Integrate s3ChunkProducer to support chunk buffering

pkg/s3store/s3store.go

@@ -135,6 +135,11 @@ type S3Store struct {
 	// MaxObjectSize is the maximum size an S3 Object can have according to S3
 	// API specifications. See link above.
 	MaxObjectSize int64
+	// MaxBufferedParts is the number of additional parts that can be received from
+	// the client and stored on disk while a part is being uploaded to S3. This
+	// can help improve throughput by not blocking the client while tusd is
+	// communicating with the S3 API, which can have unpredictable latency.
+	MaxBufferedParts int
 }
 
 type S3API interface {
@@ -379,35 +384,26 @@ func (upload s3Upload) WriteChunk(ctx context.Context, offset int64, src io.Read
 		src = io.MultiReader(incompletePartFile, src)
 	}
 
-	for {
-		// Create a temporary file to store the part in it
-		file, err := ioutil.TempFile("", "tusd-s3-tmp-")
-		if err != nil {
-			return bytesUploaded, err
-		}
+	fileChan := make(chan *os.File, store.MaxBufferedParts)
+	doneChan := make(chan struct{})
+	defer close(doneChan)
+
+	chunkProducer := s3ChunkProducer{
+		done:  doneChan,
+		files: fileChan,
+		r:     src,
+	}
+	go chunkProducer.produce(optimalPartSize)
+
+	for file := range fileChan {
 		defer os.Remove(file.Name())
 		defer file.Close()
 
-		limitedReader := io.LimitReader(src, optimalPartSize)
-		n, err := io.Copy(file, limitedReader)
-
-		// If the HTTP PATCH request gets interrupted in the middle (e.g. because
-		// the user wants to pause the upload), Go's net/http returns an io.ErrUnexpectedEOF.
-		// However, for S3Store it's not important whether the stream has ended
-		// on purpose or accidentally. Therefore, we ignore this error to not
-		// prevent the remaining chunk to be stored on S3.
-		if err == io.ErrUnexpectedEOF {
-			err = nil
-		}
-
-		// io.Copy does not return io.EOF, so we not have to handle it differently.
+		stat, err := file.Stat()
 		if err != nil {
-			return bytesUploaded, err
-		}
-		// If io.Copy is finished reading, it will always return (0, nil).
-		if n == 0 {
-			return (bytesUploaded - incompletePartSize), nil
+			return 0, err
 		}
+		n := stat.Size()
 
 		// Seek to the beginning of the file
 		file.Seek(0, 0)
@@ -438,6 +434,8 @@ func (upload s3Upload) WriteChunk(ctx context.Context, offset int64, src io.Read
 		bytesUploaded += n
 		nextPartNum += 1
 	}
+
+	return bytesUploaded - incompletePartSize, chunkProducer.err
 }
 
 func (upload *s3Upload) GetInfo(ctx context.Context) (info handler.FileInfo, err error) {