LDAP: Added reload endpoint for LDAP config (#15470)

* 4843 - Added reload endpoint for LDAP config

closes #4843

* Refactor to make the reload work after master drifted

pkg/services/ldap/settings.go

@@ -2,9 +2,11 @@ package ldap
 
 import (
 	"fmt"
-	"os"
+	"sync"
 
 	"github.com/BurntSushi/toml"
+	"github.com/grafana/grafana/pkg/util/errutil"
+	"golang.org/x/xerrors"
 
 	"github.com/grafana/grafana/pkg/log"
 	m "github.com/grafana/grafana/pkg/models"
@@ -56,47 +58,72 @@ type GroupToOrgRole struct {
 var config *Config
 var logger = log.New("ldap")
 
+// loadingMutex locks the reading of the config so multiple requests for reloading are sequential.
+var loadingMutex = &sync.Mutex{}
+
 // IsEnabled checks if ldap is enabled
 func IsEnabled() bool {
 	return setting.LdapEnabled
 }
 
-// ReadConfig reads the config if
-// ldap is enabled otherwise it will return nil
-func ReadConfig() *Config {
+// ReloadConfig reads the config from the disc and caches it.
+func ReloadConfig() error {
 	if IsEnabled() == false {
 		return nil
 	}
+	loadingMutex.Lock()
+	defer loadingMutex.Unlock()
+
+	var err error
+	config, err = readConfig(setting.LdapConfigFile)
+	return err
+}
+
+// GetConfig returns the LDAP config if LDAP is enabled otherwise it returns nil. It returns either cached value of
+// the config or it reads it and caches it first.
+func GetConfig() (*Config, error) {
+	if IsEnabled() == false {
+		return nil, nil
+	}
 
 	// Make it a singleton
 	if config != nil {
-		return config
+		return config, nil
 	}
 
-	config = getConfig(setting.LdapConfigFile)
+	loadingMutex.Lock()
+	defer loadingMutex.Unlock()
 
-	return config
+	var err error
+	config, err = readConfig(setting.LdapConfigFile)
+
+	return config, err
 }
-func getConfig(configFile string) *Config {
+
+func readConfig(configFile string) (*Config, error) {
 	result := &Config{}
 
 	logger.Info("Ldap enabled, reading config file", "file", configFile)
 
 	_, err := toml.DecodeFile(configFile, result)
 	if err != nil {
-		logger.Crit("Failed to load ldap config file", "error", err)
-		os.Exit(1)
+		return nil, errutil.Wrap("Failed to load ldap config file", err)
 	}
 
 	if len(result.Servers) == 0 {
-		logger.Crit("ldap enabled but no ldap servers defined in config file")
-		os.Exit(1)
+		return nil, xerrors.New("ldap enabled but no ldap servers defined in config file")
 	}
 
 	// set default org id
 	for _, server := range result.Servers {
-		assertNotEmptyCfg(server.SearchFilter, "search_filter")
-		assertNotEmptyCfg(server.SearchBaseDNs, "search_base_dns")
+		err = assertNotEmptyCfg(server.SearchFilter, "search_filter")
+		if err != nil {
+			return nil, errutil.Wrap("Failed to validate SearchFilter section", err)
+		}
+		err = assertNotEmptyCfg(server.SearchBaseDNs, "search_base_dns")
+		if err != nil {
+			return nil, errutil.Wrap("Failed to validate SearchBaseDNs section", err)
+		}
 
 		for _, groupMap := range server.Groups {
 			if groupMap.OrgId == 0 {
@@ -105,22 +132,21 @@ func getConfig(configFile string) *Config {
 		}
 	}
 
-	return result
+	return result, nil
 }
 
-func assertNotEmptyCfg(val interface{}, propName string) {
+func assertNotEmptyCfg(val interface{}, propName string) error {
 	switch v := val.(type) {
 	case string:
 		if v == "" {
-			logger.Crit("LDAP config file is missing option", "option", propName)
-			os.Exit(1)
+			return xerrors.Errorf("LDAP config file is missing option: %v", propName)
 		}
 	case []string:
 		if len(v) == 0 {
-			logger.Crit("LDAP config file is missing option", "option", propName)
-			os.Exit(1)
+			return xerrors.Errorf("LDAP config file is missing option: %v", propName)
 		}
 	default:
 		fmt.Println("unknown")
 	}
+	return nil
 }