Add health check endpoints (/health and /ready) for container orchestration liveness and readiness probes. (#104)

* added health endpoint

* formatted files

---------

Co-authored-by: lxowalle <83055338+lxowalle@users.noreply.github.com>

pkg/health/server.go

@@ -0,0 +1,164 @@
+package health
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"sync"
+	"time"
+)
+
+type Server struct {
+	server    *http.Server
+	mu        sync.RWMutex
+	ready     bool
+	checks    map[string]Check
+	startTime time.Time
+}
+
+type Check struct {
+	Name      string    `json:"name"`
+	Status    string    `json:"status"`
+	Message   string    `json:"message,omitempty"`
+	Timestamp time.Time `json:"timestamp"`
+}
+
+type StatusResponse struct {
+	Status string           `json:"status"`
+	Uptime string           `json:"uptime"`
+	Checks map[string]Check `json:"checks,omitempty"`
+}
+
+func NewServer(host string, port int) *Server {
+	mux := http.NewServeMux()
+	s := &Server{
+		ready:     false,
+		checks:    make(map[string]Check),
+		startTime: time.Now(),
+	}
+
+	mux.HandleFunc("/health", s.healthHandler)
+	mux.HandleFunc("/ready", s.readyHandler)
+
+	addr := fmt.Sprintf("%s:%d", host, port)
+	s.server = &http.Server{
+		Addr:         addr,
+		Handler:      mux,
+		ReadTimeout:  5 * time.Second,
+		WriteTimeout: 5 * time.Second,
+	}
+
+	return s
+}
+
+func (s *Server) Start() error {
+	s.mu.Lock()
+	s.ready = true
+	s.mu.Unlock()
+	return s.server.ListenAndServe()
+}
+
+func (s *Server) StartContext(ctx context.Context) error {
+	s.mu.Lock()
+	s.ready = true
+	s.mu.Unlock()
+
+	errCh := make(chan error, 1)
+	go func() {
+		errCh <- s.server.ListenAndServe()
+	}()
+
+	select {
+	case err := <-errCh:
+		return err
+	case <-ctx.Done():
+		return s.server.Shutdown(context.Background())
+	}
+}
+
+func (s *Server) Stop(ctx context.Context) error {
+	s.mu.Lock()
+	s.ready = false
+	s.mu.Unlock()
+	return s.server.Shutdown(ctx)
+}
+
+func (s *Server) SetReady(ready bool) {
+	s.mu.Lock()
+	s.ready = ready
+	s.mu.Unlock()
+}
+
+func (s *Server) RegisterCheck(name string, checkFn func() (bool, string)) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	status, msg := checkFn()
+	s.checks[name] = Check{
+		Name:      name,
+		Status:    statusString(status),
+		Message:   msg,
+		Timestamp: time.Now(),
+	}
+}
+
+func (s *Server) healthHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+
+	uptime := time.Since(s.startTime)
+	resp := StatusResponse{
+		Status: "ok",
+		Uptime: uptime.String(),
+	}
+
+	json.NewEncoder(w).Encode(resp)
+}
+
+func (s *Server) readyHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+
+	s.mu.RLock()
+	ready := s.ready
+	checks := make(map[string]Check)
+	for k, v := range s.checks {
+		checks[k] = v
+	}
+	s.mu.RUnlock()
+
+	if !ready {
+		w.WriteHeader(http.StatusServiceUnavailable)
+		json.NewEncoder(w).Encode(StatusResponse{
+			Status: "not ready",
+			Checks: checks,
+		})
+		return
+	}
+
+	for _, check := range checks {
+		if check.Status == "fail" {
+			w.WriteHeader(http.StatusServiceUnavailable)
+			json.NewEncoder(w).Encode(StatusResponse{
+				Status: "not ready",
+				Checks: checks,
+			})
+			return
+		}
+	}
+
+	w.WriteHeader(http.StatusOK)
+	uptime := time.Since(s.startTime)
+	json.NewEncoder(w).Encode(StatusResponse{
+		Status: "ready",
+		Uptime: uptime.String(),
+		Checks: checks,
+	})
+}
+
+func statusString(ok bool) string {
+	if ok {
+		return "ok"
+	}
+	return "fail"
+}