Push uploader control flow into objectstore package

changelogs/unreleased/jv-uploader-readerfrom.yml

+---
+title: Push uploader control flow into objectstore package
+merge_request: 608
+author:
+type: other

internal/filestore/file_handler.go

@@ -8,6 +8,7 @@ import (
 	"io/ioutil"
 	"os"
 	"strconv"
+	"time"
 
 	"github.com/dgrijalva/jwt-go"
 
@@ -98,38 +99,28 @@ func (fh *FileHandler) GitLabFinalizeFields(prefix string) (map[string]string, e
 	return data, nil
 }
 
-// Upload represents a destination where we store an upload
-type uploadWriter interface {
-	io.WriteCloser
-	CloseWithError(error) error
-	ETag() string
+type consumer interface {
+	Consume(context.Context, io.Reader, time.Time) (int64, error)
 }
 
 // SaveFileFromReader persists the provided reader content to all the location specified in opts. A cleanup will be performed once ctx is Done
 // Make sure the provided context will not expire before finalizing upload with GitLab Rails.
 func SaveFileFromReader(ctx context.Context, reader io.Reader, size int64, opts *SaveFileOpts) (fh *FileHandler, err error) {
-	var uploadWriter uploadWriter
+	var uploadDestination consumer
 	fh = &FileHandler{
 		Name:      opts.TempFilePrefix,
 		RemoteID:  opts.RemoteID,
 		RemoteURL: opts.RemoteURL,
 	}
 	hashes := newMultiHash()
-	writers := []io.Writer{hashes.Writer}
-	defer func() {
-		for _, w := range writers {
-			if closer, ok := w.(io.WriteCloser); ok {
-				closer.Close()
-			}
-		}
-	}()
+	reader = io.TeeReader(reader, hashes.Writer)
 
 	var clientMode string
 
 	switch {
 	case opts.IsLocal():
 		clientMode = "local"
-		uploadWriter, err = fh.uploadLocalFile(ctx, opts)
+		uploadDestination, err = fh.uploadLocalFile(ctx, opts)
 	case opts.UseWorkhorseClientEnabled() && opts.ObjectStorageConfig.IsGoCloud():
 		clientMode = fmt.Sprintf("go_cloud:%s", opts.ObjectStorageConfig.Provider)
 		p := &objectstore.GoCloudObjectParams{
@@ -137,38 +128,31 @@ func SaveFileFromReader(ctx context.Context, reader io.Reader, size int64, opts
 			Mux:        opts.ObjectStorageConfig.URLMux,
 			BucketURL:  opts.ObjectStorageConfig.GoCloudConfig.URL,
 			ObjectName: opts.RemoteTempObjectID,
-			Deadline:   opts.Deadline,
 		}
-		uploadWriter, err = objectstore.NewGoCloudObject(p)
+		uploadDestination, err = objectstore.NewGoCloudObject(p)
 	case opts.UseWorkhorseClientEnabled() && opts.ObjectStorageConfig.IsAWS() && opts.ObjectStorageConfig.IsValid():
 		clientMode = "s3"
-		uploadWriter, err = objectstore.NewS3Object(
-			ctx,
+		uploadDestination, err = objectstore.NewS3Object(
 			opts.RemoteTempObjectID,
 			opts.ObjectStorageConfig.S3Credentials,
 			opts.ObjectStorageConfig.S3Config,
-			opts.Deadline,
 		)
 	case opts.IsMultipart():
 		clientMode = "multipart"
-		uploadWriter, err = objectstore.NewMultipart(
-			ctx,
+		uploadDestination, err = objectstore.NewMultipart(
 			opts.PresignedParts,
 			opts.PresignedCompleteMultipart,
 			opts.PresignedAbortMultipart,
 			opts.PresignedDelete,
 			opts.PutHeaders,
-			opts.Deadline,
 			opts.PartSize,
 		)
 	default:
 		clientMode = "http"
-		uploadWriter, err = objectstore.NewObject(
-			ctx,
+		uploadDestination, err = objectstore.NewObject(
 			opts.PresignedPut,
 			opts.PresignedDelete,
 			opts.PutHeaders,
-			opts.Deadline,
 			size,
 		)
 	}
@@ -177,34 +161,22 @@ func SaveFileFromReader(ctx context.Context, reader io.Reader, size int64, opts
 		return nil, err
 	}
 
-	writers = append(writers, uploadWriter)
-
-	defer func() {
-		if err != nil {
-			uploadWriter.CloseWithError(err)
-		}
-	}()
-
 	if opts.MaximumSize > 0 {
 		if size > opts.MaximumSize {
 			return nil, SizeError(fmt.Errorf("the upload size %d is over maximum of %d bytes", size, opts.MaximumSize))
 		}
 
-		// We allow to read an extra byte to check later if we exceed the max size
-		reader = &io.LimitedReader{R: reader, N: opts.MaximumSize + 1}
+		reader = &hardLimitReader{r: reader, n: opts.MaximumSize}
 	}
 
-	multiWriter := io.MultiWriter(writers...)
-	fh.Size, err = io.Copy(multiWriter, reader)
+	fh.Size, err = uploadDestination.Consume(ctx, reader, opts.Deadline)
 	if err != nil {
+		if err == objectstore.ErrNotEnoughParts {
+			err = ErrEntityTooLarge
+		}
 		return nil, err
 	}
 
-	if opts.MaximumSize > 0 && fh.Size > opts.MaximumSize {
-		// An extra byte was read thus exceeding the max size
-		return nil, ErrEntityTooLarge
-	}
-
 	if size != -1 && size != fh.Size {
 		return nil, SizeError(fmt.Errorf("expected %d bytes but got only %d", size, fh.Size))
 	}
@@ -226,25 +198,11 @@ func SaveFileFromReader(ctx context.Context, reader io.Reader, size int64, opts
 	}
 
 	logger.Info("saved file")
-
 	fh.hashes = hashes.finish()
-
-	// we need to close the writer in order to get ETag header
-	err = uploadWriter.Close()
-	if err != nil {
-		if err == objectstore.ErrNotEnoughParts {
-			return nil, ErrEntityTooLarge
-		}
-		return nil, err
-	}
-
-	etag := uploadWriter.ETag()
-	fh.hashes["etag"] = etag
-
-	return fh, err
+	return fh, nil
 }
 
-func (fh *FileHandler) uploadLocalFile(ctx context.Context, opts *SaveFileOpts) (uploadWriter, error) {
+func (fh *FileHandler) uploadLocalFile(ctx context.Context, opts *SaveFileOpts) (consumer, error) {
 	// make sure TempFolder exists
 	err := os.MkdirAll(opts.LocalTempPath, 0700)
 	if err != nil {
@@ -262,13 +220,19 @@ func (fh *FileHandler) uploadLocalFile(ctx context.Context, opts *SaveFileOpts)
 	}()
 
 	fh.LocalPath = file.Name()
-	return &nopUpload{file}, nil
+	return &localUpload{file}, nil
 }
 
-type nopUpload struct{ io.WriteCloser }
+type localUpload struct{ io.WriteCloser }
 
-func (nop *nopUpload) CloseWithError(error) error { return nop.Close() }
-func (nop *nopUpload) ETag() string               { return "" }
+func (loc *localUpload) Consume(_ context.Context, r io.Reader, _ time.Time) (int64, error) {
+	n, err := io.Copy(loc.WriteCloser, r)
+	errClose := loc.Close()
+	if err == nil {
+		err = errClose
+	}
+	return n, err
+}
 
 // SaveFileFromDisk open the local file fileName and calls SaveFileFromReader
 func SaveFileFromDisk(ctx context.Context, fileName string, opts *SaveFileOpts) (fh *FileHandler, err error) {

internal/filestore/file_handler_test.go

@@ -413,5 +413,4 @@ func checkFileHandlerWithFields(t *testing.T, fh *filestore.FileHandler, fields
 	require.Equal(t, test.ObjectSHA1, fields[key("sha1")])
 	require.Equal(t, test.ObjectSHA256, fields[key("sha256")])
 	require.Equal(t, test.ObjectSHA512, fields[key("sha512")])
-	require.Contains(t, fields, key("etag"))
 }

internal/filestore/reader.go

+package filestore
+
+import "io"
+
+type hardLimitReader struct {
+	r io.Reader
+	n int64
+}
+
+func (h *hardLimitReader) Read(p []byte) (int, error) {
+	nRead, err := h.r.Read(p)
+	h.n -= int64(nRead)
+	if h.n < 0 {
+		err = ErrEntityTooLarge
+	}
+	return nRead, err
+}

internal/filestore/reader_test.go

+package filestore
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strings"
+	"testing"
+	"testing/iotest"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestHardLimitReader(t *testing.T) {
+	const text = "hello world"
+	r := iotest.OneByteReader(
+		&hardLimitReader{
+			r: strings.NewReader(text),
+			n: int64(len(text)),
+		},
+	)
+
+	out, err := ioutil.ReadAll(r)
+	require.NoError(t, err)
+	require.Equal(t, text, string(out))
+}
+
+func TestHardLimitReaderFail(t *testing.T) {
+	const text = "hello world"
+
+	for bufSize := len(text) / 2; bufSize < len(text)*2; bufSize++ {
+		t.Run(fmt.Sprintf("bufsize:%d", bufSize), func(t *testing.T) {
+			r := &hardLimitReader{
+				r: iotest.DataErrReader(strings.NewReader(text)),
+				n: int64(len(text)) - 1,
+			}
+			buf := make([]byte, bufSize)
+
+			var err error
+			for i := 0; err == nil && i < 1000; i++ {
+				_, err = r.Read(buf)
+			}
+
+			require.Equal(t, ErrEntityTooLarge, err)
+		})
+	}
+}

internal/objectstore/gocloud_object.go

@@ -15,7 +15,7 @@ type GoCloudObject struct {
 	mux        *blob.URLMux
 	bucketURL  string
 	objectName string
-	uploader
+	*uploader
 }
 
 type GoCloudObjectParams struct {
@@ -23,7 +23,6 @@ type GoCloudObjectParams struct {
 	Mux        *blob.URLMux
 	BucketURL  string
 	ObjectName string
-	Deadline   time.Time
 }
 
 func NewGoCloudObject(p *GoCloudObjectParams) (*GoCloudObject, error) {
@@ -40,8 +39,6 @@ func NewGoCloudObject(p *GoCloudObjectParams) (*GoCloudObject, error) {
 	}
 
 	o.uploader = newUploader(o)
-	o.Execute(p.Ctx, p.Deadline)
-
 	return o, nil
 }
 

internal/objectstore/gocloud_object_test.go

@@ -3,7 +3,6 @@ package objectstore_test
 import (
 	"context"
 	"fmt"
-	"io"
 	"strings"
 	"testing"
 	"time"
@@ -24,20 +23,16 @@ func TestGoCloudObjectUpload(t *testing.T) {
 
 	objectName := "test.png"
 	testURL := "azuretest://azure.example.com/test-container"
-	p := &objectstore.GoCloudObjectParams{Ctx: ctx, Mux: mux, BucketURL: testURL, ObjectName: objectName, Deadline: deadline}
+	p := &objectstore.GoCloudObjectParams{Ctx: ctx, Mux: mux, BucketURL: testURL, ObjectName: objectName}
 	object, err := objectstore.NewGoCloudObject(p)
 	require.NotNil(t, object)
 	require.NoError(t, err)
 
 	// copy data
-	n, err := io.Copy(object, strings.NewReader(test.ObjectContent))
+	n, err := object.Consume(ctx, strings.NewReader(test.ObjectContent), deadline)
 	require.NoError(t, err)
 	require.Equal(t, test.ObjectSize, n, "Uploaded file mismatch")
 
-	// close HTTP stream
-	err = object.Close()
-	require.NoError(t, err)
-
 	bucket, err := mux.OpenBucket(ctx, testURL)
 	require.NoError(t, err)
 

internal/objectstore/multipart.go

@@ -10,7 +10,6 @@ import (
 	"io/ioutil"
 	"net/http"
 	"os"
-	"time"
 
 	"gitlab.com/gitlab-org/labkit/log"
 	"gitlab.com/gitlab-org/labkit/mask"
@@ -33,13 +32,13 @@ type Multipart struct {
 	partSize   int64
 	etag       string
 
-	uploader
+	*uploader
 }
 
 // NewMultipart provides Multipart pointer that can be used for uploading. Data written will be split buffered on disk up to size bytes
 // then uploaded with S3 Upload Part. Once Multipart is Closed a final call to CompleteMultipartUpload will be sent.
 // In case of any error a call to AbortMultipartUpload will be made to cleanup all the resources
-func NewMultipart(ctx context.Context, partURLs []string, completeURL, abortURL, deleteURL string, putHeaders map[string]string, deadline time.Time, partSize int64) (*Multipart, error) {
+func NewMultipart(partURLs []string, completeURL, abortURL, deleteURL string, putHeaders map[string]string, partSize int64) (*Multipart, error) {
 	m := &Multipart{
 		PartURLs:    partURLs,
 		CompleteURL: completeURL,
@@ -50,8 +49,6 @@ func NewMultipart(ctx context.Context, partURLs []string, completeURL, abortURL,
 	}
 
 	m.uploader = newUploader(m)
-	m.Execute(ctx, deadline)
-
 	return m, nil
 }
 
@@ -109,7 +106,7 @@ func (m *Multipart) readAndUploadOnePart(ctx context.Context, partURL string, pu
 
 	n, err := io.Copy(file, src)
 	if err != nil {
-		return nil, fmt.Errorf("write part %d to disk: %v", partNumber, err)
+		return nil, err
 	}
 	if n == 0 {
 		return nil, nil
@@ -132,18 +129,15 @@ func (m *Multipart) uploadPart(ctx context.Context, url string, headers map[stri
 		return "", fmt.Errorf("missing deadline")
 	}
 
-	part, err := newObject(ctx, url, "", headers, deadline, size, false)
+	part, err := newObject(url, "", headers, size, false)
 	if err != nil {
 		return "", err
 	}
 
-	_, err = io.CopyN(part, body, size)
-	if err != nil {
-		return "", err
-	}
-
-	err = part.Close()
-	if err != nil {
+	if n, err := part.Consume(ctx, io.LimitReader(body, size), deadline); err != nil || n < size {
+		if err == nil {
+			err = io.ErrUnexpectedEOF
+		}
 		return "", err
 	}
 

internal/objectstore/multipart_test.go

@@ -48,19 +48,17 @@ func TestMultipartUploadWithUpcaseETags(t *testing.T) {
 
 	deadline := time.Now().Add(testTimeout)
 
-	m, err := objectstore.NewMultipart(ctx,
+	m, err := objectstore.NewMultipart(
 		[]string{ts.URL},    // a single presigned part URL
 		ts.URL,              // the complete multipart upload URL
 		"",                  // no abort
 		"",                  // no delete
 		map[string]string{}, // no custom headers
-		deadline,
-		test.ObjectSize) // parts size equal to the whole content. Only 1 part
+		test.ObjectSize)     // parts size equal to the whole content. Only 1 part
 	require.NoError(t, err)
 
-	_, err = m.Write([]byte(test.ObjectContent))
+	_, err = m.Consume(ctx, strings.NewReader(test.ObjectContent), deadline)
 	require.NoError(t, err)
-	require.NoError(t, m.Close())
 	require.Equal(t, 1, putCnt, "1 part expected")
 	require.Equal(t, 1, postCnt, "1 complete multipart upload expected")
 }

internal/objectstore/object.go

@@ -47,17 +47,17 @@ type Object struct {
 	etag       string
 	metrics    bool
 
-	uploader
+	*uploader
 }
 
 type StatusCodeError error
 
 // NewObject opens an HTTP connection to Object Store and returns an Object pointer that can be used for uploading.
-func NewObject(ctx context.Context, putURL, deleteURL string, putHeaders map[string]string, deadline time.Time, size int64) (*Object, error) {
-	return newObject(ctx, putURL, deleteURL, putHeaders, deadline, size, true)
+func NewObject(putURL, deleteURL string, putHeaders map[string]string, size int64) (*Object, error) {
+	return newObject(putURL, deleteURL, putHeaders, size, true)
 }
 
-func newObject(ctx context.Context, putURL, deleteURL string, putHeaders map[string]string, deadline time.Time, size int64, metrics bool) (*Object, error) {
+func newObject(putURL, deleteURL string, putHeaders map[string]string, size int64, metrics bool) (*Object, error) {
 	o := &Object{
 		putURL:     putURL,
 		deleteURL:  deleteURL,
@@ -66,9 +66,7 @@ func newObject(ctx context.Context, putURL, deleteURL string, putHeaders map[str
 		metrics:    metrics,
 	}
 
-	o.uploader = newMD5Uploader(o, metrics)
-	o.Execute(ctx, deadline)
-
+	o.uploader = newETagCheckUploader(o, metrics)
 	return o, nil
 }
 

internal/objectstore/object_test.go

@@ -35,18 +35,14 @@ func testObjectUploadNoErrors(t *testing.T, startObjectStore osFactory, useDelet
 	defer cancel()
 
 	deadline := time.Now().Add(testTimeout)
-	object, err := objectstore.NewObject(ctx, objectURL, deleteURL, putHeaders, deadline, test.ObjectSize)
+	object, err := objectstore.NewObject(objectURL, deleteURL, putHeaders, test.ObjectSize)
 	require.NoError(t, err)
 
 	// copy data
-	n, err := io.Copy(object, strings.NewReader(test.ObjectContent))
+	n, err := object.Consume(ctx, strings.NewReader(test.ObjectContent), deadline)
 	require.NoError(t, err)
 	require.Equal(t, test.ObjectSize, n, "Uploaded file mismatch")
 
-	// close HTTP stream
-	err = object.Close()
-	require.NoError(t, err)
-
 	require.Equal(t, contentType, osStub.GetHeader(test.ObjectPath, "Content-Type"))
 
 	// Checking MD5 extraction
@@ -107,12 +103,10 @@ func TestObjectUpload404(t *testing.T) {
 
 	deadline := time.Now().Add(testTimeout)
 	objectURL := ts.URL + test.ObjectPath
-	object, err := objectstore.NewObject(ctx, objectURL, "", map[string]string{}, deadline, test.ObjectSize)
+	object, err := objectstore.NewObject(objectURL, "", map[string]string{}, test.ObjectSize)
 	require.NoError(t, err)
-	_, err = io.Copy(object, strings.NewReader(test.ObjectContent))
+	_, err = object.Consume(ctx, strings.NewReader(test.ObjectContent), deadline)
 
-	require.NoError(t, err)
-	err = object.Close()
 	require.Error(t, err)
 	_, isStatusCodeError := err.(objectstore.StatusCodeError)
 	require.True(t, isStatusCodeError, "Should fail with StatusCodeError")
@@ -152,13 +146,10 @@ func TestObjectUploadBrokenConnection(t *testing.T) {
 
 	deadline := time.Now().Add(testTimeout)
 	objectURL := ts.URL + test.ObjectPath
-	object, err := objectstore.NewObject(ctx, objectURL, "", map[string]string{}, deadline, -1)
+	object, err := objectstore.NewObject(objectURL, "", map[string]string{}, -1)
 	require.NoError(t, err)
 
-	_, copyErr := io.Copy(object, &endlessReader{})
+	_, copyErr := object.Consume(ctx, &endlessReader{}, deadline)
 	require.Error(t, copyErr)
 	require.NotEqual(t, io.ErrClosedPipe, copyErr, "We are shadowing the real error")
-
-	closeErr := object.Close()
-	require.Equal(t, copyErr, closeErr)
 }

internal/objectstore/s3_object.go

@@ -19,10 +19,10 @@ type S3Object struct {
 	objectName  string
 	uploaded    bool
 
-	uploader
+	*uploader
 }
 
-func NewS3Object(ctx context.Context, objectName string, s3Credentials config.S3Credentials, s3Config config.S3Config, deadline time.Time) (*S3Object, error) {
+func NewS3Object(objectName string, s3Credentials config.S3Credentials, s3Config config.S3Config) (*S3Object, error) {
 	o := &S3Object{
 		credentials: s3Credentials,
 		config:      s3Config,
@@ -30,8 +30,6 @@ func NewS3Object(ctx context.Context, objectName string, s3Credentials config.S3
 	}
 
 	o.uploader = newUploader(o)
-	o.Execute(ctx, deadline)
-
 	return o, nil
 }
 

internal/objectstore/s3_object_test.go

@@ -3,7 +3,6 @@ package objectstore_test
 import (
 	"context"
 	"fmt"
-	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -44,18 +43,14 @@ func TestS3ObjectUpload(t *testing.T) {
 			objectName := filepath.Join(tmpDir, "s3-test-data")
 			ctx, cancel := context.WithCancel(context.Background())
 
-			object, err := objectstore.NewS3Object(ctx, objectName, creds, config, deadline)
+			object, err := objectstore.NewS3Object(objectName, creds, config)
 			require.NoError(t, err)
 
 			// copy data
-			n, err := io.Copy(object, strings.NewReader(test.ObjectContent))
+			n, err := object.Consume(ctx, strings.NewReader(test.ObjectContent), deadline)
 			require.NoError(t, err)
 			require.Equal(t, test.ObjectSize, n, "Uploaded file mismatch")
 
-			// close HTTP stream
-			err = object.Close()
-			require.NoError(t, err)
-
 			test.S3ObjectExists(t, sess, config, objectName, test.ObjectContent)
 			test.CheckS3Metadata(t, sess, config, objectName)
 
@@ -107,17 +102,14 @@ func TestConcurrentS3ObjectUpload(t *testing.T) {
 			ctx, cancel := context.WithCancel(context.Background())
 			defer cancel()
 
-			object, err := objectstore.NewS3Object(ctx, objectName, creds, config, deadline)
+			object, err := objectstore.NewS3Object(objectName, creds, config)
 			require.NoError(t, err)
 
 			// copy data
-			n, err := io.Copy(object, strings.NewReader(test.ObjectContent))
+			n, err := object.Consume(ctx, strings.NewReader(test.ObjectContent), deadline)
 			require.NoError(t, err)
 			require.Equal(t, test.ObjectSize, n, "Uploaded file mismatch")
 
-			// close HTTP stream
-			require.NoError(t, object.Close())
-
 			test.S3ObjectExists(t, sess, config, objectName, test.ObjectContent)
 			wg.Done()
 		}(i)
@@ -139,7 +131,7 @@ func TestS3ObjectUploadCancel(t *testing.T) {
 
 	objectName := filepath.Join(tmpDir, "s3-test-data")
 
-	object, err := objectstore.NewS3Object(ctx, objectName, creds, config, deadline)
+	object, err := objectstore.NewS3Object(objectName, creds, config)
 
 	require.NoError(t, err)
 
@@ -147,6 +139,6 @@ func TestS3ObjectUploadCancel(t *testing.T) {
 	// we handle this gracefully.
 	cancel()
 
-	_, err = io.Copy(object, strings.NewReader(test.ObjectContent))
+	_, err = object.Consume(ctx, strings.NewReader(test.ObjectContent), deadline)
 	require.Error(t, err)
 }

internal/objectstore/uploader.go

@@ -8,177 +8,89 @@ import (
 	"hash"
 	"io"
 	"strings"
-	"sync"
 	"time"
 
 	"gitlab.com/gitlab-org/labkit/log"
 )
 
-// uploader is an io.WriteCloser that can be used as write end of the uploading pipe.
+// uploader consumes an io.Reader and uploads it using a pluggable uploadStrategy.
 type uploader struct {
-	// etag is the object storage provided checksum
-	etag string
-
-	// md5 is an optional hasher for calculating md5 on the fly
-	md5 hash.Hash
-
-	w io.Writer
-
-	// uploadError is the last error occourred during upload
-	uploadError error
-	// ctx is the internal context bound to the upload request
-	ctx context.Context
-
-	pr       *io.PipeReader
-	pw       *io.PipeWriter
 	strategy uploadStrategy
-	metrics  bool
 
-	// closeOnce is used to prevent multiple calls to pw.Close
-	// which may result to Close overriding the error set by CloseWithError
-	// Bug fixed in v1.14: https://github.com/golang/go/commit/f45eb9ff3c96dfd951c65d112d033ed7b5e02432
-	closeOnce sync.Once
-}
+	// In the case of S3 uploads, we have a multipart upload which
+	// instantiates uploads for the individual parts. We don't want to
+	// increment metrics for the individual parts, so that is why we have
+	// this boolean flag.
+	metrics bool
 
-func newUploader(strategy uploadStrategy) uploader {
-	pr, pw := io.Pipe()
-	return uploader{w: pw, pr: pr, pw: pw, strategy: strategy, metrics: true}
+	// With S3 we compare the MD5 of the data we sent with the ETag returned
+	// by the object storage server.
+	checkETag bool
 }
 
-func newMD5Uploader(strategy uploadStrategy, metrics bool) uploader {
-	pr, pw := io.Pipe()
-	hasher := md5.New()
-	mw := io.MultiWriter(pw, hasher)
-	return uploader{w: mw, pr: pr, pw: pw, md5: hasher, strategy: strategy, metrics: metrics}
+func newUploader(strategy uploadStrategy) *uploader {
+	return &uploader{strategy: strategy, metrics: true}
 }
 
-// Close implements the standard io.Closer interface: it closes the http client request.
-// This method will also wait for the connection to terminate and return any error occurred during the upload
-func (u *uploader) Close() error {
-	var closeError error
-	u.closeOnce.Do(func() {
-		closeError = u.pw.Close()
-	})
-	if closeError != nil {
-		return closeError
-	}
-
-	<-u.ctx.Done()
-
-	if err := u.ctx.Err(); err == context.DeadlineExceeded {
-		return err
-	}
-
-	return u.uploadError
+func newETagCheckUploader(strategy uploadStrategy, metrics bool) *uploader {
+	return &uploader{strategy: strategy, metrics: metrics, checkETag: true}
 }
 
-func (u *uploader) CloseWithError(err error) error {
-	u.closeOnce.Do(func() {
-		u.pw.CloseWithError(err)
-	})
-
-	return nil
-}
+func hexString(h hash.Hash) string { return hex.EncodeToString(h.Sum(nil)) }
 
-func (u *uploader) Write(p []byte) (int, error) {
-	return u.w.Write(p)
-}
-
-func (u *uploader) md5Sum() string {
-	if u.md5 == nil {
-		return ""
-	}
-
-	checksum := u.md5.Sum(nil)
-	return hex.EncodeToString(checksum)
-}
-
-// ETag returns the checksum of the uploaded object returned by the ObjectStorage provider via ETag Header.
-// This method will wait until upload context is done before returning.
-func (u *uploader) ETag() string {
-	<-u.ctx.Done()
-
-	return u.etag
-}
-
-func (u *uploader) Execute(ctx context.Context, deadline time.Time) {
+// Consume reads the reader until it reaches EOF or an error. It spawns a
+// goroutine that waits for outerCtx to be done, after which the remote
+// file is deleted. The deadline applies to the upload performed inside
+// Consume, not to outerCtx.
+func (u *uploader) Consume(outerCtx context.Context, reader io.Reader, deadline time.Time) (_ int64, err error) {
 	if u.metrics {
 		objectStorageUploadsOpen.Inc()
+		defer func(started time.Time) {
+			objectStorageUploadsOpen.Dec()
+			objectStorageUploadTime.Observe(time.Since(started).Seconds())
+			if err != nil {
+				objectStorageUploadRequestsRequestFailed.Inc()
+			}
+		}(time.Now())
 	}
-	uploadCtx, cancelFn := context.WithDeadline(ctx, deadline)
-	u.ctx = uploadCtx
-
-	if u.metrics {
-		go u.trackUploadTime()
-	}
-
-	uploadDone := make(chan struct{})
-	go u.cleanup(ctx, uploadDone)
-	go func() {
-		defer cancelFn()
-		defer close(uploadDone)
-
-		if u.metrics {
-			defer objectStorageUploadsOpen.Dec()
-		}
-		defer func() {
-			// This will be returned as error to the next write operation on the pipe
-			u.pr.CloseWithError(u.uploadError)
-		}()
 
-		err := u.strategy.Upload(uploadCtx, u.pr)
+	defer func() {
+		// We do this mainly to abort S3 multipart uploads: it is not enough to
+		// "delete" them.
 		if err != nil {
-			u.uploadError = err
-			if u.metrics {
-				objectStorageUploadRequestsRequestFailed.Inc()
-			}
-			return
+			u.strategy.Abort()
 		}
+	}()
 
-		u.etag = u.strategy.ETag()
-
-		if u.md5 != nil {
-			err := compareMD5(u.md5Sum(), u.etag)
-			if err != nil {
-				log.ContextLogger(ctx).WithError(err).Error("error comparing MD5 checksum")
-
-				u.uploadError = err
-				if u.metrics {
-					objectStorageUploadRequestsRequestFailed.Inc()
-				}
-			}
-		}
+	go func() {
+		// Once gitlab-rails is done handling the request, we are supposed to
+		// delete the upload from its temporary location.
+		<-outerCtx.Done()
+		u.strategy.Delete()
 	}()
-}
 
-func (u *uploader) trackUploadTime() {
-	started := time.Now()
-	<-u.ctx.Done()
+	uploadCtx, cancelFn := context.WithDeadline(outerCtx, deadline)
+	defer cancelFn()
 
-	if u.metrics {
-		objectStorageUploadTime.Observe(time.Since(started).Seconds())
+	var hasher hash.Hash
+	if u.checkETag {
+		hasher = md5.New()
+		reader = io.TeeReader(reader, hasher)
 	}
-}
 
-func (u *uploader) cleanup(ctx context.Context, uploadDone chan struct{}) {
-	// wait for the upload to finish
-	<-u.ctx.Done()
+	cr := &countReader{r: reader}
+	if err := u.strategy.Upload(uploadCtx, cr); err != nil {
+		return cr.n, err
+	}
 
-	<-uploadDone
-	if u.uploadError != nil {
-		if u.metrics {
-			objectStorageUploadRequestsRequestFailed.Inc()
+	if u.checkETag {
+		if err := compareMD5(hexString(hasher), u.strategy.ETag()); err != nil {
+			log.ContextLogger(uploadCtx).WithError(err).Error("error comparing MD5 checksum")
+			return cr.n, err
 		}
-		u.strategy.Abort()
-		return
 	}
 
-	// We have now successfully uploaded the file to object storage. Another
-	// goroutine will hand off the object to gitlab-rails.
-	<-ctx.Done()
-
-	// gitlab-rails is now done with the object so it's time to delete it.
-	u.strategy.Delete()
+	return cr.n, nil
 }
 
 func compareMD5(local, remote string) error {
@@ -188,3 +100,14 @@ func compareMD5(local, remote string) error {
 
 	return nil
 }
+
+type countReader struct {
+	r io.Reader
+	n int64
+}
+
+func (cr *countReader) Read(p []byte) (int, error) {
+	nRead, err := cr.r.Read(p)
+	cr.n += int64(nRead)
+	return nRead, err
+}

internal/upload/uploads_test.go

@@ -123,7 +123,7 @@ func TestUploadHandlerRewritingMultiPartData(t *testing.T) {
 			require.Equal(t, hash, r.FormValue("file."+algo), "file hash %s", algo)
 		}
 
-		require.Len(t, r.MultipartForm.Value, 12, "multipart form values")
+		require.Len(t, r.MultipartForm.Value, 11, "multipart form values")
 
 		w.WriteHeader(202)
 		fmt.Fprint(w, "RESPONSE")

upload_test.go

@@ -79,7 +79,7 @@ func uploadTestServer(t *testing.T, extraTests func(r *http.Request)) *httptest.
 
 		require.NoError(t, r.ParseMultipartForm(100000))
 
-		const nValues = 11 // file name, path, remote_url, remote_id, size, md5, sha1, sha256, sha512, gitlab-workhorse-upload, etag for just the upload (no metadata because we are not POSTing a valid zip file)
+		const nValues = 10 // file name, path, remote_url, remote_id, size, md5, sha1, sha256, sha512, gitlab-workhorse-upload for just the upload (no metadata because we are not POSTing a valid zip file)
 		require.Len(t, r.MultipartForm.Value, nValues)
 
 		require.Empty(t, r.MultipartForm.File, "multipart form files")