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backend/internal/api/server_keepalive.go

@@ -0,0 +1,89 @@
+package api
+
+import (
+	"crypto/subtle"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	log "github.com/sirupsen/logrus"
+)
+
+func (s *Server) enableKeepAlive(timeout time.Duration, onTimeout func()) {
+	if timeout <= 0 || onTimeout == nil {
+		return
+	}
+
+	s.keepAliveEnabled = true
+	s.keepAliveTimeout = timeout
+	s.keepAliveOnTimeout = onTimeout
+	s.keepAliveHeartbeat = make(chan struct{}, 1)
+	s.keepAliveStop = make(chan struct{}, 1)
+
+	s.engine.GET("/keep-alive", s.handleKeepAlive)
+
+	go s.watchKeepAlive()
+}
+
+func (s *Server) handleKeepAlive(c *gin.Context) {
+	if s.localPassword != "" {
+		provided := strings.TrimSpace(c.GetHeader("Authorization"))
+		if provided != "" {
+			parts := strings.SplitN(provided, " ", 2)
+			if len(parts) == 2 && strings.EqualFold(parts[0], "bearer") {
+				provided = parts[1]
+			}
+		}
+		if provided == "" {
+			provided = strings.TrimSpace(c.GetHeader("X-Local-Password"))
+		}
+		if subtle.ConstantTimeCompare([]byte(provided), []byte(s.localPassword)) != 1 {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid password"})
+			return
+		}
+	}
+
+	s.signalKeepAlive()
+	c.JSON(http.StatusOK, gin.H{"status": "ok"})
+}
+
+func (s *Server) signalKeepAlive() {
+	if !s.keepAliveEnabled {
+		return
+	}
+	select {
+	case s.keepAliveHeartbeat <- struct{}{}:
+	default:
+	}
+}
+
+func (s *Server) watchKeepAlive() {
+	if !s.keepAliveEnabled {
+		return
+	}
+
+	timer := time.NewTimer(s.keepAliveTimeout)
+	defer timer.Stop()
+
+	for {
+		select {
+		case <-timer.C:
+			log.Warnf("keep-alive endpoint idle for %s, shutting down", s.keepAliveTimeout)
+			if s.keepAliveOnTimeout != nil {
+				s.keepAliveOnTimeout()
+			}
+			return
+		case <-s.keepAliveHeartbeat:
+			if !timer.Stop() {
+				select {
+				case <-timer.C:
+				default:
+				}
+			}
+			timer.Reset(s.keepAliveTimeout)
+		case <-s.keepAliveStop:
+			return
+		}
+	}
+}