refactor metrics, fix deps

src/core/middleware.ts

@@ -1,15 +1,20 @@
 import { Request, Response } from 'express';
 import responseTime = require('response-time');
-import {
-	endpointResponseTimeHistogram,
-	responseStatusCounter,
-} from './metrics';
 import { MEASURED_ENDPOINTS } from '../utils/constants';
+import { SlotSource } from '@drift-labs/sdk';
+import {
+	evaluateHealth,
+	globalHealthState,
+	setHealthStatus,
+	HEALTH_STATUS,
+} from './healthCheck';
+import { logger } from '../utils/logger';
+import { GaugeValue } from './metricsV2';
 
 export const handleResponseTime = (
 	measuredEndpoints: string[] = MEASURED_ENDPOINTS
 ) => {
-	return responseTime((req: Request, res: Response, time: number) => {
+	return responseTime((req: Request, _res: Response, _time: number) => {
 		const endpoint = req.path;
 
 		if (!measuredEndpoints.includes(endpoint)) {
@@ -19,14 +24,60 @@ export const handleResponseTime = (
 		//  return;
 		//}
 
-		responseStatusCounter.add(1, {
-			endpoint,
-			status: res.statusCode,
-		});
+		// TODO: add these back if want to profile response times
 
-		const responseTimeMs = time;
-		endpointResponseTimeHistogram.record(responseTimeMs, {
-			endpoint,
-		});
+		// responseStatusCounter.add(1, {
+		// 	endpoint,
+		// 	status: res.statusCode,
+		// });
+
+		// const responseTimeMs = time;
+		// endpointResponseTimeHistogram.record(responseTimeMs, {
+		// 	endpoint,
+		// });
 	});
 };
+
+/**
+ * Middleware that checks the health of the slot subscriber.
+ * Health is determined by:
+ * 1. Regular slot updates
+ * 2. Minimum slot update rate
+ */
+export const handleHealthCheck = (
+	slotSource: SlotSource,
+	healthCheckGauge?: GaugeValue
+) => {
+	return async (_req, res, _next) => {
+		const currentSlot = slotSource.getSlot();
+		const { isHealthy, reason } = evaluateHealth(currentSlot);
+
+		if (!isHealthy) {
+			logger.error(
+				`Unhealthy: ${reason}, ` +
+					`Details: currentSlot=${currentSlot}, ` +
+					`lastSlot=${globalHealthState.lastSlot}, ` +
+					`timeSinceLastSlot=${
+						Date.now() - globalHealthState.lastSlotTimestamp
+					}ms`
+			);
+			if (healthCheckGauge) {
+				healthCheckGauge.setLatestValue(
+					Number(HEALTH_STATUS.UnhealthySlotSubscriber),
+					{}
+				);
+			}
+			setHealthStatus(HEALTH_STATUS.UnhealthySlotSubscriber);
+			res.writeHead(500);
+			res.end('NOK');
+			return;
+		}
+
+		if (healthCheckGauge) {
+			healthCheckGauge.setLatestValue(Number(HEALTH_STATUS.Ok), {});
+		}
+		setHealthStatus(HEALTH_STATUS.Ok);
+		res.writeHead(200);
+		res.end('OK');
+	};
+};