From 752c15009b0d97fcaf2dbb40460cd8167ecc391f Mon Sep 17 00:00:00 2001
From: Fuwn <contact@fuwn.me>
Date: Wed, 21 Jan 2026 06:21:55 -0800
Subject: perf: Implement zero-downtime configuration reload

---
 cmd/kaze/main.go | 46 ++++++----------------------------------------
 1 file changed, 6 insertions(+), 40 deletions(-)

(limited to 'cmd')

diff --git a/cmd/kaze/main.go b/cmd/kaze/main.go
index f9e9cd4..e010223 100644
--- a/cmd/kaze/main.go
+++ b/cmd/kaze/main.go
@@ -132,7 +132,7 @@ func main() {
 	logger.Info("kaze is running",
 		"address", fmt.Sprintf("http://%s:%d", cfg.Server.Host, cfg.Server.Port))
 
-	// Reload function (returns error for API endpoint)
+	// Reload function for API endpoint and SIGHUP - performs zero-downtime reload
 	var reloadConfig func() error
 	reloadConfig = func() error {
 		logger.Info("reloading configuration...")
@@ -153,11 +153,8 @@ func main() {
 		sched.Stop()
 		logger.Debug("stopped scheduler")
 
-		// Update config reference
-		cfg = newCfg
-
 		// Create new scheduler with updated config
-		newSched, err := monitor.NewScheduler(cfg, store, logger, *configPath)
+		newSched, err := monitor.NewScheduler(newCfg, store, logger, *configPath)
 		if err != nil {
 			logger.Error("failed to create new scheduler", "error", err)
 			// Restart old scheduler
@@ -165,44 +162,13 @@ func main() {
 			return fmt.Errorf("failed to create new scheduler: %w", err)
 		}
 
-		// Replace scheduler
+		// Swap config/scheduler without restarting the HTTP listener
+		srv.UpdateConfig(newCfg, newSched)
+		cfg = newCfg
 		sched = newSched
 		sched.Start()
 
-		// Stop old server
-		shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 5*time.Second)
-		if err := srv.Stop(shutdownCtx); err != nil {
-			logger.Error("error stopping old server", "error", err)
-		}
-		shutdownCancel()
-
-		// Create new server with updated config
-		newSrv, err := server.New(cfg, store, sched, logger)
-		if err != nil {
-			logger.Error("failed to create new server", "error", err)
-			// Try to restart old server
-			go func() {
-				if err := srv.Start(); err != nil {
-					logger.Error("server error", "error", err)
-				}
-			}()
-			return fmt.Errorf("failed to create new server: %w", err)
-		}
-
-		// Replace server and set reload func and version on new server
-		srv = newSrv
-		srv.SetVersion(version, commit, date)
-		srv.SetReloadFunc(reloadConfig)
-
-		// Start new server
-		go func() {
-			if err := srv.Start(); err != nil {
-				logger.Error("server error", "error", err)
-				cancel()
-			}
-		}()
-
-		logger.Info("configuration reloaded successfully",
+		logger.Info("configuration reloaded successfully (zero-downtime)",
 			"groups", len(cfg.Groups),
 			"incidents", len(cfg.Incidents))
 
-- 
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