From 71fb06fbb85fcd1cfc3be08cee00a5f58cedfdd0 Mon Sep 17 00:00:00 2001
From: Victor Shyba <victor.shyba@gmail.com>
Date: Mon, 2 Aug 2021 03:23:54 -0300
Subject: [PATCH] sendfile proof of concept

---
 server/peer/server.go | 41 ++++++++++++++++++++---------------------
 store/disk.go         | 21 +++++++++++++++++++++
 2 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/server/peer/server.go b/server/peer/server.go
index 4061ea5..5c8b7a1 100644
--- a/server/peer/server.go
+++ b/server/peer/server.go
@@ -32,15 +32,17 @@ const (
 // Server is an instance of a peer server that houses the listener and store.
 type Server struct {
 	store  store.BlobStore
+	disk   *store.DiskStore
 	closed bool
 
 	grp *stop.Group
 }
 
 // NewServer returns an initialized Server pointer.
-func NewServer(store store.BlobStore) *Server {
+func NewServer(blobstore store.BlobStore) *Server {
 	return &Server{
-		store: store,
+		store: blobstore,
+		disk:  store.NewDiskStore("/external/blobs", 2),
 		grp:   stop.New(),
 	}
 }
@@ -131,7 +133,7 @@ func (s *Server) handleConnection(conn net.Conn) {
 			log.Error(errors.FullTrace(err))
 		}
 
-		response, err = s.handleCompositeRequest(request)
+		response, blobHash, err := s.handleCompositeRequest(request)
 		if err != nil {
 			log.Error(errors.FullTrace(err))
 			return
@@ -143,6 +145,7 @@ func (s *Server) handleConnection(conn net.Conn) {
 		}
 
 		n, err := conn.Write(response)
+		s.disk.Sendfile(blobHash, conn)
 		if err != nil {
 			if !strings.Contains(err.Error(), "connection reset by peer") { // means the other side closed the connection using TCP reset
 				s.logError(err)
@@ -221,15 +224,15 @@ func (s *Server) handleAvailabilityRequest(data []byte) ([]byte, error) {
 //	return append(response, blob...), nil
 //}
 
-func (s *Server) handleCompositeRequest(data []byte) ([]byte, error) {
+func (s *Server) handleCompositeRequest(data []byte) ([]byte, string, error) {
 	var request compositeRequest
 	err := json.Unmarshal(data, &request)
 	if err != nil {
 		var je *json.SyntaxError
 		if ee.As(err, &je) {
-			return nil, errors.Err("invalid json at offset %d in data %s", je.Offset, hex.EncodeToString(data))
+			return nil, "", errors.Err("invalid json at offset %d in data %s", je.Offset, hex.EncodeToString(data))
 		}
-		return nil, errors.Err(err)
+		return nil, "", errors.Err(err)
 	}
 
 	response := compositeResponse{
@@ -241,7 +244,7 @@ func (s *Server) handleCompositeRequest(data []byte) ([]byte, error) {
 		for _, blobHash := range request.RequestedBlobs {
 			exists, err := s.store.Has(blobHash)
 			if err != nil {
-				return nil, err
+				return nil, "", err
 			}
 			if exists {
 				availableBlobs = append(availableBlobs, blobHash)
@@ -256,39 +259,35 @@ func (s *Server) handleCompositeRequest(data []byte) ([]byte, error) {
 	}
 
 	var blob []byte
-	var trace shared.BlobTrace
 	if request.RequestedBlob != "" {
 		if len(request.RequestedBlob) != stream.BlobHashHexLength {
-			return nil, errors.Err("Invalid blob hash length")
+			return nil, "", errors.Err("Invalid blob hash length")
 		}
 
 		log.Debugln("Sending blob " + request.RequestedBlob[:8])
 
-		blob, trace, err = s.store.Get(request.RequestedBlob)
-		log.Debug(trace.String())
-		if errors.Is(err, store.ErrBlobNotFound) {
+		size, err := s.disk.Size(request.RequestedBlob)
+		if err != nil {
 			response.IncomingBlob = incomingBlob{
 				Error: err.Error(),
 			}
-		} else if err != nil {
-			return nil, err
 		} else {
 			response.IncomingBlob = incomingBlob{
-				BlobHash: reflector.BlobHash(blob),
-				Length:   len(blob),
+				BlobHash: request.RequestedBlob,
+				Length:   int(size),
 			}
-			metrics.MtrOutBytesTcp.Add(float64(len(blob)))
-			metrics.BlobDownloadCount.Inc()
-			metrics.PeerDownloadCount.Inc()
 		}
+		metrics.MtrOutBytesTcp.Add(float64(len(blob)))
+		metrics.BlobDownloadCount.Inc()
+		metrics.PeerDownloadCount.Inc()
 	}
 
 	respData, err := json.Marshal(response)
 	if err != nil {
-		return nil, err
+		return nil, "", err
 	}
 
-	return append(respData, blob...), nil
+	return respData, request.RequestedBlob, nil
 }
 
 func (s *Server) logError(e error) {
diff --git a/store/disk.go b/store/disk.go
index 233123a..3876204 100644
--- a/store/disk.go
+++ b/store/disk.go
@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net"
 	"os"
 	"path"
 	"time"
@@ -67,6 +68,14 @@ func (d *DiskStore) Has(hash string) (bool, error) {
 	return true, nil
 }
 
+func (d *DiskStore) Size(hash string) (int64, error) {
+	stat, err := os.Stat(d.path(hash))
+	if err != nil {
+		return 0, err
+	}
+	return stat.Size(), nil
+}
+
 // Get returns the blob or an error if the blob doesn't exist.
 func (d *DiskStore) Get(hash string) (stream.Blob, shared.BlobTrace, error) {
 	start := time.Now()
@@ -211,3 +220,15 @@ func (d *DiskStore) initOnce() error {
 // Shutdown shuts down the store gracefully
 func (d *DiskStore) Shutdown() {
 }
+
+func (d *DiskStore) Sendfile(hash string, conn net.Conn) error {
+	f, err := os.Open(d.path(hash))
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(conn, f)
+	if err != nil {
+		return err
+	}
+	return nil
+}
-- 
2.45.2