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Golang / GoLang Production Patterns and Web Standards Interview Questions

How do you implement health check and readiness endpoints for a Go service?

Health checks are mandatory for Kubernetes deployments. A liveness probe tells Kubernetes whether the process is running (should it restart?). A readiness probe tells Kubernetes whether the pod should receive traffic (is it ready to serve?).

type HealthChecker struct {
    db    *sql.DB
    cache *redis.Client
    start time.Time
}

func NewHealthChecker(db *sql.DB, cache *redis.Client) *HealthChecker {
    return &HealthChecker{db: db, cache: cache, start: time.Now()}
}

// Liveness: is the process alive? (simple, no dependency checks)
func (h *HealthChecker) LivenessHandler(w http.ResponseWriter, r *http.Request) {
    writeJSON(w, http.StatusOK, map[string]any{
        "status":   "ok",
        "uptime":   time.Since(h.start).String(),
    })
}

// Readiness: can the service handle requests? (checks dependencies)
func (h *HealthChecker) ReadinessHandler(w http.ResponseWriter, r *http.Request) {
    ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
    defer cancel()

    type depStatus struct {
        Status string `json:"status"`
        Error  string `json:"error,omitempty"`
    }

    ready := true
    deps := map[string]depStatus{}

    if err := h.db.PingContext(ctx); err != nil {
        deps["database"] = depStatus{Status: "unhealthy", Error: err.Error()}
        ready = false
    } else {
        deps["database"] = depStatus{Status: "healthy"}
    }

    if err := h.cache.Ping(ctx).Err(); err != nil {
        deps["cache"] = depStatus{Status: "unhealthy", Error: err.Error()}
        ready = false
    } else {
        deps["cache"] = depStatus{Status: "healthy"}
    }

    status := http.StatusOK
    if !ready { status = http.StatusServiceUnavailable }
    writeJSON(w, status, map[string]any{
        "ready":       ready,
        "dependencies": deps,
    })
}

// Register
hc := NewHealthChecker(db, cache)
mux.HandleFunc("GET /healthz", hc.LivenessHandler)    // liveness
mux.HandleFunc("GET /readyz",  hc.ReadinessHandler)   // readiness
What is the difference between a liveness probe and a readiness probe in Kubernetes?
Why should the readiness probe use a short context timeout (e.g., 2 seconds)?

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