schemas/health/health.go

package health

import (
	"context"
	"database/sql"
	"encoding/json"
	"log/slog"
	"net/http"
	"time"
)

type Checker struct {
	db     *sql.DB
	logger *slog.Logger
}

func New(db *sql.DB, logger *slog.Logger) *Checker {
	return &Checker{
		db:     db,
		logger: logger,
	}
}

type HealthStatus struct {
	Status string            `json:"status"`
	Checks map[string]string `json:"checks,omitempty"`
}

// LivenessHandler checks if the application is running
// This is a simple check that always returns OK if the handler is reached
func (h *Checker) LivenessHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	_ = json.NewEncoder(w).Encode(HealthStatus{
		Status: "UP",
	})
}

// ReadinessHandler checks if the application is ready to accept traffic
// This checks database connectivity and other critical dependencies
func (h *Checker) ReadinessHandler(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
	defer cancel()

	checks := make(map[string]string)
	allHealthy := true

	// Check database connectivity
	if err := h.db.PingContext(ctx); err != nil {
		h.logger.With("error", err).Warn("database health check failed")
		checks["database"] = "DOWN"
		allHealthy = false
	} else {
		checks["database"] = "UP"
	}

	status := HealthStatus{
		Status: "UP",
		Checks: checks,
	}

	if !allHealthy {
		status.Status = "DOWN"
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusServiceUnavailable)
		_ = json.NewEncoder(w).Encode(status)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	_ = json.NewEncoder(w).Encode(status)
}