reduce busy waiting when reading metadata logs

weed/messaging/broker/broker_grpc_server_subscribe.go

@@ -128,7 +128,6 @@ func (broker *MessageBroker) Subscribe(stream messaging_pb.SeaweedMessaging_Subs
 				continue
 			}
 			glog.Errorf("processed to %v: %v", lastReadTime, err)
-			time.Sleep(3127 * time.Millisecond)
 			if err != log_buffer.ResumeError {
 				break
 			}

weed/server/filer_grpc_server_sub_meta.go

@@ -63,7 +63,6 @@ func (fs *FilerServer) SubscribeMetadata(req *filer_pb.SubscribeMetadataRequest,
 		}, eachLogEntryFn)
 		if readInMemoryLogErr != nil {
 			if readInMemoryLogErr == log_buffer.ResumeFromDiskError {
-				time.Sleep(1127 * time.Millisecond)
 				continue
 			}
 			glog.Errorf("processed to %v: %v", lastReadTime, readInMemoryLogErr)
@@ -127,7 +126,6 @@ func (fs *FilerServer) SubscribeLocalMetadata(req *filer_pb.SubscribeMetadataReq
 			return true
 		}, eachLogEntryFn)
 		if readInMemoryLogErr != nil {
-			time.Sleep(1127 * time.Millisecond)
 			if readInMemoryLogErr == log_buffer.ResumeFromDiskError {
 				continue
 			}

weed/util/log_buffer/log_read.go

@@ -34,6 +34,7 @@ func (logBuffer *LogBuffer) LoopProcessLogData(readerName string, startTreadTime
 		}
 		bytesBuf, err = logBuffer.ReadFromBuffer(lastReadTime)
 		if err == ResumeFromDiskError {
+			time.Sleep(1127 * time.Millisecond)
 			return lastReadTime, ResumeFromDiskError
 		}
 		// glog.V(4).Infof("%s ReadFromBuffer by %v", readerName, lastReadTime)