
+	beforeAll(() => {
+		register.clear();
+	});
+
+	afterEach(() => {
+		register.clear();
+	});
+
+	it('should add metric to the registry', async () => {
+		if (typeof process.getActiveResourcesInfo !== 'function') {
+			return;
+		}
+
+		expect(await register.getMetricsAsJSON()).toHaveLength(0);
+
+		processResources();
+
+		const metrics = await register.getMetricsAsJSON();
+
+		expect(metrics).toHaveLength(2);
+		expect(metrics[0].help).toEqual(
+			'Number of active resources that are currently keeping the event loop alive, grouped by async resource type.',
+		);
+		expect(metrics[0].type).toEqual('gauge');
+		expect(metrics[0].name).toEqual('nodejs_active_resources');
+
+		expect(metrics[1].help).toEqual('Total number of active resources.');
+		expect(metrics[1].type).toEqual('gauge');
+		expect(metrics[1].name).toEqual('nodejs_active_resources_total');
+	});
+});