health-check-endpoints

Health Check Endpoints Skill

Step 1 — Liveness Endpoint

GET /health/live

Purpose: tells Kubernetes whether the process is alive. If this fails, the pod is restarted. Do not check external dependencies here — a database outage should not restart all pods.

// Go example
func livenessHandler(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusOK)
    json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
}

Rules:

• Always returns 200 OK unless the process is deadlocked or terminally broken.
• No database, cache, or broker calls.
• Response time < 5 ms.

Step 2 — Readiness Endpoint

GET /health/ready

Purpose: tells Kubernetes whether the pod can accept traffic. If this fails, the pod is removed from the load balancer (but not restarted). Check all dependencies the service needs to serve requests.

// Go example
func readinessHandler(w http.ResponseWriter, r *http.Request) {
    checks := map[string]CheckResult{}
    overall := "ok"

    // Database check
    ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
    defer cancel()
    if err := db.PingContext(ctx); err != nil {
        checks["db"] = CheckResult{Status: "fail", Error: err.Error()}
        overall = "fail"
    } else {
        start := time.Now()
        db.PingContext(ctx)
        checks["db"] = CheckResult{Status: "ok", LatencyMs: time.Since(start).Milliseconds()}
    }

    // Redis check
    if err := cache.Ping(r.Context()).Err(); err != nil {
        checks["cache"] = CheckResult{Status: "fail", Error: err.Error()}
        overall = "fail"
    } else {
        checks["cache"] = CheckResult{Status: "ok"}
    }

    status := http.StatusOK
    if overall == "fail" {
        status = http.StatusServiceUnavailable
    }

    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(status)
    json.NewEncoder(w).Encode(HealthResponse{Status: overall, Checks: checks})
}