add VolumeStreamFollow, but not used yet

weed/server/volume_grpc_copy_incremental.go

@@ -18,9 +18,9 @@ func (vs *VolumeServer) VolumeIncrementalCopy(req *volume_server_pb.VolumeIncrem
 	}
 
 	stopOffset := v.Size()
-	foundOffset, isLastOne, err := v.BinarySearchByAppendAtNs(req.Since)
+	foundOffset, isLastOne, err := v.BinarySearchByAppendAtNs(req.SinceNs)
 	if err != nil {
-		return fmt.Errorf("fail to locate by appendAtNs %d: %s", req.Since, err)
+		return fmt.Errorf("fail to locate by appendAtNs %d: %s", req.SinceNs, err)
 	}
 
 	if isLastOne {

weed/server/volume_grpc_stream_follow.go

@@ -0,0 +1,77 @@
+package weed_server
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"github.com/chrislusf/seaweedfs/weed/pb/volume_server_pb"
+	"github.com/chrislusf/seaweedfs/weed/storage"
+)
+
+func (vs *VolumeServer) VolumeStreamFollow(req *volume_server_pb.VolumeStreamFollowRequest, stream volume_server_pb.VolumeServer_VolumeStreamFollowServer) error {
+
+	v := vs.store.GetVolume(storage.VolumeId(req.VolumeId))
+	if v == nil {
+		return fmt.Errorf("not found volume id %d", req.VolumeId)
+	}
+
+	lastTimestampNs := req.SinceNs
+	drainingSeconds := req.DrainingSeconds
+
+	ticker := time.NewTicker(time.Second)
+
+	for {
+		select {
+		case <-ticker.C:
+			lastProcessedTimestampNs, err := sendNeedlesSince(stream, v, lastTimestampNs)
+			if err != nil {
+				return fmt.Errorf("streamFollow: %v", err)
+			}
+			if req.DrainingSeconds == 0 {
+				continue
+			}
+			if lastProcessedTimestampNs == lastTimestampNs {
+				drainingSeconds--
+				if drainingSeconds <= 0 {
+					return nil
+				}
+				glog.V(0).Infof("volume %d drains requests with %d seconds remaining ...", v.Id, drainingSeconds)
+			} else {
+				drainingSeconds = req.DrainingSeconds
+				glog.V(0).Infof("volume %d resets draining wait time to %d seconds", v.Id, drainingSeconds)
+			}
+		}
+	}
+
+}
+
+func sendNeedlesSince(stream volume_server_pb.VolumeServer_VolumeStreamFollowServer, v *storage.Volume, lastTimestampNs uint64) (lastProcessedTimestampNs uint64, err error) {
+
+	foundOffset, isLastOne, err := v.BinarySearchByAppendAtNs(lastTimestampNs)
+	if err != nil {
+		return 0, fmt.Errorf("fail to locate by appendAtNs %d: %s", lastTimestampNs, err)
+	}
+
+	if isLastOne {
+		return lastTimestampNs, nil
+	}
+
+	err = storage.ScanVolumeFileNeedleFrom(v.Version(), v.DataFile(), foundOffset.ToAcutalOffset(), func(needleHeader, needleBody []byte, needleAppendAtNs uint64) error {
+
+		sendErr := stream.Send(&volume_server_pb.VolumeStreamFollowResponse{
+			NeedleHeader: needleHeader,
+			NeedleBody:   needleBody,
+		})
+		if sendErr != nil {
+			return sendErr
+		}
+
+		lastProcessedTimestampNs = needleAppendAtNs
+		return nil
+
+	})
+
+	return
+
+}