From 8958845f65785f1ff50ff95dd6517e5d98495f2d Mon Sep 17 00:00:00 2001
From: yo <johan@nosd.in>
Date: Mon, 13 Jan 2025 20:15:32 +0100
Subject: [PATCH] v0.2.5: Reloading a badly formated configuration wont crash,
 so the old configuration will keep running.

---
 main.go | 58 ++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 41 insertions(+), 17 deletions(-)

diff --git a/main.go b/main.go
index 0dc033d..db55286 100644
--- a/main.go
+++ b/main.go
@@ -34,7 +34,7 @@ import (
 )
 
 const (
-	gVersion = "0.2.4"
+	gVersion = "0.2.5"
 	// Default datasource timeout is 10 seconds
 	gDefaultDSTimeout = 10
 )
@@ -329,7 +329,7 @@ func getGraph(name string) (Graph, error) {
 	return Graph{}, fmt.Errorf("Graph not found: %s", name)
 }
 
-func initRoutes(r *gin.Engine) {
+func initRoutes(r *gin.Engine, confFile string) {
 	r.GET("/ping", func(c *gin.Context) {
 		c.JSON(http.StatusOK, gin.H{
 			"message": "pong",
@@ -338,7 +338,10 @@ func initRoutes(r *gin.Engine) {
 	
 	// An endpoint to force read of configuration file
 	r.POST("/reload", func(c *gin.Context) {
-		reloadConfigFile()
+		if err := reloadConfigFile(confFile); err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+			return
+		}
 		c.JSON(http.StatusOK, gin.H{
 			"message": "configuration successfully reloaded",
 		})
@@ -469,16 +472,32 @@ func newEdgeClone(src *Edge) *Edge {
 	}
 }
 
-func reloadConfigFile() {
-	// First reread config file
-	if err := viper.ReadInConfig(); err != nil {
-		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
-			log.Fatalf("config file not found")
-			os.Exit(1)
+// This function assume we already have a running configuration.
+func reloadConfigFile(confFile string) error {
+	oldConfigRestored := false
+	// We need to keep this config, incase the new one is b0rken
+	fname := fmt.Sprintf("/tmp/nodegopher.%d.yaml", os.Getpid())
+	if err := viper.WriteConfigAs(fname); err != nil {
+		log.Errorf("Unable to save current running config to %s, wont reload configuration.\n", fname)
+		return fmt.Errorf("Unable to save current configuration, configuration not reloaded. See logs.")
+	}
+	defer os.Remove(fname)
+
+	// Reread config file
+	if oldErr := viper.ReadInConfig(); oldErr != nil {
+		if _, ok := oldErr.(viper.ConfigFileNotFoundError); ok {
+			log.Errorf("config file not found")
 		} else {
-			log.Fatalf("unknown error looking for config file: %v", err)
-			os.Exit(1)
+			log.Errorf("unknown error looking for config file: %v", oldErr)
 		}
+		// Restore old configuration and notify.
+		log.Debugf("Fallback on previous configuration.\n")
+		viper.SetConfigFile(fname)
+		if err := viper.ReadInConfig(); err != nil {
+			log.Fatalf("Unable to restore configuration, and new is invalid. fix it now.\n")
+		}
+		viper.SetConfigFile(confFile)
+		oldConfigRestored = true
 	}
 
 	switch viper.Get("language").(string) {
@@ -503,6 +522,7 @@ func reloadConfigFile() {
 	gCfgMutex.Lock()
 	defer gCfgMutex.Unlock()
 
+	// We need to keep this config, incase the new one is b0rken
 	for _, g := range gGraphs {
 		g.Nodes = nil
 		g.Edges = nil
@@ -538,8 +558,8 @@ func reloadConfigFile() {
 	}
 
 	if viper.Get("datasources") == nil {
-		log.Printf("no datasources found, data will be static")
-		return
+		log.Warningf("no datasources found, data will be static")
+		return nil
 	}
 	dss := viper.Get("datasources").([]interface{})
 	for _, d := range dss {
@@ -552,6 +572,10 @@ func reloadConfigFile() {
 		}
 		gDataSources = append(gDataSources, ds)
 	}
+	if oldConfigRestored {
+		return fmt.Errorf("Unable to load new configuration, keeping old one. See logs.")
+	}
+	return nil
 }
 
 func main() {
@@ -604,7 +628,7 @@ func main() {
 	// FIXME: Watch config changes. Does not work on FreeBSD. TODO: Test with linux
 	viper.OnConfigChange(func(e fsnotify.Event) {
 		log.Printf("Config file changed, reloading data\n")
-		reloadConfigFile()
+		reloadConfigFile(confFile)
 	})
 
 	// Lets reload config on SIGHUP
@@ -614,11 +638,11 @@ func main() {
 		for {
 			_ = <- sigs
 			log.Infof("SIGHUP received, reloading configuration\n")
-			reloadConfigFile()
+			reloadConfigFile(confFile)
 		}
 	}()
 
-	reloadConfigFile()
+	reloadConfigFile(confFile)
 
 	// Capture variable name. There should be only one variable. Space is tolerated before and after name.
 	gDSVarCompRegex = regexp.MustCompile(`^\{\{(?:\ )?([a-zA-Z0-9\-_]+)(?:\ )?\}\}$`)
@@ -629,6 +653,6 @@ func main() {
 	log.Printf("Starting NodeGopher v.%s\n", gVersion)
 
 	r := gin.Default()
-	initRoutes(r)
+	initRoutes(r, confFile)
 	r.Run(listen)
 }