Merge pull request globalsign#40 from joomcode/feature/fix-concurrency-npd

Fix concurrent `cluster.servers` usage

Author: bozaro

gridfs.go

@@ -678,7 +678,7 @@ func (file *GridFile) insertChunk(data []byte) {
 // an error, if any.
 func (file *GridFile) Seek(offset int64, whence int) (pos int64, err error) {
 	file.m.Lock()
-	debugf("GridFile %p: seeking for %s (whence=%d)", file, offset, whence)
+	debugf("GridFile %p: seeking for %d (whence=%d)", file, offset, whence)
 	defer file.m.Unlock()
 	switch whence {
 	case os.SEEK_SET:

session.go

@@ -872,14 +872,20 @@ func (s *Session) String() string {
 	if cluster == nil {
 		return "<closed session>"
 	}
-	servers := cluster.servers.Slice()
-	allHosts := make([]string, 0, len(servers))
-	for _, server := range servers {
-		allHosts = append(allHosts, server.Addr)
-	}
+	allHosts := func() []string {
+		cluster.Lock()
+		defer cluster.Unlock()
+
+		servers := cluster.servers.Slice()
+		hosts := make([]string, 0, len(servers))
+		for _, server := range servers {
+			hosts = append(hosts, server.Addr)
+		}
+		return hosts
+	}()
 	sort.Strings(allHosts)
 
-	dedupHosts := make([]string, 0, len(servers))
+	dedupHosts := make([]string, 0, len(allHosts))
 	for i, host := range allHosts {
 		if (i == 0) || (allHosts[i-1] != host) {
 			dedupHosts = append(dedupHosts, host)
@@ -3993,7 +3999,7 @@ func (db *Database) run(socket *mongoSocket, cmd, result interface{}) (err error
 	if result != nil {
 		err = bson.Unmarshal(data, result)
 		if err != nil {
-			debugf("Run command unmarshaling failed: %#v", op, err)
+			debugf("Run command unmarshaling failed %#v: %#v", op, err)
 			return err
 		}
 		if globalDebug && globalLogger != nil {