Fix some possible race conditions

When launching multiple reva instance for a single process we need to
make sure that the sharedconfig global variable is initialized exactly
once. Otherwise we might run into race conditions. Similarly make sure
to initialize the user cache for the auth interceptor exactly once.

changelog/unreleased/fix-racecond.md

@@ -0,0 +1,6 @@
+Bugfix: Fix possible race conditions
+
+We fixed two potential race condition when initializing the shared config
+structure and when setting up caches for the http authentication interceptors.
+
+https://github.com/cs3org/reva/pull/3xxx

internal/http/interceptors/auth/auth.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"net/http"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/bluele/gcache"
@@ -55,7 +56,10 @@ import (
 // name is the Tracer name used to identify this instrumentation library.
 const tracerName = "auth"
 
-var userGroupsCache gcache.Cache
+var (
+	cacheOnce       sync.Once
+	userGroupsCache gcache.Cache
+)
 
 type config struct {
 	Priority   int    `mapstructure:"priority"`
@@ -116,7 +120,10 @@ func New(m map[string]interface{}, unprotected []string, tp trace.TracerProvider
 	if conf.UserGroupsCacheSize == 0 {
 		conf.UserGroupsCacheSize = 5000
 	}
-	userGroupsCache = gcache.New(conf.UserGroupsCacheSize).LFU().Build()
+
+	cacheOnce.Do(func() {
+		userGroupsCache = gcache.New(conf.UserGroupsCacheSize).LFU().Build()
+	})
 
 	credChain := map[string]auth.CredentialStrategy{}
 	for i, key := range conf.CredentialChain {

pkg/sharedconf/sharedconf.go

@@ -21,11 +21,15 @@ package sharedconf
 import (
 	"fmt"
 	"os"
+	"sync"
 
 	"github.com/mitchellh/mapstructure"
 )
 
-var sharedConf = &conf{}
+var (
+	sharedConf     = &conf{}
+	sharedConfOnce sync.Once
+)
 
 // ClientOptions represent additional options (e.g. tls settings) for the grpc clients
 type ClientOptions struct {
@@ -43,32 +47,35 @@ type conf struct {
 
 // Decode decodes the configuration.
 func Decode(v interface{}) error {
-	if err := mapstructure.Decode(v, sharedConf); err != nil {
-		return err
-	}
+	var err error
 
-	// add some defaults
-	if sharedConf.GatewaySVC == "" {
-		sharedConf.GatewaySVC = "0.0.0.0:19000"
-	}
+	sharedConfOnce.Do(func() {
+		if err = mapstructure.Decode(v, sharedConf); err != nil {
+			return
+		}
+		// add some defaults
+		if sharedConf.GatewaySVC == "" {
+			sharedConf.GatewaySVC = "0.0.0.0:19000"
+		}
 
-	// this is the default address we use for the data gateway HTTP service
-	if sharedConf.DataGateway == "" {
-		host, err := os.Hostname()
-		if err != nil || host == "" {
-			sharedConf.DataGateway = "http://0.0.0.0:19001/datagateway"
-		} else {
-			sharedConf.DataGateway = fmt.Sprintf("http://%s:19001/datagateway", host)
+		// this is the default address we use for the data gateway HTTP service
+		if sharedConf.DataGateway == "" {
+			host, err := os.Hostname()
+			if err != nil || host == "" {
+				sharedConf.DataGateway = "http://0.0.0.0:19001/datagateway"
+			} else {
+				sharedConf.DataGateway = fmt.Sprintf("http://%s:19001/datagateway", host)
+			}
 		}
-	}
 
-	// TODO(labkode): would be cool to autogenerate one secret and print
-	// it on init time.
-	if sharedConf.JWTSecret == "" {
-		sharedConf.JWTSecret = "changemeplease"
-	}
+		// TODO(labkode): would be cool to autogenerate one secret and print
+		// it on init time.
+		if sharedConf.JWTSecret == "" {
+			sharedConf.JWTSecret = "changemeplease"
+		}
+	})
 
-	return nil
+	return err
 }
 
 // GetJWTSecret returns the package level configured jwt secret if not overwritten.