refactor metrics, fix deps

src/core/healthCheck.ts

@@ -0,0 +1,95 @@
+export enum HEALTH_STATUS {
+	Ok = 0,
+	StaleBulkAccountLoader,
+	UnhealthySlotSubscriber,
+	LivenessTesting,
+	Restart,
+}
+
+/**
+ * Health check configuration
+ */
+const HEALTH_CHECK_CONFIG = {
+	CHECK_INTERVAL_MS: 2000,
+	// Maximum time allowed between slot updates
+	MAX_SLOT_STALENESS_MS: 5000,
+	// Minimum expected slot advancement rate (slots per second)
+	MIN_SLOT_RATE: 1,
+} as const;
+
+/**
+ * Tracks the health state of the slot subscriber
+ */
+type HealthState = {
+	lastSlot: number;
+	lastSlotTimestamp: number;
+};
+
+const globalHealthState: HealthState = {
+	lastSlot: -1,
+	lastSlotTimestamp: Date.now(),
+};
+
+/**
+ * Evaluates if the current state is healthy based on slot progression
+ */
+function evaluateHealth(currentSlot: number): {
+	isHealthy: boolean;
+	reason?: string;
+} {
+	const now = Date.now();
+
+	// First health check
+	if (globalHealthState.lastSlot === -1) {
+		globalHealthState.lastSlot = currentSlot;
+		globalHealthState.lastSlotTimestamp = now;
+		return { isHealthy: true };
+	}
+
+	const timeDelta = now - globalHealthState.lastSlotTimestamp;
+	const slotDelta = currentSlot - globalHealthState.lastSlot;
+
+	// Update state if slot has progressed
+	if (currentSlot > globalHealthState.lastSlot) {
+		globalHealthState.lastSlot = currentSlot;
+		globalHealthState.lastSlotTimestamp = now;
+	}
+
+	// Check if slots are too stale
+	if (timeDelta > HEALTH_CHECK_CONFIG.MAX_SLOT_STALENESS_MS) {
+		return {
+			isHealthy: false,
+			reason: `No slot updates in ${timeDelta}ms (max ${HEALTH_CHECK_CONFIG.MAX_SLOT_STALENESS_MS}ms)`,
+		};
+	}
+
+	// Check if slot update rate is too low
+	const slotRate = (slotDelta / timeDelta) * 1000; // Convert to per second
+	if (slotRate < HEALTH_CHECK_CONFIG.MIN_SLOT_RATE) {
+		return {
+			isHealthy: false,
+			reason: `Slot update rate ${slotRate.toFixed(
+				2
+			)} slots/sec below minimum ${HEALTH_CHECK_CONFIG.MIN_SLOT_RATE}`,
+		};
+	}
+
+	return { isHealthy: true };
+}
+
+let healthStatus: HEALTH_STATUS = HEALTH_STATUS.Ok;
+const setHealthStatus = (status: HEALTH_STATUS): void => {
+	healthStatus = status;
+};
+
+const getHealthStatus = (): HEALTH_STATUS => {
+	return healthStatus;
+};
+
+export {
+	evaluateHealth,
+	globalHealthState,
+	HEALTH_CHECK_CONFIG,
+	setHealthStatus,
+	getHealthStatus,
+};