Viper map lock (#8)

* Add RWMutex protecting viper maps

* Update README

README.md

@@ -1,4 +1,8 @@
-> ## Viper v2 feedback
+# Fork of spf13/viper that makes it safe for concurrent access
+
+Forked from version 1.9.0 of `spf13/viper`. Adds an `RWMutex` to the `viper` struct that is used to protect reads and writes to the struct's internal maps. This should stop some our servers' intermittent crashing.
+
+> > ## Viper v2 feedback
 > Viper is heading towards v2 and we would love to hear what _**you**_ would like to see in it. Share your thoughts here: https://forms.gle/R6faU74qPRPAzchZ9
 >
 > **Thank you!**

viper.go

@@ -223,6 +223,8 @@ type Viper struct {
 	// TODO: should probably be protected with a mutex
 	encoderRegistry *encoding.EncoderRegistry
 	decoderRegistry *encoding.DecoderRegistry
+
+	mapLock sync.RWMutex
 }
 
 // New returns an initialized Viper instance.
@@ -243,6 +245,8 @@ func New() *Viper {
 	v.typeByDefValue = false
 	v.logger = jwwLogger{}
 
+	v.mapLock = sync.RWMutex{}
+
 	v.resetEncoding()
 
 	return v
@@ -658,7 +662,9 @@ func (v *Viper) searchMap(source map[string]interface{}, path []string) interfac
 		return source
 	}
 
+	v.mapLock.RLock()
 	next, ok := source[path[0]]
+	v.mapLock.RUnlock()
 	if ok {
 		// Fast path
 		if len(path) == 1 {
@@ -763,7 +769,9 @@ func (v *Viper) searchMapWithPathPrefixes(
 	pathIndex int,
 	path []string,
 ) interface{} {
+	v.mapLock.RLock()
 	next, ok := sourceMap[prefixKey]
+	v.mapLock.RUnlock()
 	if !ok {
 		return nil
 	}
@@ -832,7 +840,10 @@ func (v *Viper) isPathShadowedInFlatMap(path []string, mi interface{}) string {
 	var parentKey string
 	for i := 1; i < len(path); i++ {
 		parentKey = strings.Join(path[0:i], v.keyDelim)
-		if _, ok := m[parentKey]; ok {
+		v.mapLock.RLock()
+		_, ok := m[parentKey]
+		v.mapLock.RUnlock()
+		if ok {
 			return parentKey
 		}
 	}
@@ -1456,9 +1467,13 @@ func (v *Viper) RegisterAlias(alias string, key string) {
 func (v *Viper) registerAlias(alias string, key string) {
 	alias = strings.ToLower(alias)
 	if alias != key && alias != v.realKey(key) {
+		v.mapLock.RLock()
 		_, exists := v.aliases[alias]
+		v.mapLock.RUnlock()
 
 		if !exists {
+			v.mapLock.Lock()
+
 			// if we alias something that exists in one of the maps to another
 			// name, we'll never be able to get that value using the original
 			// name, so move the config value to the new realkey.
@@ -1479,6 +1494,8 @@ func (v *Viper) registerAlias(alias string, key string) {
 				v.override[key] = val
 			}
 			v.aliases[alias] = key
+
+			v.mapLock.Unlock()
 		}
 	} else {
 		v.logger.Warn("creating circular reference alias", "alias", alias, "key", key, "real_key", v.realKey(key))
@@ -1523,7 +1540,9 @@ func (v *Viper) SetDefault(key string, value interface{}) {
 	deepestMap := deepSearch(v.defaults, path[0:len(path)-1])
 
 	// set innermost value
+	v.mapLock.Lock()
 	deepestMap[lastKey] = value
+	v.mapLock.Unlock()
 }
 
 // Set sets the value for the key in the override register.
@@ -1542,7 +1561,9 @@ func (v *Viper) Set(key string, value interface{}) {
 	deepestMap := deepSearch(v.override, path[0:len(path)-1])
 
 	// set innermost value
+	v.mapLock.Lock()
 	deepestMap[lastKey] = value
+	v.mapLock.Unlock()
 }
 
 // ReadInConfig will discover and load the configuration file from disk
@@ -1627,8 +1648,10 @@ func (v *Viper) MergeConfigMap(cfg map[string]interface{}) error {
 	if v.config == nil {
 		v.config = make(map[string]interface{})
 	}
+	v.mapLock.Lock()
 	insensitiviseMap(cfg)
 	mergeMaps(cfg, v.config, nil)
+	v.mapLock.Unlock()
 	return nil
 }
 
@@ -1716,6 +1739,9 @@ func unmarshalReader(in io.Reader, c map[string]interface{}) error {
 }
 
 func (v *Viper) unmarshalReader(in io.Reader, c map[string]interface{}) error {
+	v.mapLock.Lock()
+	defer v.mapLock.Unlock()
+
 	buf := new(bytes.Buffer)
 	buf.ReadFrom(in)