hdfs: added support for list of namenodes in hdfs remote config

Users can now input a comma separated list of namenodes when writing
config for hdfs remotes.

This is required when you have multiple namenodes in your hdfs cluster
and cannot be certain which namenodes will be in 'standby' or 'active'
states.

This was available before but wasn't documented and didn't use the
correct rclone interfaces.

backend/hdfs/fs.go

@@ -93,7 +93,7 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 	}
 
 	options := hdfs.ClientOptions{
-		Addresses:           []string{opt.Namenode},
+		Addresses:           opt.Namenode,
 		UseDatanodeHostname: false,
 	}
 

backend/hdfs/hdfs.go

@@ -20,9 +20,10 @@ func init() {
 		NewFs:       NewFs,
 		Options: []fs.Option{{
 			Name:      "namenode",
-			Help:      "Hadoop name node and port.\n\nE.g. \"namenode:8020\" to connect to host namenode at port 8020.",
+			Help:      "Hadoop name nodes and ports.\n\nE.g. \"namenode-1:8020,namenode-2:8020,...\" to connect to host namenodes at port 8020.",
 			Required:  true,
 			Sensitive: true,
+			Default:   fs.CommaSepList{},
 		}, {
 			Name: "username",
 			Help: "Hadoop user name.",
@@ -65,7 +66,7 @@ and 'privacy'. Used only with KERBEROS enabled.`,
 
 // Options for this backend
 type Options struct {
-	Namenode               string               `config:"namenode"`
+	Namenode               fs.CommaSepList      `config:"namenode"`
 	Username               string               `config:"username"`
 	ServicePrincipalName   string               `config:"service_principal_name"`
 	DataTransferProtection string               `config:"data_transfer_protection"`