feat: send host metrics

This adds in host metrics, which means we can see things like CPU and
memory usage for apps using Reliability Kit.

Author: rowanmanning

packages/opentelemetry/lib/index.js

@@ -2,6 +2,7 @@ const { createInstrumentationConfig } = require('./config/instrumentations');
 const { createMetricsConfig } = require('./config/metrics');
 const { createResourceConfig } = require('./config/resource');
 const { createTracingConfig } = require('./config/tracing');
+const { HostMetrics } = require('@opentelemetry/host-metrics');
 const opentelemetry = require('@opentelemetry/sdk-node');
 const logger = require('@dotcom-reliability-kit/logger');
 
@@ -27,6 +28,8 @@ const logger = require('@dotcom-reliability-kit/logger');
  * @typedef {object} Instances
  * @property {opentelemetry.NodeSDK} sdk
  *      A singleton instance of the OpenTelemetry Node SDK.
+ * @property {HostMetrics} [hostMetrics]
+ *      A singleton instances of the OpenTelemetry host metrics collector.
  */
 
 /**
@@ -81,6 +84,7 @@ function setupOpenTelemetry({
 
 	// Set up and start OpenTelemetry
 	instances = {
+		hostMetrics: undefined,
 		sdk: new opentelemetry.NodeSDK({
 			// Configurations we set regardless of whether we're using tracing
 			instrumentations: createInstrumentationConfig(),
@@ -98,6 +102,18 @@ function setupOpenTelemetry({
 	};
 	instances.sdk.start();
 
+	// Set up host metrics if we have a metrics endpoint
+	if (metricsOptions?.endpoint) {
+		instances.hostMetrics = new HostMetrics({
+			// This is a little redundant as the HostMetrics package defaults
+			// this value to the package name, _however_ the types disagree and
+			// think that `name` is a required property. Could be fixable in
+			// future, see https://github.com/open-telemetry/opentelemetry-js-contrib/issues/2274
+			name: '@opentelemetry/host-metrics'
+		});
+		instances.hostMetrics.start();
+	}
+
 	return instances;
 }
 

packages/opentelemetry/test/unit/lib/index.spec.js

@@ -1,3 +1,4 @@
+jest.mock('@opentelemetry/host-metrics');
 jest.mock('@opentelemetry/sdk-node');
 jest.mock('@dotcom-reliability-kit/logger');
 jest.mock('../../../lib/config/instrumentations', () => ({
@@ -16,11 +17,12 @@ jest.mock('../../../lib/config/tracing', () => ({
 }));
 
 describe('@dotcom-reliability-kit/opentelemetry', () => {
+	let api;
 	let createInstrumentationConfig;
 	let createMetricsConfig;
 	let createResourceConfig;
 	let createTracingConfig;
-	let api;
+	let HostMetrics;
 	let logger;
 	let NodeSDK;
 	let opentelemetry;
@@ -40,6 +42,7 @@ describe('@dotcom-reliability-kit/opentelemetry', () => {
 		createTracingConfig =
 			require('../../../lib/config/tracing').createTracingConfig;
 		api = require('@opentelemetry/sdk-node').api;
+		HostMetrics = require('@opentelemetry/host-metrics').HostMetrics;
 		NodeSDK = require('@opentelemetry/sdk-node').NodeSDK;
 		logger = require('@dotcom-reliability-kit/logger');
 
@@ -114,9 +117,39 @@ describe('@dotcom-reliability-kit/opentelemetry', () => {
 			expect(NodeSDK.prototype.start).toHaveBeenCalledTimes(1);
 		});
 
-		it('returns the SDK instance', () => {
+		it('instantiates and starts a HostMetrics collector', () => {
+			expect(HostMetrics).toHaveBeenCalledTimes(1);
+			expect(HostMetrics).toHaveBeenCalledWith({
+				name: '@opentelemetry/host-metrics'
+			});
+			expect(HostMetrics.prototype.start).toHaveBeenCalledTimes(1);
+		});
+
+		it('returns the SDK instances', () => {
 			expect(instances).toEqual({
-				sdk: NodeSDK.mock.instances[0]
+				sdk: NodeSDK.mock.instances[0],
+				hostMetrics: HostMetrics.mock.instances[0]
+			});
+		});
+
+		describe('when no metrics endpoint is set', () => {
+			beforeEach(() => {
+				NodeSDK.mockClear();
+				reloadAllModules();
+				instances = opentelemetry.setup({
+					tracing: {
+						endpoint: 'mock-tracing-endpoint',
+						samplePercentage: 137
+					}
+				});
+			});
+
+			it('does not instantiate a HostMetrics collector', () => {
+				expect(HostMetrics).toHaveBeenCalledTimes(0);
+			});
+
+			it('returns instances with hostMetrics undefined', () => {
+				expect(instances.hostMetrics).toBeUndefined();
 			});
 		});