rename folder and actually sanity check

src/core/metrics.ts

@@ -0,0 +1,142 @@
+import { ObservableResult } from '@opentelemetry/api';
+import { PrometheusExporter } from '@opentelemetry/exporter-prometheus';
+import { logger } from '../utils/logger';
+import {
+	ExplicitBucketHistogramAggregation,
+	InstrumentType,
+	MeterProvider,
+	View,
+} from '@opentelemetry/sdk-metrics-base';
+import { commitHash, driftEnv, endpoint, wsEndpoint } from '..';
+
+/**
+ * Creates {count} buckets of size {increment} starting from {start}. Each bucket stores the count of values within its "size".
+ * @param start
+ * @param increment
+ * @param count
+ * @returns
+ */
+const createHistogramBuckets = (
+	start: number,
+	increment: number,
+	count: number
+) => {
+	return new ExplicitBucketHistogramAggregation(
+		Array.from(new Array(count), (_, i) => start + i * increment)
+	);
+};
+
+enum METRIC_TYPES {
+	runtime_specs = 'runtime_specs',
+	endpoint_response_times_histogram = 'endpoint_response_times_histogram',
+	endpoint_response_status = 'endpoint_response_status',
+	health_status = 'health_status',
+}
+
+export enum HEALTH_STATUS {
+	Ok = 0,
+	StaleBulkAccountLoader,
+	UnhealthySlotSubscriber,
+	LivenessTesting,
+}
+
+const metricsPort =
+	parseInt(process.env.METRICS_PORT) || PrometheusExporter.DEFAULT_OPTIONS.port;
+const { endpoint: defaultEndpoint } = PrometheusExporter.DEFAULT_OPTIONS;
+const exporter = new PrometheusExporter(
+	{
+		port: metricsPort,
+		endpoint: defaultEndpoint,
+	},
+	() => {
+		logger.info(
+			`prometheus scrape endpoint started: http://localhost:${metricsPort}${defaultEndpoint}`
+		);
+	}
+);
+const meterName = 'dlob-meter';
+const meterProvider = new MeterProvider({
+	views: [
+		new View({
+			instrumentName: METRIC_TYPES.endpoint_response_times_histogram,
+			instrumentType: InstrumentType.HISTOGRAM,
+			meterName,
+			aggregation: createHistogramBuckets(0, 20, 30),
+		}),
+	],
+});
+meterProvider.addMetricReader(exporter);
+const meter = meterProvider.getMeter(meterName);
+
+const runtimeSpecsGauge = meter.createObservableGauge(
+	METRIC_TYPES.runtime_specs,
+	{
+		description: 'Runtime sepcification of this program',
+	}
+);
+const bootTimeMs = Date.now();
+runtimeSpecsGauge.addCallback((obs) => {
+	obs.observe(bootTimeMs, {
+		commit: commitHash,
+		driftEnv,
+		rpcEndpoint: endpoint,
+		wsEndpoint: wsEndpoint,
+	});
+});
+
+let healthStatus: HEALTH_STATUS = HEALTH_STATUS.Ok;
+const healthStatusGauge = meter.createObservableGauge(
+	METRIC_TYPES.health_status,
+	{
+		description: 'Health status of this program',
+	}
+);
+healthStatusGauge.addCallback((obs: ObservableResult) => {
+	obs.observe(healthStatus, {});
+});
+
+const endpointResponseTimeHistogram = meter.createHistogram(
+	METRIC_TYPES.endpoint_response_times_histogram,
+	{
+		description: 'Duration of endpoint responses',
+		unit: 'ms',
+	}
+);
+
+const responseStatusCounter = meter.createCounter(
+	METRIC_TYPES.endpoint_response_status,
+	{
+		description: 'Count of endpoint responses by status code',
+	}
+);
+
+const startupTime = Date.now();
+const handleHealthCheck = async (req, res, next) => {
+	try {
+		if (req.url === '/health' || req.url === '/') {
+			if (Date.now() > startupTime + 60 * 1000) {
+				healthStatus = HEALTH_STATUS.LivenessTesting;
+
+				res.writeHead(500);
+				res.end('Testing liveness test fail');
+				return;
+			}
+
+			// liveness check passed
+			healthStatus = HEALTH_STATUS.Ok;
+			res.writeHead(200);
+			res.end('OK');
+		} else {
+			res.writeHead(404);
+			res.end('Not found');
+		}
+	} catch (e) {
+		next(e);
+	}
+};
+
+export {
+	endpointResponseTimeHistogram,
+	responseStatusCounter,
+	handleHealthCheck,
+};