Health Check Endpoints

Table of Contents

• [Overview](#overview)
• [When to Use](#when-to-use)
• [Quick Start](#quick-start)
• [Reference Guides](#reference-guides)
• [Best Practices](#best-practices)

Overview

Implement health check endpoints to monitor service health, dependencies, and readiness for traffic.

When to Use

• Kubernetes liveness and readiness probes
• Load balancer health checks
• Service discovery and registration
• Monitoring and alerting systems
• Circuit breaker decisions
• Auto-scaling triggers
• Deployment verification

Quick Start

Minimal working example:

import express from "express";
import { Pool } from "pg";
import Redis from "ioredis";

interface HealthStatus {
  status: "healthy" | "degraded" | "unhealthy";
  timestamp: string;
  uptime: number;
  checks: Record<string, CheckResult>;
  version?: string;
  environment?: string;
}

interface CheckResult {
  status: "pass" | "fail" | "warn";
  time: number;
  output?: string;
  error?: string;
}

class HealthCheckService {
  private startTime = Date.now();
  private version = process.env.APP_VERSION || "1.0.0";
  private environment = process.env.NODE_ENV || "development";

// ... (see reference guides for full implementation)

Reference Guides

Detailed implementations in the references/ directory:

Best Practices

✅ DO

• Implement separate liveness and readiness probes
• Keep liveness probes lightweight
• Check critical dependencies in readiness
• Return appropriate HTTP status codes
• Include response time metrics
• Set reasonable timeouts
• Cache health check results briefly
• Include version and environment info
• Monitor health check failures

❌ DON'T

• Make liveness probes check dependencies
• Return 200 for failed health checks
• Take too long to respond
• Skip important dependency checks
• Expose sensitive information
• Ignore health check failures