wrap buffered writer around filewriter

benchmarks added to filewriter_test, demonstrate buffered
version is ~5x faster on my hardware.
Signed-off-by: David Lawrence <david.lawrence@docker.com> (github: endophage)

docs/storage/filewriter.go

@@ -1,6 +1,7 @@
 package storage
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
 	"io"
@@ -9,6 +10,10 @@ import (
 	storagedriver "github.com/docker/distribution/registry/storage/driver"
 )
 
+const (
+	fileWriterBufferSize = 5 << 20
+)
+
 // fileWriter implements a remote file writer backed by a storage driver.
 type fileWriter struct {
 	driver storagedriver.StorageDriver
@@ -22,6 +27,11 @@ type fileWriter struct {
 	err    error // terminal error, if set, reader is closed
 }
 
+type bufferedFileWriter struct {
+	fileWriter
+	bw *bufio.Writer
+}
+
 // fileWriterInterface makes the desired io compliant interface that the
 // filewriter should implement.
 type fileWriterInterface interface {
@@ -35,7 +45,7 @@ var _ fileWriterInterface = &fileWriter{}
 
 // newFileWriter returns a prepared fileWriter for the driver and path. This
 // could be considered similar to an "open" call on a regular filesystem.
-func newFileWriter(driver storagedriver.StorageDriver, path string) (*fileWriter, error) {
+func newFileWriter(driver storagedriver.StorageDriver, path string) (*bufferedFileWriter, error) {
 	fw := fileWriter{
 		driver: driver,
 		path:   path,
@@ -56,7 +66,42 @@ func newFileWriter(driver storagedriver.StorageDriver, path string) (*fileWriter
 		fw.size = fi.Size()
 	}
 
-	return &fw, nil
+	buffered := bufferedFileWriter{
+		fileWriter: fw,
+	}
+	buffered.bw = bufio.NewWriterSize(&buffered.fileWriter, fileWriterBufferSize)
+
+	return &buffered, nil
+}
+
+// wraps the fileWriter.Write method to buffer small writes
+func (bfw *bufferedFileWriter) Write(p []byte) (int, error) {
+	return bfw.bw.Write(p)
+}
+
+// wraps fileWriter.Close to ensure the buffer is flushed
+// before we close the writer.
+func (bfw *bufferedFileWriter) Close() (err error) {
+	if err = bfw.Flush(); err != nil {
+		return err
+	}
+	err = bfw.fileWriter.Close()
+	return err
+}
+
+// wraps fileWriter.Seek to ensure offset is handled
+// correctly in respect to pending data in the buffer
+func (bfw *bufferedFileWriter) Seek(offset int64, whence int) (int64, error) {
+	if err := bfw.Flush(); err != nil {
+		return 0, err
+	}
+	return bfw.fileWriter.Seek(offset, whence)
+}
+
+// wraps bufio.Writer.Flush to allow intermediate flushes
+// of the bufferedFileWriter
+func (bfw *bufferedFileWriter) Flush() error {
+	return bfw.bw.Flush()
 }
 
 // Write writes the buffer p at the current write offset.
@@ -108,6 +153,9 @@ func (fw *fileWriter) Seek(offset int64, whence int) (int64, error) {
 }
 
 // Close closes the fileWriter for writing.
+// Calling it once is valid and correct and it will
+// return a nil error. Calling it subsequent times will
+// detect that fw.err has been set and will return the error.
 func (fw *fileWriter) Close() error {
 	if fw.err != nil {
 		return fw.err
@@ -115,7 +163,7 @@ func (fw *fileWriter) Close() error {
 
 	fw.err = fmt.Errorf("filewriter@%v: closed", fw.path)
 
-	return fw.err
+	return nil
 }
 
 // readFromAt writes to fw from r at the specified offset. If offset is less

docs/storage/filewriter_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 
 	"github.com/docker/distribution/digest"
+	storagedriver "github.com/docker/distribution/registry/storage/driver"
 	"github.com/docker/distribution/registry/storage/driver/inmemory"
 )
 
@@ -42,6 +43,7 @@ func TestSimpleWrite(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected error writing content: %v", err)
 	}
+	fw.Flush()
 
 	if n != len(content) {
 		t.Fatalf("unexpected write length: %d != %d", n, len(content))
@@ -146,3 +148,99 @@ func TestSimpleWrite(t *testing.T) {
 		t.Fatalf("unable to verify write data")
 	}
 }
+
+func TestBufferedFileWriter(t *testing.T) {
+	writer, err := newFileWriter(inmemory.New(), "/random")
+
+	if err != nil {
+		t.Fatalf("Failed to initialize bufferedFileWriter: %v", err.Error())
+	}
+
+	// write one byte and ensure the offset hasn't been incremented.
+	// offset will only get incremented when the buffer gets flushed
+	short := []byte{byte(1)}
+
+	writer.Write(short)
+
+	if writer.offset > 0 {
+		t.Fatalf("WriteStream called prematurely")
+	}
+
+	// write enough data to cause the buffer to flush and confirm
+	// the offset has been incremented
+	long := make([]byte, fileWriterBufferSize)
+	_, err = rand.Read(long)
+	if err != nil {
+		t.Fatalf("unexpected error building random data: %v", err)
+	}
+	for i := range long {
+		long[i] = byte(i)
+	}
+	writer.Write(long)
+	writer.Close()
+	if writer.offset != (fileWriterBufferSize + 1) {
+		t.Fatalf("WriteStream not called when buffer capacity reached")
+	}
+}
+
+func BenchmarkFileWriter(b *testing.B) {
+	b.StopTimer() // not sure how long setup above will take
+	for i := 0; i < b.N; i++ {
+		// Start basic fileWriter initialization
+		fw := fileWriter{
+			driver: inmemory.New(),
+			path:   "/random",
+		}
+
+		if fi, err := fw.driver.Stat(fw.path); err != nil {
+			switch err := err.(type) {
+			case storagedriver.PathNotFoundError:
+				// ignore, offset is zero
+			default:
+				b.Fatalf("Failed to initialize fileWriter: %v", err.Error())
+			}
+		} else {
+			if fi.IsDir() {
+				b.Fatalf("Cannot write to a directory")
+			}
+
+			fw.size = fi.Size()
+		}
+
+		randomBytes := make([]byte, 1<<20)
+		_, err := rand.Read(randomBytes)
+		if err != nil {
+			b.Fatalf("unexpected error building random data: %v", err)
+		}
+		// End basic file writer initialization
+
+		b.StartTimer()
+		for j := 0; j < 100; j++ {
+			fw.Write(randomBytes)
+		}
+		b.StopTimer()
+	}
+}
+
+func BenchmarkBufferedFileWriter(b *testing.B) {
+	b.StopTimer() // not sure how long setup above will take
+	for i := 0; i < b.N; i++ {
+		bfw, err := newFileWriter(inmemory.New(), "/random")
+
+		if err != nil {
+			b.Fatalf("Failed to initialize bufferedFileWriter: %v", err.Error())
+		}
+
+		randomBytes := make([]byte, 1<<20)
+		_, err = rand.Read(randomBytes)
+		if err != nil {
+			b.Fatalf("unexpected error building random data: %v", err)
+		}
+
+		b.StartTimer()
+		for j := 0; j < 100; j++ {
+			bfw.Write(randomBytes)
+		}
+		b.StopTimer()
+	}
+}

docs/storage/layerstore.go

@@ -142,7 +142,7 @@ func (ls *layerStore) newLayerUpload(uuid, path string, startedAt time.Time) (di
 		layerStore:         ls,
 		uuid:               uuid,
 		startedAt:          startedAt,
-		fileWriter: *fw,
+		bufferedFileWriter: *fw,
 	}, nil
 }
 

docs/storage/layerupload.go

@@ -22,7 +22,9 @@ type layerUploadController struct {
 	uuid      string
 	startedAt time.Time
 
-	fileWriter
+	// implementes io.WriteSeeker, io.ReaderFrom and io.Closer to satisy
+	// LayerUpload Interface
+	bufferedFileWriter
 }
 
 var _ distribution.LayerUpload = &layerUploadController{}
@@ -42,6 +44,12 @@ func (luc *layerUploadController) StartedAt() time.Time {
 // format <algorithm>:<hex digest>.
 func (luc *layerUploadController) Finish(digest digest.Digest) (distribution.Layer, error) {
 	ctxu.GetLogger(luc.layerStore.repository.ctx).Debug("(*layerUploadController).Finish")
+
+	err := luc.bufferedFileWriter.Close()
+	if err != nil {
+		return nil, err
+	}
+
 	canonical, err := luc.validateLayer(digest)
 	if err != nil {
 		return nil, err
@@ -103,7 +111,7 @@ func (luc *layerUploadController) validateLayer(dgst digest.Digest) (digest.Dige
 	// then only have to fetch the difference.
 
 	// Read the file from the backend driver and validate it.
-	fr, err := newFileReader(luc.fileWriter.driver, luc.path)
+	fr, err := newFileReader(luc.bufferedFileWriter.driver, luc.path)
 	if err != nil {
 		return "", err
 	}