add broker connects to filer

other/java/client/src/main/proto/filer.proto

@@ -48,6 +48,8 @@ service SeaweedFiler {
     rpc SubscribeMetadata (SubscribeMetadataRequest) returns (stream SubscribeMetadataResponse) {
     }
 
+    rpc KeepConnected (stream KeepConnectedRequest) returns (stream KeepConnectedResponse) {
+    }
 }
 
 //////////////////////////////////////////////////
@@ -261,3 +263,10 @@ message LogEntry {
     int32 partition_key_hash = 2;
     bytes data = 3;
 }
+
+message KeepConnectedRequest {
+    string name = 1;
+    uint32 grpc_port = 2;
+}
+message KeepConnectedResponse {
+}